Palo Verde TR 32279 BCPR2022-0019 - Soils Report Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 1
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
Soil Corrosivity Evaluation
Report
for
Palo Verde Lot7
July 25, 2022
Prepared for:
Thuc Miyashiro, P.E.
Williams Homes
24911 Avenue Stanford,
Santa Clarita, CA 91355
tmiyashiro@williamshomes.com
Project X Job #: S220718Z
Client Job or PO #: X
BCPR2022-0019
PALO VERDE / PLAN 3 TRACT
CONSTRUCTION PLANS
03/08/2023
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 2
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
Contents
1 Executive Summary ................................................................................................................ 4
2 Corrosion Control Recommendations..................................................................................... 5
2.1 Cement ............................................................................................................................. 5
2.2 Steel Reinforced Cement/ Cement Mortar Lined & Coated (CML&C) .......................... 5
2.3 Stainless Steel Pipe/Conduit/Fittings ............................................................................... 6
2.4 Steel Post Tensioning Systems ......................................................................................... 7
2.5 Steel Piles ......................................................................................................................... 8
2.5.1 Expected Corrosion Rate of Steel and Zinc in disturbed soil ................................... 9
2.5.2 Expected Corrosion Rate of Steel and Zinc in Undisturbed soil .............................. 9
2.6 Steel Storage tanks ........................................................................................................... 9
2.7 Steel Pipelines ................................................................................................................ 10
2.8 Steel Fittings ................................................................................................................... 12
2.9 Ductile Iron (DI) & Cast Iron Fittings ........................................................................... 12
2.10 Ductile Iron & Cast Iron Pipe ..................................................................................... 13
2.11 Copper Materials ........................................................................................................ 15
2.11.1 Copper Pipes ........................................................................................................... 15
2.11.2 Brass Fittings .......................................................................................................... 15
2.11.3 Bare Copper Grounding Wire ................................................................................. 16
2.12 Aluminum Pipe/Conduit/Fittings ............................................................................... 17
2.13 Carbon Fiber or Graphite Materials............................................................................ 17
2.14 Plastic and Vitrified Clay Pipe ................................................................................... 17
3 CLOSURE ............................................................................................................................ 18
4 Soil analysis lab results ......................................................................................................... 19
5 Corrosion Basics ................................................................................................................... 23
5.1 Pourbaix Diagram – In regards to a material’s environment ......................................... 23
5.2 Galvanic Series – In regards to dissimilar metal connections ........................................ 23
5.3 Corrosion Cell ................................................................................................................ 26
5.4 Design Considerations to Avoid Corrosion ................................................................... 27
5.4.1 Testing Soil Factors (Resistivity, pH, REDOX, SO, CL, NO3, NH3) ................... 27
5.4.2 Proper Drainage ...................................................................................................... 28
5.4.3 Avoiding Crevices .................................................................................................. 28
5.4.4 Coatings and Cathodic Protection ........................................................................... 29
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 3
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
5.4.5 Good Electrical Continuity ..................................................................................... 31
5.4.6 Bad Electrical Continuity ........................................................................................ 32
5.4.7 Corrosion Test Stations ........................................................................................... 32
5.4.8 Excess Flux in Plumbing ........................................................................................ 33
5.4.9 Landscapers and Irrigation Sprinkler Systems ....................................................... 33
5.4.10 Roof Drainage splash zones .................................................................................... 33
5.4.11 Stray Current Sources ............................................................................................. 34
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 4
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
1 Executive Summary
A corrosion evaluation of the soils at Palo-Verde-Lot7 was performed to provide corrosion
control recommendations for general construction materials. The site is located at Palo Verde
Project, La Quinta, CA, (33°37'48.1"N 116°15'28.0"W). Twelve ( 12 ) samples were tested to a
depth of 4.0 ft. Site ground water and topography information was provided by Williams
Homes. Groundwater depth was determined to be 25 feet below finished grade.
Every material has its weakness. Aluminum alloys, galvanized/zinc coatings, and copper alloys
do not survive well in very alkaline or very acidic pH environments. Copper and brasses do not
survive well in high nitrate or ammonia environments. Steels and irons do not survive well in
low soil resistivity and high chloride environments. High chloride environments can even
overcome and attack steel encased in normally protective concrete. Concrete does not survive
well in high sulfate environments. And nothing survives well in high sulfide and low redox
potential environments with corrosive bacteria. This is why Project X tests for these 8 factors to
determine a soil's corrosivity towards various construction materials. Depending solely on soil
resistivity or Caltrans corrosion guidelines (which concentrate on concrete/steel highways),
will over-simplify descriptions as corrosive or non-corrosive. This approach will not detect
these other factors attacking other metals because it is possible to have bad levels of
corrosive ions and still have greater than 1,100 ohm-cm soil resistivity. We have observed
this fact on thousands of soil samples tested in our laboratory.
It should not be forgotten that import soil should also be tested for all factors to avoid making
your site more corrosive than it was to begin with.
The recommendations outlined herein are not a substitute for any design documents previously
prepared for the purpose of construction and apply only to the depth of samples collected.
Soil samples were tested for minimum resistivity, pH, chlorides, sulfates, ammonia, nitrates,
sulfides and redox.
As-Received soil resistivities ranged between 14,070 ohm-cm and 67,000.0 ohm-cm. This
data would be similar to a Wenner 4 pin test in the field and used in the design of a cathodic
protection or grounding bed system. This resistivity can change seasonally depending on the
weather and moisture in the ground. This reading alone can be misleading because condensation
or minor water leaks will occur underground along pipe surfaces creating a saturated soil
environment in the trench on infrastructure surfaces. This is why minimum or saturated soil
resistivity measurements are more important than as-received resistivities.
Saturated soil resistivities ranged between 422 ohm-cm to 2,345 ohm-cm. The worst of these
values is considered to be severely corrosive to general metals.
PH levels ranged between 7.2 to 8.6 pH. PH levels were determined to be at levels not
detrimental to copper or aluminum alloys. The pH of these samples can allow corrosion of steel
and iron in moist environments.
Chlorides ranged between 20 mg/kg to 952 mg/kg.
At all lots other than at lots 13 thru 19, Chloride levels in these samples are low and may cause
insignificant corrosion of metals. At lots 13 thru 19, Chloride levels in these samples are enough
to cause significant corrosion in metals in soil and in cement. Cement encased metals will
require protection from chloride intrusion from soil.
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 5
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
Sulfates ranged between 41 mg/kg to 743 mg/kg. Sulfate levels in these samples are negligible
for corrosion of cement. Any type of cement can be used that does not contain encased metal.
Ammonia ranged between 0.7 mg/kg to 123.3 mg/kg. Nitrates ranged between 1.7 mg/kg to
347.6 mg/kg. Concentrations of these elements were high enough to cause accelerated corrosion
of copper and copper alloys such as brass.
Sulfides presence was determined to be negative. REDOX ranged between + 139 mV to + 187
mV. The probability of corrosive bacteria was determined to be low due to the sulfide and
positive REDOX levels determined in these samples.
2 Corrosion Control Recommendations
The following recommendations are based upon the results of soil testing.
2.1 Cement
The highest reading for sulfates was 743 mg/kg or 0.0743 percent by weight.
Per ACI 318-14, Table 19.3.1.1, sulfate levels in these samples categorized as S0 and are
negligible for corrosion of metals and cement. Per ACI 318-14 Table 19.3.2.1 any type of
cement not containing steel or other metal can be used.
2.2 Steel Reinforced Cement/ Cement Mortar Lined & Coated (CML&C)
Chlorides in soil can overcome the corrosion inhibiting property of cement for steel, as it can
also break through passivated surfaces of aluminum and stainless steels.0F
1,
1F
2 The highest
concentration of chlorides was 952 mg/kg.
At all lots except lots 13 thru 19, Chloride levels in these samples are not significantly corrosive
to metals not in tension. Standard cement cover may be used in these soils.
At lots 13 thru 19, Chloride levels in these samples are enough to cause significant corrosion of
metals in soil and in cement. Corrosion protection options can be one of the following:
1) Maintain 3 inches of concrete cover between any embedded steel / hardware extending or
existing 8 inches below finished floor. Use Type II cement + Pozzolan or slag cement
per ACI 318-14 Table 19.3.2.1 to continue use of steel materials encased in cement2F
3. #5
rebar or Anchor bolts with diameters of 5/8-inch or less require a minimum of 1.5 inches
of cover per ACI 222.3R-5 Table 2.1, or
2) For any embedded steel/hardware extending or existing below 8 inches of finished floor
(FF) where recommended concrete cover is not possible, use epoxy coating such as
1 Design Manual 303: Cement Cylinder Pipe. Ameron. p.65 2 Chapter 19, Table 1904.2.2(1), 2012 International Building Code 3 Standard Requirements for Design of Shallow PT Cement foundations on Expansive soil
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 6
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
Purple fusion bonded epoxy (FBE) (ASTM A934) or equivalent or powder coated steel
with minimum 60 micron (2-3 mil) thick coating3F
4.
3) Provide waterproof coating with minimum 10 mil thickness to cement that is in contact
with soil, or
4) Prevent contact between cement and soil using minimum 10 mil thick vapor barrier with
joints overlapped at least 6 inches & taped, also sealing around plumbing & conduits.
Barrier per ASTM E1745 installed in accordance with ASTM E1643. Class B barriers
should be installed with capillary break layer, Class A barriers do not require capillary
break layer. Or,
5) Use 5,000 psi cement designed per ACI 318-14 Chapter 19 Table 19.3.1.1 per C2
category which exceeds the exposure class for this project, or
6) Mix a chloride corrosion inhibitor such as DCI or equivalent into the cement with cement
mix designed to protect embedded steel and iron that should be based on 1) Chloride
content of 952 ppm in the soil, 2) desired service life, 3) cement cover. We defer to the
manufacturer of the chloride inhibitor for determination of the proper admixture ratio to
cement, or
7) Apply Cathodic Protection
Though soils at some locations are significantly corrosive to various metals, per ACI 318-14
Chapter 19 Table 19.3.1.1, all slabs on this site exposure categories and class for Corrosion
Protection of Reinforcement (C) would be considered C1 as Concrete exposed to moisture
[mud/rain] (slab sides and bottom) but not to an external source of chlorides. Though there are
chlorides in the soil, ACI 318’s definition of “external source of chlorides” consists of deicing
chemicals, salt, brackish water, seawater, or spray from these sources. The chloride levels in
seawater are typically over 19,000 mg/L or 19,000 ppm.
When concrete is tested for water-soluble chloride ion content, the tests should be made at an age
of 28 to 42 days. The limits in Per ACI 318-14 Table 5.3.2.1 are to be applied to chlorides
contributed from the concrete ingredients, not those from the environment surrounding the
concrete.4F
5
2.3 Stainless Steel Pipe/Conduit/Fittings
Stainless steels derive their corrosion resistance from their chromium content and oxide layer
which needs oxygen to regenerate if damaged. Thus stainless steel is not good for deep soil
applications where oxygen levels are extremely low. Stainless steels should not be installed
deeper than a plant root zone. Stainless steels typically have the same nobility as copper on the
galvanic series and can be connected to copper. If stainless steel must be used, it must be
backfilled with soil having greater than 10,000 ohm-cm resistivity and excellent drainage. 304
4 Manish Kumar Bhadu, Akshya Kumar Guin, Veena Singh, Shyam K. Choudhary, "Corrosion Study of Powder-
Coated Galvanised Steel", International Scholarly Research Notices, vol. 2013, Article ID 464710, 9 pages, 2013
5 ACI 381-14., BUILDING CODE REQUIREMENTS FOR STRUCTURAL CONCRETE (ACI 318-14) AND
COMMENTARY (ACI 318R-14)
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 7
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
Stainless steel will also corrode if in contact with carbon materials such as activated carbon.
Stainless steel welds should be pickled.
The soil at this site has low probability for anaerobic corrosive bacteria and moderate chloride
levels. Per Nickel Institute guidelines, 316 Stainless steels should only be used in these soils.
2.4 Steel Post Tensioning Systems
The proper sealing of stressing holes is of utmost importance in PT Systems. Cut off excess
strand 1/2" to 3/4" back in the hole. Coat or paint exposed anchorage, grippers, and stub of
strands with "Rust-o-leum" or equal. After tendons have been coated, the cement contractor
shall dry pack blockouts within ten (10) days. A non-shrink, non-metallic, non-porous moisture-
insensitive grout (Master EMACO S 488 or equivalent), or epoxy grout shall be used for this
purpose. If an encapsulated post-tension system is used, regular non-shrink grout can be used.
At lots 13 thru 19, Soil with high chloride levels is considered an aggressive environment for
post-tensioning strands and anchors. Due to the high chloride levels determined at lots 13 thru
19, implement all of the following measures:5F
6,
6F
7,
7F
8
1) Completely encapsulate the tendon and anchor with polyethylene to create a watertight
seal. Epoxy or powder coated hardware would be equivalent to polyethylene coated and
impermeable waterproofing system.
2) Add grease caps to the cut strand at live end anchors to provide extra protection against
corrosion due to high chloride concentrations.
3) All components exposed to the job site should be protected within one working day after
their exposure during installation.
4) Ensure the minimum cement cover over the tendon tail is 1-inch, or greater if required by
the applicable building code.
5) Caps and sleeves should be installed within one working day after the cutting of the
tendon tails and acceptance of the elongation records by the engineer.
6) Inspect the following to ensure the encapsulated system is completely watertight:
a) Sheathing: Verify that all damaged areas, including pin-holes, are repaired.
b) Stressing tails: After removal, ensure they are cut to a length for proper installation of
P/T coating filled end caps.
c) End caps: Ensure proper installation before patching the pocket former recesses.
d) Patching: Ensure the patch is of an approved material and mix design, and installed
void-free.
e) Limit the access of direct runoff onto the anchorage area by designing proper
drainage.
6 Standard Requirements for Design and Analysis of Shallow Post-Tensioned Concrete Foundations on Expansive
Soils, PTI DC10.5-12,Table 4.1, pg 16 7 Specification for Unbonded Single Strand Tendons. Post-Tensioning Institute (PTI), Phoenix, AZ, 2000. 8 ACI 423.6-01: Specification for Unbonded Single Strand Tendons. American Cement Institute (ACI), 2001
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 8
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
f) Provide at least 2 inches of space between finish grade and the anchorage area, or
more if required by applicable building codes.
At other lots other than lots 13 thru 19, Due to the moderate chloride concentration measured on
samples obtained from this site, post-tensioned slabs should be protected in accordance with soil
considered normal (non-corrosive).8F
9,
9F
10 Additionally, add grease caps to the cut strand at live end
anchors to provide protection against corrosion due to moderate chloride levels.
2.5 Steel Piles
Steel piles are most susceptible to corrosion in disturbed soil where oxygen is available. Further,
a dissimilar environment corrosion cell would exist between the steel embedded in cement, such
as pile caps and the steel in the soil. In the cell, the steel in the soil is the anode (corroding
metal), and the steel in cement is the cathode (protected metal). This cell can be minimized by
coating the part of the steel piles that will be embedded in cement to prevent contact with cement
and reinforcing steel.
Piles driven into soils without disturbing soils will avoid oxygen introduction and low corrosion
rates unless there is a probability for corrosive anaerobic bacteria. Galvanized steel's zinc
coating can provide significant protection for driven piles. In corrosive soils in which normal
zinc coatings are not enough, the life of piles can be extended by increasing zinc coating
thickness, using sacrificial metal, or providing a combination of epoxy coatings and cathodic
protection. Corrosion has been observed to be extremely localized even at and below
underground water tables. Pit depths of this magnitude do not have an appreciable effect on the
strength or useful life of piling structures because the reduction in pile cross section is not
significant.10F
11 Pitting is of more importance to pipes transporting liquids or gases which should
not be leaked into the ground.
The following recommendations are recommended to achieve desired life. We defer to structural
engineers to use our estimated corrosion rates and to choose from the corrosion control options
listed below.
1) Sacrificial metal by use of thicker piles per non-disturbed soil corrosion rates, or
2) Galvanized steel piles per non-disturbed soil corrosion rates, or
3) Combination of galvanized and sacrificial metal per non-disturbed soil corrosion rates, or
4) For no loss of metal, coat entire pile with abrasion resistant epoxy coating such as 3M
Scotchkote 323, or PowercreteDD, or equivalent, or
5) Use high yield steel which will corrode at the same rate as mild steel but have greater
yield strength and thus be able to suffer more material loss than mild steel.
9 Standard Requirements for Design and Analysis of Shallow Post-Tensioned Concrete Foundations on Expansive
Soils, PTI DC10.5-12,Table 4.1, pg 16 10 Specification for Unbonded Single Strand Tendons. Post-tensioning Institute (PTI), Phoenix, AZ, 2000.
11 Melvin Romanoff, Corrosion of Steel Pilings in Soils, National Bureau of Standards Monograph 58, pg 20.
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 9
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
2.5.1 Expected Corrosion Rate of Steel and Zinc in disturbed soil
In general, the corrosion rate of metals in soil depends on the electrical resistivity, the elemental
composition, and the oxygen content of the soil. Soils can vary greatly from one acre to the next,
especially at earthquake faults. The better a soil is for farming; the easier it will be for corrosion
to take place. Expansive soils will also be considered disturbed simply because of their nature
from dry to wet seasons.
In Melvin Romanoff’s NBS Circular 579, the corrosion rates of carbon steels and various metals
was studied over long term periods. Various metals were placed in various soil types to gather
corrosion rate data of all metals in all soil types. Samples were collected and material loss
measured over the course of 20 years in some sites. The following corrosion rates were
estimated by comparing the worst results of soils tested with similar soils in Romanoff’s studies
and Highway Research Board’s publications.11F
12 The corrosion rate of zinc in disturbed soils is
determined per Romanoff studies and King Nomograph.12F
13
Expected Corrosion Rate for Steel = 1.95 mils/year for one sided attack
Expected Corrosion Rate for Zinc = 0.71 mils/year for one sided attack.
Note: 1 mil = 0.001 inch
In undisturbed soils, a corrosion rate of 1.00 mil/year for steel is expected with little change in
the corrosion rate of zinc due to it’s low nobility in the galvanic series.
Per CTM 643: Years to perforation of corrugated galvanized steel culverts
• 26.6 Years to Perforation for a 18 gage metal culvert
• 34.6 Years to Perforation for a 16 gage metal culvert
• 42.6 Years to Perforation for a 14 gage metal culvert
• 58.5 Years to Perforation for a 12 gage metal culvert
• 74.5 Years to Perforation for a 10 gage metal culvert
• 90.5 Years to Perforation for a 8 gage metal culvert
2.5.2 Expected Corrosion Rate of Steel and Zinc in Undisturbed soil
Expected Corrosion Rate for Steel = 1.00 mils/year for one sided attack
Expected Corrosion Rate for Zinc = 0.71 mils/year for one sided attack.
Note: 1 mil = 0.001 inch
2.6 Steel Storage tanks
Underground fuel tanks must be constructed and protected in accordance with California
Underground Storage Tank Regulations, CCR, Title 23, Division 3, Chapter 16. Metals should
be protected with cathodic protection or isolated from backfill material with an epoxy coating.
12 Field test for Estimating Service Life of Corrugated Metal Culverts, J.L. Beaton, Proc. Highway Research Board,
Vol 41, P. 255, 1962 13 King, R.A. 1977, Corrosion Nomograph, TRRC Supplementary Report, British Corrosion Journal
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 10
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
2.7 Steel Pipelines
Though a site may not be corrosive in nature at the time of construction, installation of
corrosion test stations and electrical continuity joint bonding should be performed during
construction so that future corrosion inspections can be performed. If steel pipes with gasket
joints or other possibly non-conductive type joints are installed, their joints should be bonded
across by welding or pin brazing a #8 AWG copper strand bond cable. Electrical continuity is
necessary for corrosion inspections and for cathodic protection.
Corrosion test stations should be installed every 1,000 feet of pipeline.
Test stations shall have two #8 HMWPE copper strand wire test leads welded or pin brazed to
the underground pipe, brought up into the test station hand hole and marked CTS. Wires should
be brought into test station hand hole at finished grade with 12 inches of wire coiled within test
station.
At isolation joints and pipe casings, 4 wire test stations shall be installed using #8 HMWPE
copper strand wire test leads. Use different color wires to distinguish which wires are bonded to
one side of isolation joint or to casing. Wires should be brought into test station hand hole at
finished grade with 12 inches of wire coiled within test station.
Prevent dissimilar metal corrosion cells per NACE SP0286:
1) Electrically isolate dissimilar metal connections
2) Electrically isolate dissimilar coatings (Epoxy vs CML&C) segments connections
3) Electrically isolate river crossing segments
4) Electrically isolate freeway crossing segments
5) Electrically isolate old existing pipelines from new pipelines
6) Electrically isolate aboveground and underground pipe segments with flange isolation
joint kits per NACE SP0286 to avoid galvanic corrosion cells. These are especially
important for fire risers.
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 11
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
Figure 1- Fire Riser Detail: Install Isolation joint at red arrow
The corrosivity at this site is corrosive to steel. Any piping that must be jack-bored should use
abrasion resistant epoxy coating such as 3M Scotchkote 323, or PowercreteDD, or equivalent.
The corrosion control options for this site are as follows:
1) Apply impermeable dielectric coating such as minimum 10 mil thick polyethylene, and
install cathodic protection system per NACE SP0169, or
2) Wax tape per AWWA C217, or
3) Coal tar enamel per AWWA C203, or
4) Fusion bonded epoxy per AWWA C213, or
5) For bare steel surfaces, such as welded pipe joints, apply 3 inch thick field coating of
Type II cement or high pH slurry that will maintain pH higher than 12. Cement is both a
corrosion inhibitor and a coating for ferrous metals. Cement naturally holds a pH of 12 or
higher for many years if not exposed to high levels of carbon dioxide. (For CML&C
pipes, CML&C factory applied 3/4 inch thick coating is equivalent and needs no extra
thickness added.)
It is critical for the life of the pipe that the protective wrap contains no openings or holes.
Prevent damage to the protective sleeve during backfilling of the pipe trench. Penetrations of
any kind within these or other protective materials generally leads to accelerated corrosion
failure due to the fact that the corrosion attack is concentrated at the location of these
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 12
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
penetrations. Cathodic protection will protect these defects. The better the coating, the less
expensive a cathodic protection system will be in anode material and power requirement if
needed.
2.8 Steel Fittings
The corrosivity at this site is corrosive to steel. The corrosion control options for this site are as
follows:
1) Apply impermeable dielectric coating such as minimum 10 mil thick polyethylene, and
install cathodic protection system per NACE SP0169, or
2) Tape coating system per AWWA C214, or
3) Wax tape per AWWA C217, or
4) Coal tar enamel per AWWA C203, or
5) Fusion bonded epoxy per AWWA C213
6) Apply 3 inch coating of Type II cement or high pH slurry that will maintain pH higher
than 12. Cement is both a corrosion inhibitor and a coating for ferrous metals. Cement
naturally holds a pH of 12 or higher for many years if not exposed to high levels of
carbon dioxide.
It is critical for the life of the metal that the protective wrap contains no openings or holes.
Prevent damage to the protective sleeve during backfilling of the pipe trench. Penetrations of
any kind within these or other protective materials generally leads to accelerated corrosion
failure due to the fact that the corrosion attack is concentrated at the location of these
penetrations. Cathodic protection will protect these defects. The better the coating, the less
expensive a cathodic protection system will be in anode material and power requirement if
needed.
2.9 Ductile Iron (DI) & Cast Iron Fittings
AWWA C105 developed a 10 point system to classify sites as aggressive or non-aggressive to
ductile iron materials. The 10-point system does not, and was never intended to, quantify the
corrosivity of a soil. It is a tool used to distinguish nonaggressive from aggressive soils relative
to iron pipe. Soils <10 points are considered nonaggressive to iron pipe, whereas soils ≥10
points are considered aggressive. A 15 and a 20 point soil are both considered aggressive to iron
pipe, however, because of the nature of the soil parameters measured, the 20 point soil may not
necessarily be more aggressive than the 15 point soil. The criterion is based upon soil
resistivities, soil drainage, pH, sulfide presence, and reduction-oxidation (REDOX) potential.
The soil samples tested for this site resulted in a score of 14 out of 25.5. A score greater or equal
to 10 points classifies soils as aggressive to iron materials. The black coating on iron pipes is
purely for aesthetic purposes and should not be relied upon for corrosion protection.13F
14
The corrosivity at this site is corrosive to iron. The corrosion control options for this site are as
follows:
14 https://www.dipra.org/ductile-iron-pipe-resources/frequently-asked-questions/corrosion-control
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 13
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
1) Apply impermeable dielectric coating such as minimum 10 mil thick polyethylene, and
install cathodic protection system per NACE SP0169, or
2) Wax tape per AWWA C217, or
3) Coal tar enamel per AWWA C203, or
4) Fusion bonded epoxy per AWWA C213
5) Apply standard concrete cover of Type II cement or high pH slurry that will maintain pH
higher than 12. Cement is both a corrosion inhibitor and a coating for ferrous metals.
Cement naturally holds a pH of 12 or higher for many years if not exposed to high levels
of carbon dioxide.
It is critical for the life of the metal that the protective wrap contains no openings or holes.
Prevent damage to the protective sleeve during backfilling of the pipe trench. Penetrations of
any kind within these or other protective materials generally leads to accelerated corrosion
failure due to the fact that the corrosion attack is concentrated at the location of these
penetrations. Cathodic protection will protect these defects. The better the coating, the less
expensive a cathodic protection system will be in anode material and power requirement if
needed.
2.10 Ductile Iron & Cast Iron Pipe
AWWA C105 developed a 10 point system to classify sites as aggressive or non-aggressive to
ductile iron materials. The 10-point system does not, and was never intended to, quantify the
corrosivity of a soil. It is a tool used to distinguish nonaggressive from aggressive soils relative
to iron pipe. Soils <10 points are considered nonaggressive to iron pipe, whereas soils ≥10
points are considered aggressive. A 15 and a 20 point soil are both considered aggressive to iron
pipe, however, because of the nature of the soil parameters measured, the 20 point soil may not
necessarily be more aggressive than the 15 point soil. The criterion is based upon soil
resistivities, soil drainage, pH, sulfide presence, and reduction-oxidation (REDOX) potential.
The soil samples tested for this site resulted in a score of 14 out of 25.5. A score greater or equal
to 10 points classifies soils as aggressive to iron materials. The black coating on iron pipes is
purely for aesthetic purposes and should not be relied upon for corrosion protection.14F
15
Though a site may not be corrosive in nature at the time of construction, installation of
corrosion test stations and electrical continuity joint bonding should be performed during
construction so that future corrosion inspections can be performed. If steel pipes with gasket
joints or other possibly non-conductive type joints are installed, their joints should be bonded
across by welding or pin brazing a #8 AWG copper strand bond cable. Electrical continuity is
necessary for corrosion inspections and for cathodic protection. If using thermite, perform one
test bond using a half-charge then pressure test to confirm excess heat and pinholes were
not created.
Pea gravel is used by plumbers to lay pipes and establish slopes. If the gravel has more than 200
ppm chlorides or is not tested, a 25 mil plastic should be placed between the gravel and pipe to
avoid corrosion.
15 https://www.dipra.org/ductile-iron-pipe-resources/frequently-asked-questions/corrosion-control
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 14
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
Corrosion test stations should be installed every 1,000 feet of pipeline.
Test stations shall have two #8 HMWPE copper strand wire test leads welded or pin brazed to
the underground pipe, brought up into the test station hand hole and marked CTS. Wires should
be brought into test station hand hole at finished grade with 12 inches of wire coiled within test
station.
At isolation joints and pipe casings, 4 wire test stations shall be installed using #8 HMWPE
copper strand wire test leads. Use different color wires to distinguish which wires are bonded to
one side of isolation joint or to casing. Wires should be brought into test station hand hole at
finished grade with 12 inches of wire coiled within test station.
Prevent dissimilar metal corrosion cells per NACE SP0286:
1) Electrically isolate dissimilar metal connections
2) Electrically isolate dissimilar coatings (Epoxy vs CML&C) segments connections
3) Electrically isolate river crossing segments
4) Electrically isolate freeway crossing segments
5) Electrically isolate old existing pipelines from new pipelines
6) Electrically isolate aboveground and underground pipe segments with flange isolation
joint kits per NACE SP0286. These are especially important for fire risers.
The corrosivity at this site is corrosive to iron. Any piping that must be jack-bored should use
abrasion resistant epoxy coating such as 3M Scotchkote 323, or PowercreteDD, or equivalent.
The corrosion control options for this site are as follows:
1) Apply impermeable dielectric coating such as minimum 10 mil thick polyethylene, and
install cathodic protection system per NACE SP0169, or
2) Wax tape per AWWA C217, or
3) Coal tar enamel per AWWA C203, or
4) Fusion bonded epoxy per AWWA C213, or
5) Apply 3 inch coating of Type II cement or high pH slurry that will maintain pH higher
than 12. Cement is both a corrosion inhibitor and a coating for ferrous metals. Cement
naturally holds a pH of 12 or higher for many years if not exposed to high levels of
carbon dioxide.
It is critical for the life of the metal that the protective wrap contains no openings or holes.
Prevent damage to the protective sleeve during backfilling of the pipe trench. Penetrations of
any kind within these or other protective materials generally leads to accelerated corrosion
failure due to the fact that the corrosion attack is concentrated at the location of these
penetrations. Cathodic protection will protect these defects. The better the coating, the less
expensive a cathodic protection system will be in anode material and power requirement if
needed.
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 15
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
2.11 Copper Materials
Copper is an amphoteric material which is susceptible to corrosion at very high and very low pH.
It is one of the most noble metals used in construction thus typically making it a cathode when
connected to dissimilar metals. Copper’s nobility can change with temperature, similar to the
phenomenon in zinc. When zinc is at room temperature, it is less noble than steel and can
provide cathodic protection to steel. But when zinc is at a temperature above 140F such as in a
water heater, it becomes more noble than the steel and the steel becomes the sacrificial anode.
This is why zinc is not used in steel water heaters or boilers. Cold copper has one native
potential, but when heated it develops a more electronegative electro-potential aka open circuit
potential. Thus hot and cold copper pipes should be electrically isolated from each other to
avoid creation of a thermo-galvanic corrosion cell.
2.11.1 Copper Pipes
The lowest pH for this area was measured to be 7.2. Copper is greatly affected by pH, ammonia
and nitrate concentrations15F
16. The highest nitrate concentration was 347.6 mg/kg and the highest
ammonia concentration was 123.3 mg/kg at this site.
These soils were determined to be corrosive to copper and copper alloys such as brass.
Aboveground, underground, cold water and hot water pipes should be electrically isolated from
each other by use of dielectric unions and plastic in-wall pipe supports per NACE SP0286. The
following are corrosion control options for underground copper water pipes.
1) Run copper pipes within PVC pipes to prevent soil contact, or
2) Cover piping with a 20 mil epoxy coating, or 8-mil polyethylene sleeve, or encase in
double 4-mil thick polyethylene sleeves free of scratches and defects then backfill with
clean sand with 2 inch minimum cover above and below tubing. Backfill should have a
pH between 6 and 8 with electrical resistivity greater than 2,000 ohm-cm
3) Cover copper pipes with minimum 8 mil polyethylene sleeve or incase in double 4-mil
thick polyethylene sleeves over a suitable primer and apply cathodic protection per
NACE SP0169
It is critical for the life of the metal that the protective wrap contains no openings or holes.
Prevent damage to the protective sleeve during backfilling of the pipe trench. Penetrations of
any kind within these or other protective materials generally leads to accelerated corrosion
failure due to the fact that the corrosion attack is concentrated at the location of these
penetrations. Cathodic protection will protect these defects. The better the coating, the less
expensive a cathodic protection system will be in anode material and power requirement if
needed.
2.11.2 Brass Fittings
Brass fittings should be electrically isolated from dissimilar metals by use of dielectric unions or
isolation joint kits per NACE SP0286.
These soils were determined to be corrosive to copper and copper alloys such as brass.
16 Corrosion Data Handbook, Table 6, Corrosion Resistance of copper alloys to various environments, 1995
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 16
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
The following are corrosion control options for underground brass.
1) Prevent soil contact by use of impermeable coating system such as wax tape, or
2) Prevent soil contact by use of a 20 mil epoxy coating free of scratches and defects and
backfill with clean sand with 4 inch minimum cover above and below brass. Backfill
should have a pH between 6 and 8 with electrical resistivity greater than 2,000 ohm-cm,
or
3) Cover brass with minimum 10 mil polyethylene sleeve over a suitable primer and apply
cathodic protection per NACE SP0169
It is critical for the life of the metal that the protective wrap contains no openings or holes.
Prevent damage to the protective sleeve during backfilling of the pipe trench. Penetrations of
any kind within these or other protective materials generally leads to accelerated corrosion
failure due to the fact that the corrosion attack is concentrated at the location of these
penetrations. Cathodic protection will protect these defects. The better the coating, the less
expensive a cathodic protection system will be in anode material and power requirement if
needed.
2.11.3 Bare Copper Grounding Wire
It is assumed that corrosion will occur at all sides of the bare wire, thus the corrosion rate is
calculated as a two sided attack determining the time it takes for the corrosion from two sides to
meet at the center of the wire. The estimated life of bare copper wire for this site is the
following:16F
17
Size (AWG) Diameter (mils) Est. Time to penetration (Yrs)
14 64.1 5.5
13 72 6.2
12 80.8 7.0
11 90.7 7.8
10 101.9 8.8
9 114.4 9.9
8 128.5 11.1
7 144.3 12.4
6 162 14.0
5 181.9 15.7
4 204.3 17.6
3 229.4 19.8
2 257.6 22.2
1 289.3 24.9
If the bare copper wire is being used as a grounding wire connected to less noble metals such as
galvanized steel or carbon steel, the less noble metals will provide additional cathodic protection
to the copper reducing the corrosion rate of the copper.
17 Soil-Corrosion studies 1946 and 1948: Copper Alloys, Lead, and Zinc, Melvin Romanoff, National Bureau of
Standards, Research Paper RP2077, 1950
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 17
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
It is recommended that a corrosion inhibiting and water-repelling coating be applied to
aboveground and belowground copper-to-dissimilar metal connections to reduce risk of
dissimilar corrosion. This can be wax tape, or other epoxy coating.
Tinned copper wiring or laying copper wire in conductive concrete can protect against chemical
attack in soils with high nitrates, ammonia, sulfide and severely low soil electrical resistivity.
2.12 Aluminum Pipe/Conduit/Fittings
Aluminum is an amphoteric material prone to pitting corrosion in environments that are very
acidic or very alkaline or high in chlorides.
Conditions at this site are safe for aluminum.
Aluminum derives its corrosion resistance from its oxide layer which needs oxygen to regenerate
if damaged, similar to stainless steels. Thus aluminum is not good for deep soil applications.
Since aluminum corrodes at very alkaline environments, it cannot be encased or placed against
cement or mortar such as brick wall mortar up against an aluminum window frame.
Aluminum is also very low on the galvanic series scale making it most likely to become a
sacrificial anode when in contact with dissimilar metals in moist environments. Avoid electrical
continuity with dissimilar metals by use of insulators, dielectric unions, or isolation joints per
NACE SP0286. Pooling of water at post bottoms or surfaces should be avoided by integrating
good drainage.
2.13 Carbon Fiber or Graphite Materials
Carbon fiber or other graphite materials are extremely noble on the galvanic series and should
always be electrically isolated from dissimilar metals. They can conduct electricity and will
create corrosion cells if placed in contact within a moist environment with any metal.
2.14 Plastic and Vitrified Clay Pipe
No special precautions are required for plastic and vitrified clay piping from a corrosion
viewpoint.
Protect all metallic fittings and pipe restraining joints with wax tape per AWWA C217, cement if
previously recommended, or epoxy.
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 18
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
3 CLOSURE
In addition to soils chemistry and resistivity, another contributing influence to the corrosion of
buried metallic structures is stray electrical currents. These electrical currents flowing through
the earth originate from buried electrical systems, grounding of electrical systems in residences,
commercial buildings, and from high voltage overhead power grids. Therefore, it is imperative
that the application of protective wraps and/or coatings and electrical isolation joints be properly
applied and inspected.
It is the responsibility of the builder and/or contractor to closely monitor the installation of such
materials requiring protection in order to assure that the protective wraps or coatings are not
damaged.
The recommendations outlined herein are in conformance with current accepted standards of
practice that meet or exceed the provisions of the Uniform Building Code (UBC), the
International Building Code (IBC), California Building Code (CBC), the American Cement
Institute (ACI), Nickel Institute, National Association of Corrosion Engineers (NACE
International), Post-Tensioning Institute Guide Specifications and State of California Department
of Transportation, Standard Specifications, American Water Works Association (AWWA) and
the Ductile Iron Pipe Research Association (DIPRA).
Our services have been performed with the usual thoroughness and competence of the
engineering profession. No other warranty or representation, either expressed or implied, is
included or intended.
Please call if you have any questions.
Respectfully Submitted,
Ed Hernandez, M.Sc., P.E.
Sr. Corrosion Consultant
NACE Corrosion Technologist #16592
Professional Engineer
California No. M37102
ehernandez@projectxcorrosion.com
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 19
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
4 SOIL ANALYSIS LAB RESULTS
Client: Williams Homes
Job Name: Palo-Verde-Lot7
Client Job Number: X
Project X Job Number: S220718Z
July 25, 2022
Unk = Unknown
NT = Not Tested
ND = 0 = Not Detected
mg/kg = milligrams per kilogram (parts per million) of dry soil weight
Chemical Analysis performed on 1:3 Soil-To-Water extract
Anions and Cations tested via Ion Chromatograph except Sulfide.
Method ASTM G51 ASTM
G200
SM 4500-D ASTM
D4327
ASTM
D6919
ASTM
D6919
ASTM
D6919
ASTM
D6919
ASTM
D6919
ASTM
D6919
ASTM
D4327
ASTM
D4327
Bore# / Description Depth pH Redox Sulfide
S2-
Nitrate
NO3-
Ammonium
NH4+
Lithium
Li+
Sodium
Na+
Potassium
K+
Magnesium
Mg2+
Calcium
Ca2+
Fluoride
F2--
Phosphate
PO43-
(ft)(mg/kg)(wt%)(mg/kg)(wt%)(Ohm-cm)(Ohm-cm)(mV)(mg/kg)(mg/kg)(mg/kg)(mg/kg)(mg/kg)(mg/kg)(mg/kg)(mg/kg)(mg/kg)(mg/kg)
HA-1 1.0 301.6 0.0302 188.6 0.0189 38,190 1,206 7.3 166 <0.01 51.1 28.6 0.03 152.9 30.0 18.0 12.0 0.3 2.5
HA-1 4.0 40.8 0.0041 20.2 0.0020 56,950 2,345 8.5 151 <0.01 1.7 0.7 ND 52.9 1.8 11.7 10.2 2.5 4.8
HA-2 1.0 137.0 0.0137 113.0 0.0113 44,220 670 7.6 187 <0.01 39.0 10.3 ND 105.9 14.8 8.9 6.6 1.1 1.9
HA-2 4.0 542.2 0.0542 263.5 0.0263 31,490 1,474 8.4 179 <0.01 263.9 14.8 ND 203.1 51.5 18.1 29.5 0.3 0.7
HA-3 1.0 180.3 0.0180 102.7 0.0103 23,450 670 7.3 173 0.81 153.3 17.8 0.01 91.1 63.6 9.4 16.6 1.8 5.0
HA-3 4.0 742.9 0.0743 327.2 0.0327 28,810 1,139 7.5 179 <0.01 347.6 31.3 0.01 255.4 108.3 15.4 36.7 0.5 0.6
HA-4 1.0 427.8 0.0428 162.2 0.0162 28,140 422 7.2 166 <0.01 161.9 7.2 0.01 158.4 56.9 8.7 21.1 2.4 1.7
HA-4 4.0 326.4 0.0326 952.3 0.0952 14,070 871 7.3 139 <0.01 123.9 56.5 0.01 571.9 51.6 1.3 21.5 3.4 3.0
HA-5 1.0 241.0 0.0241 612.4 0.0612 67,000 737 7.6 158 <0.01 52.8 38.8 ND 339.6 24.5 9.3 18.3 1.2 1.7
HA-5 4.0 404.3 0.0404 295.2 0.0295 40,200 2,345 8.4 159 0.18 346.8 29.2 0.02 205.5 50.0 10.7 20.0 1.6 1.0
HA-6 1.0 156.3 0.0156 82.9 0.0083 16,750 596 8.0 147 <0.01 63.8 19.2 0.02 100.5 28.9 3.5 5.9 0.9 1.7
HA-6 4.0 192.8 0.0193 223.5 0.0224 28,810 1,541 8.6 161 <0.01 118.6 123.3 322.00 1,204.7 3,496.9 1,364.5 2,804.6 11.1 123.6
ASTM
G187
ASTM
D4327
ASTM
D4327
Resistivity
As Rec'd | Minimum
Sulfates
SO42-
Chlorides
Cl-
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 20
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
Figure 2- Site Satellite image
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 21
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
Figure 3- Soil Sample Locations, Palo Verde Project, La Quinta, CA, (33°37'48.1"N
116°15'28.0"W)
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 22
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
Figure 4- Vicinity Map
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 23
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
5 Corrosion Basics
In general, the corrosion rate of metals in soil depends on the electrical resistivity, the elemental
composition, and the oxygen content of the soil. Soils can vary greatly from one acre to the next,
especially at earthquake faults. The better a soil is for farming; the easier it will be for corrosion to
take place. Expansive soils should be considered disturbed simply because of their nature from dry to
wet seasons.
5.1 Pourbaix Diagram – In regards to a material’s environment
All metals are unique and have a weakness. Some metals do not like acidic (low pH) environments.
Some metals do not like alkaline (high pH) environments. Some metals don’t like either high or low
pH environments such as aluminum. These are called amphoteric materials. Some metals become
passivated and do not corrode at high pH environments such as steel. These characteristics are
documented in Marcel Pourbaix’s book “Atlas of electrochemical equilibria in aqueous solutions”
In the mid 1900’s, Marcel Pourbaix developed the Pourbaix diagram which describes a metal’s
reaction to an environment dependent on pH and voltage conditions. It describes when a metal
remains passive (non-corroding) and in which conditions metals become soluble (corrode). Steels are
passive in pH over 12 such as the condition when it is encased in cement. If the cement were to
carbonate and its pH reduce to below 12, the cement would no longer be able to act as a corrosion
inhibitor and the steel will begin to corrode when moist.
Some metals such as aluminum are amphoteric, meaning that they react with acids and bases. They
can corrode in low pH and in high pH conditions. Aluminum alloys are generally passive within a
pH of 4 and 8.5 but will corrode outside of those ranges. This is why aluminum cannot be embedded
in cement and why brick mortar should not be laid against an aluminum window frame without a
protective barrier between them.
5.2 Galvanic Series – In regards to dissimilar metal connections
All metals have a natural electrical potential. This electrical potential is measured using a high
impedance voltmeter connected to the metal being tested and with the common lead connected to a
copper copper-sulfate reference electrode (CSE) in water or soil. There are many types of reference
electrodes. In laboratory measurements, a Standard Hydrogen Electrode (SHE) is commonly used.
When different metal alloys are tested they can be ranked into an order from most noble (less
corrosion), to least noble (more active corrosion). When a more noble metal is connected to a less
noble metal, the less noble metal will become an anode and sacrifice itself through corrosion
providing corrosion protection to the more noble metal. This hierarchy is known as the galvanic
series named after Luigi Galvani whose experiments with electricity and muscles led Alessandro
Volta to discover the reactions between dissimilar metals leading to the early battery. The greater the
voltage difference between two metals, the faster the corrosion rate will be.
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 24
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
Table 1- Dissimilar Metal Corrosion Risk
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 25
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
Figure 5 - Galvanic series of metals relative to CSE half cell.
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 26
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
5.3 Corrosion Cell
In order for corrosion to occur, four factors must be
present. (1) The anode (2) the cathode (3) the
electrolyte and (4) the metallic or conductive path
joining the anode and the cathode. If any one of
these is removed, corrosion activity will stop. This
is how a simple battery produces electricity. An
example of a non-metallic yet conductive material is
graphite. Graphite is similar in nobility to gold. Do
not connect graphite to anything in moist
environments.
The anode is where the corrosion occurs, and the
cathode is the corrosion free material. Sometimes
the anode and cathode are different materials
connected by a wire or union. Sometimes the anode
and cathode are on the same pipe with one area of
the pipe in a low oxygen zone while the other part
of the pipe is in a high oxygen zone. A good
example of this is a post in the ocean that is
repeatedly splashed. Deep underwater, corrosion is
minimal, but at the splash zone, the corrosion rate is
greatest.
Low oxygen zones and crevices can also harbor
corrosive bacteria which in moist environments will
lead to corrosion. This is why pipes are laid on
backfill instead of directly on native cut soil in a
trench. Filling a trench slightly with backfill before
installing pipe then finishing the backfill creates a
uniform environment around the entire surface of
the pipe.
The electrolyte is generally water, seawater, or moist soil which allows for the transfer of ions and
electrical current. Pure water itself is not very conductive. It is when salts and minerals dissolve into
pure water that it becomes a good conductor of electricity and chemical reactions. Metal ores are
turned into metal alloys which we use in construction. They naturally want to return to their natural
metal ore state but it requires energy to return to it. The corrosion cell, creates the energy needed to
return a metal to its natural ore state.
The metallic or conductive path can be a wire or coupling. Examples are steel threaded into a copper
joint, or an electrician grounding equipment to steel pipes inadvertently connecting electrical grid
copper grounding systems to steel or iron underground pipes.
The ratio of surface area between the anode and the cathode is very important. If the anode is very
large, and the cathode is very small, then the corrosion rate will be very small and the anode may live
a long life. An example of this is when short copper laterals were connected to a large and long steel
pipeline. The steel had plenty of surface area to spread the copper’s attack, thus corrosion was not
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 27
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
noticeable. But if the copper was the large pipe and the steel the short laterals, the steel would
corrode at an amazing rate.
5.4 Design Considerations to Avoid Corrosion
The following recommendations are based upon typical observations and conclusions made by
forensic engineers in construction defect lawsuits and NACE International (Corrosion Society)
recommendations.
5.4.1 Testing Soil Factors (Resistivity, pH, REDOX, SO, CL, NO3, NH3)
As previously mentioned, different factors can cause corrosion. The most useful and common test for
categorizing a soil’s corrosivity has been the measure of soil resistivity which is typically measured in
units of (ohm-cm) by corrosion engineers and geologists. Soil resistivity is the ability of soil to
conduct or resist electrical currents and ion transfer. The lower the soil resistivity, the more
conductive and corrosive it is. The following are “generally” accepted categories but keep in mind,
the question is not “Is my soil corrosive?”, the question should be, “What is my soil corrosive to?”
and to answer that question, soil resistivity and chemistry must be tested. Though soil resistivity is a
good corrosivity indicator for steel materials, high chlorides or other corrosive elements do not
always lower soil resistivity, thus if you don’t test for chlorides and other water soluble salts,
you can get an unpleasant surprise. The largest contributing factor to a soil’s electrical resistivity
is its clay, mineral, metal, or sand make-up.
Table 2 - Corrosion Basics- An Introduction, NACE, 1984, pg 191
(Ohm-cm) Corrosivity Description
0-500 Very Corrosive
500-1,000 Corrosive
1,000-2,000 Moderately Corrosive
2,000-10,000 Mildly Corrosive
Above 10,000 Progressively less
corrosive
Testing a soil’s pH provides information to reference the Pourbaix diagram of specific metals. Some
elements such as ammonia and nitrates can create localized alkaline conditions which will greatly
affect amphoteric materials such as aluminum and copper alloys.
Excess sulfates can break-down the structural integrity of cement and high concentrations of
chlorides can overcome cement’s corrosion inhibiting effect on encased ferrous metals and break
down protective passivated surface layers on stainless steels and aluminum.
Corrosive bacteria are everywhere but can multiply significantly in anaerobic conditions with
plentiful sulfates. The bacteria themselves do not eat the metal but their by-products can form
corrosive sulfuric acids. The probability of corrosive bacteria is tested by measuring a soil’s
oxidation-reduction (REDOX) electro-potential and by testing for the presence of sulfides.
Only by testing a soil’s chemistry for minimum resistivity, pH, chlorides, sulfates, sulfides, ammonia,
nitrate, and redox potential can one have the information to evaluate the corrosion risk to construction
materials such as steel, stainless steel, galvanized steel, iron, copper, brass, aluminum, and concrete.
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 28
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
5.4.2 Proper Drainage
It cannot be emphasized enough that pooled stagnant water on metals will eventually lead to
corrosion. This stands for internal corrosion and external corrosion situations. In soils, providing
good drainage will lower soil moisture content reducing corrosion rates. Attention to properly sealing
polyethylene wraps around valves and piping will avoid water intrusion which would allow water to
pool against metals. Above ground structures should not have cupped or flat surfaces that will pond
water after rain or irrigation events.
Buildings typically are built on pads and have swales when constructed to drain water away from
buildings directing it towards an acceptable exit point such as a driveway where it continues draining
to a local storm drain. Many homeowners, landscapers and flatwork contractors appear to not be
aware of this and destroy swales during remodeling. The majority of garage floor and finished grade
elevations are governed by drainage during design.
17F
18,
18F
19
5.4.3 Avoiding Crevices
Crevices are excellent locations for oxygen differential induced corrosion cells to begin. Crevices
can also harbor corrosive bacteria even in the most chemically treated waters. Crevices will also
gather salts. If water’s total alkalinity is low, its ability to maintain a stable pH can also become more
difficult within a crevice allowing the pH to drop to acidic levels continuing a pitting process. Welds
in extremely corrosive environments should be complete and well filleted without sharp edges to
avoid crevices. Sharp edges should be avoided to allow uniform coating of protective epoxy.
Detection of crevices in welds should be treated immediately. If pressures and loads are low, sanding
and rewelding or epoxy patching can be suitable repairs. Damaged coatings can usually be repaired
with Direct to Metal paints. Scratches and crevice corrosion are like infections, they should not
be left to fester or the infection will spread making things worse.
18 https://www.fencedaddy.com/blogs/tips-and-tricks/132606467-how-to-repair-a-broken-fence-post
19 http://southdownstudio.co.uk/problme-drainage-maison.html
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 29
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
BAD GOOD
Figure 6- Defects which form weld crevices19F
20
5.4.4 Coatings and Cathodic Protection
When faced with a corrosive environment, the best defense against corrosion is removing the
electrolyte from the corrosion cell by applying coatings to separate the metal from the soil. During
construction and installation, there is always some scratch or damage made to a coating. NACE
training recommends that coatings be used as a first line of defense and that sacrificial or impressed
current cathodic protection is used as a 2nd line of defense to protect the scratched areas. Use of a
good coating dramatically reduces the amount of anodes a CP system would need. If CP is not
installed as a 2nd line of defense in an extremely corrosive environment, the small scratched zones
will suffer accelerated corrosion. CP details such as anode installation instructions must be designed
by corrosion engineers or vessel manufacturers on a per project basis because it depends on
electrolyte resistivity, surface area of infrastructure to be protected, and system geometry.
There are two types of cathodic protection systems, a Galvanic Anode Cathodic Protection (GACP)
system and an Impressed Current Cathodic Protection (ICCP) system. A Galvanic Anode Cathodic
Protection (GACP) system is simpler to install and maintain than an Impressed Current Cathodic
Protection (ICCP) system. To protect the metals, they must all be electrically continuous to each
other. In a GACP system, sacrificial zinc or magnesium anodes are then buried at locations per the
CP design and connected by wire to a structure at various points in system. At the connection points,
a wire connecting to the structure and the wire from the anode are joined in a Cathodic Protection
Test Station hand hole which looks similar in size and shape to an irrigation valve pull box. By
coating the underground structures, one can reduce the number of anodes needed to provide cathodic
protection by 80% in many instances.
An ICCP system requires a power source, a rectifier, significantly more trenching, and more
expensive type anodes. These systems are typically specified when bare metal is requiring protection
20 http://www.daroproducts.co.uk/makes-good-weld/
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 30
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
in severely corrosive environments in which galvanic anodes do not provide enough power to
polarize infrastructure to -850 mV structure-to-soil potential or be able to create a 100 mV potential
shift as required by NACE SP169 to control corrosion. In severely corrosive environments, a GACP
system simply may not last a required lifetime due to the high rate of consumption of the sacrificial
anodes. ICCP system rectifiers must be inspected and adjusted quarterly or at a minimum bi-annually
per NACE recommendations. Different anode installations may be possible but for large sites,
anodes are placed evenly throughout the site and all anode wires must be trenched to the rectifier.
For a large site, it may be beneficial to use two or more rectifiers to reduce wire lengths or trenching.
To simplify, a GACP system can be installed and practically forgotten with minor trenching because
the anodes can be installed very close to the structures. An ICCP system must be inspected annually
and anode wires run back to the rectifier which itself connects to the pile system. If any type of
trenching or development is expected to occur at the site during the life of the site, it is a good idea to
inspect the anode connections once a year to make sure wires are not cut and that the infrastructure is
still being provided adequate protection. A common situation that occurs with ICCP systems is that
a contractor accidently cuts the wires during construction then reconnects them incorrectly, turning
the once cathode, into a sacrificing anode.
Design of a cathodic protection system protecting against soil side corrosion requires that Wenner
Four Pin ground resistance measurements per ASTM G57 be performed by corrosion engineers at
various locations of the site to determine the best depths and locations for anode installations.
Ideally, a sample pile is installed and experiments determining current requirement are conducted.
Using this data, the decision is made whether a GACP system is feasible or if an ICCP must be used.
Figure 7- Sample anode design for fire hydrant underground piping
Vessels such as water tanks will have protective interior coatings and anodes to protect the interior
surfaces. Anodes can also be buried on site and connected to system skid supports to protect the
metal in contact with soil. A good example of a vessel cathodic protection system exists in all home
water heaters which contain sacrificial aluminum or magnesium anodes. In environments that exceed
140F, zinc anodes cannot be used with carbon steel because they become the aggressor (Cathodic) to
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 31
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
the steel instead of sacrificial (anodic). Anodes in vessels containing extremely brackish water with
chloride levels over 2,000 ppm should inspect or change out their anodes every 6 months.
Figure 8- Cross section of boiler with anode
Cathodic protection can only protect a few diameters within a pipeline thus it is not recommended for
small diameter pipelines and tubing internal corrosion protection. Anodes are like a lamp shining
light in a room. They can only protect along their line of sight.
5.4.5 Good Electrical Continuity
In order for cathodic protection to protect a long pipeline or system of pipes from external soil side
corrosion, they must all be electrically continuous to each other so that the electric current from the
anode can travel along the pipes, then return through the earth to the anode. Electrical continuity is
achieved by welding or pin brazing #8 AWG copper strand bond cable to the end of pipe sticks which
have rubber gaskets at bell and spigots. If steel pipes are joined by full weld, bonding wires are not
needed.
Electrical continuity between dissimilar metals is not desirable. Isolation joints or di-electric
unions should be installed between dissimilar metals, such as steel pipes connecting to a brass
valve per NACE SP0286. Bonding wires should then be welded onto the steel pipes by-passing the
brass valve so that the cathodic protection system’s current can continue to travel along the steel
piping but isolate the brass valve from the steel pipeline. Another option would be to provide a
separate cathodic protection system for steel pipes on both sides of the brass valve.
Typically, water heater inlets and outlets, gas meters and water meters have dielectric unions installed
in them to separate utility property from homeowner property. This also protects them in the case
that a home owner somehow electrically connects water pipes or gas pipes to a neighborhood
electrical grounding system which can potentially have less noble steel in soil now connected to much
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 32
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
more noble copper in soil which will then create a corrosion cell. This is exactly how a lemon
powered clock works when a galvanized zinc nail and a steel nail are inserted into a lemon then
connected to a clock. The clock is powered by the corrosion cell created.
5.4.6 Bad Electrical Continuity
Bad electrical continuity is when two different materials or systems are made electrically continuous
(aka shorted) when they were not designed to be electrically continuous. Examples of this would be
when gas lines are shorted to water lines or to electrical grounding beds. Very often, fire risers are
shorted to electrical grounding systems, and water pipes at business parks. Since fire risers usually
have a very short ductile iron pipe in the ground which connects to PVC pipe systems, they tend to
experience leaks after 7 to 10 years of being attacked by underground copper systems.
It is absolutely imperative that any copper water piping or other metal conduits penetrating cement
slab or footings, not come in contact with the reinforcing steel or post-tensioning tendons to avoid
creation of galvanic corrosion cells.
5.4.7 Corrosion Test Stations
Corrosion test stations should be installed every 1,000 feet along pipelines in order to measure
corrosion activity in the future. For a simple pipeline, two #8 AWG copper strand bond cable welded
or pin brazed onto the pipeline are run up to finished grade and left in a hand hole. Corrosion test
stations are used to measure pipe-to-soil electro potential relative to a copper copper-sulfate reference
electrode to determine if the pipe is experiencing significant corrosion activity. By measuring test
stations along a pipeline, hot spots can be determined, if any. The wires also allow for electrical
continuity testing, condition assessment, and a multitude of other types of tests.
At isolation joints and pipe casings, two wires should be welded to either side of the isolation joint for
a total of 4 wires to be brought up to the hand hole. This allows for future tests of the isolation joint,
casing separation confirmation, and pipe-to-soil potential readings during corrosion surveys.
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 33
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
Figure 9- Sample of corrosion test station specification drawing
5.4.8 Excess Flux in Plumbing
Investigations of internal corrosion of domestic water plumbing systems almost always finds excess
flux to be the cause of internal pitting of copper pipes. Some people believe that there is no such
thing as too much flux. Flux runs have been observed to travel up to 20 feet with pitting occurring
along the flux run. Flushing a soldered plumbing system with hot water for 15 minutes can remove
significant amounts of excess flux left in the pipes. If a plumbing system is expected to be stagnant
for some time, it should be drained to avoid stagnant water conditions that can lead to pitting and
dezincification of yellow brasses.
5.4.9 Landscapers and Irrigation Sprinkler Systems
A significant amount of corrosion of fences is due to landscaper tools scratching fence coatings and
irrigation sprinklers spraying these damaged fences. Recycled water typically has a higher salt
content than potable drinking water, meaning that it is more corrosive than regular tap water. The
same risk from damage and water spray exists for above ground pipe valves and backflow preventers.
Fiber glass covers, cages, and cement footings have worked well to keep tools at an arm’s length.
5.4.10 Roof Drainage splash zones
Unbelievably, even the location where your roof drain splashes down can matter. We have seen
drainage from a home’s roof valley fall directly down onto a gas meter causing it’s piping to corrode
at an accelerated rate reaching 50% wall thickness within 4 years. It is the same effect as a splash
Project X REPORT S220718Z 7/25/2022
Corrosion Engineering Page 34
Corrosion Control – Soil & Forensics Lab
29990 Technology Dr, Suite 13, Murrieta, CA 92563 Tel: 213-928-7213 Fax: 951-226-1720
www.projectxcorrosion.com
zone in the ocean or in a pool which has a lot of oxygen and agitation that can remove material as it
corrodes.
5.4.11 Stray Current Sources
Stray currents which cause material loss when jumping off of metals may originate from direct-
current distribution lines, substations, or street railway systems, etc., and flow into a pipe system or
other steel structure. Alternating currents may occasionally cause corrosion. The corrosion resulting
from stray currents (external sources) is similar to that from galvanic cells (which generate their own
current) but different remedial measures may be indicated. In the electrolyte and at the metal-
electrolyte interfaces, chemical and electrical reactions occur and are the same as those in the
galvanic cell; specifically, the corroding metal is again considered to be the anode from which current
leaves to flow to the cathode. Soil and water characteristics affect the corrosion rate in the same
manner as with galvanic-type corrosion.
However, stray current strengths may be much higher than those produced by galvanic cells and, as a
consequence, corrosion may be much more rapid. Another difference between galvanic-type currents
and stray currents is that the latter are more likely to operate over long distances since the anode and
cathode are more likely to be remotely separated from one another. Seeking the path of least
resistance, the stray current from a foreign installation may travel along a pipeline causing severe
corrosion where it leaves the line. Knowing when stray currents are present becomes highly important
when remedial measures are undertaken since a simple sacrificial anode system is likely to be
ineffectual in preventing corrosion under such circumstances.20F
21 Stray currents can be avoided by
installing proper electrical shielding, installation of isolation joints, or installation of sacrificial jump
off anodes at crossings near protected structures such as metal gas pipelines or electrical feeders.
Figure 10- Examples of Stray Current21F
22
21 http://corrosion-doctors.org/StrayCurrent/Introduction.htm
22 http://www.eastcomassoc.com/
Ki Project X
Corrosion Engineering
Lab Request Sheet Chaia of Custody
Phone: (213) 928-7213 - Fax (951) 226-1720 wvvw.projectxcorrosion.com
Ship Samples To: 29990 Technology Dr, Suite 13, Murrieta, CA 92563
Project X Job Neonbcr
IMPORTANT: Please complete Project aod Sample IdenttficatioB Data as you would like it to appear In report & include this form with samples.
Company Name:a/f'e rice-'Contact Name:PhooeNo: \ ^{fj
MailliiE Addnst:Contact Email:^vacgQ .coy>}
Accounting Contact:Invoice Email:
1 /
CHmt Project No:Project Name:paid
P.O.#:
5-Sl>^
Standard
3Day
Gaarantce
24 Hour
RUSH METHOD ANALYSIS REQUESTED (Please circle)
(Business Days) Turn Around Time:II 9 **i 1
Sg
1 =
B. 2
1:::
3S0 gSample' 'R :qcMin, 3Samples,tis emap, dna groundwater info
1
3
2
<
I,5(H> gSample
5?
For Corrosion Control Recommendations r350s soil sample):
S *
o
£*
z
-s
3^i
X s
S3 iNEED (I) Groundwater depth and: 1
{Z} 90II dampte i^ocaiions iviap
FOR THERMAL RESISTIVITY PROVIDE (l^OOg so 1 sample):
Dcfaidt
Method <c
3-s f.
^2 ^2
S|
53 H
3 F:
< 2
5"
5a
a 3K
52
25
55
25
52
25
52
2R
^2
5 £
52 < s
3i3|2s
5S u .*1
i-i ||
(1) Optimal Moisture %
Geo Quad
Redox Potential g
II c
4>
•a
c:
3
CO
Ammonia ^
ros
u
g
2
Flouride b Ph etahpso%
ries
E
a
5
Jj
E
s
1
CO
Potassium Magnesium
E
3
03
u
Ful lCorrosion Series
Kep
c
f 1
.> OS
O S
t -2
O §
it: «
o >
CO UJ
Water Corrosivity iM inReport ®Moisture Content Total klAilanity SoilRemolding hTlamreResistivit>'CNA() klANeiitr Cap )BRS(Sulfate Reducini Puckorius Index FRXEl iatnemeAnalys Water Hardness
(3) Desired Compaction
Date & Received By:
i i
>
<G
0^
'S a:
c.
s
3
C/5
Chloride
SAMPLE ID - BORE # - Description DEPTH (ft)DATE
cou-Enro
1 H/-]- I Q 1 /7/uA''^
-(^ Y y r
J Y/f-7 (2 !/
tiA-i re Y y •<
5 /\
b Y
1 /V
' 8 Y <
9 HA-sa-t 1
10 H/l -S e V y <
II HA-6G //
V y 4
13
14
15