ASTM G158-23

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Designation: G158 − 98 (Reapproved 2021) G158 − 23
Standard Guide for
Three Methods of Assessing Buried Steel Tanks
This standard is issued under the fixed designation G158; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
The purpose of this guide is to provide three methods of inspecting and assessing buried steel
tank(s) for corrosion damage and determining the suitability of these tanks prior to application of
cathodic protection.
1. Scope
1.1 This guide covers procedures to be implemented prior to the application of cathodic protection for evaluating the suitability
of a tank for upgrading by cathodic protection alone.
1.2 Three procedures are described and identified as Methods A, B, and C.
1.2.1 Method A—Noninvasive with primary emphasis on statistical and electrochemical analysis of external site environment
corrosion data.
1.2.2 Method B—Invasive ultrasonic thickness testing with external corrosion evaluation.
1.2.3 Method C—Invasive permanently recorded visual inspection and evaluation including external corrosion assessment.
1.3 This guide presents the methodology and the procedures utilizing site and tank specific data for determining a tank’s condition
and the suitability for such tanks to be upgraded with cathodic protection.
1.4 The tank’s condition shall be assessed using Method A, B, or C. Prior to assessing the tank, a preliminary site survey shall
be performed pursuant to Section 8 and the tank shall be tightness tested pursuant to 5.2 to establish that the tank is not leaking.
1.4 While this guide provides minimum procedures for assessing a tank’s condition, this guide does not provide minimum
installation procedures or requirements for upgrades of the tank by cathodic protection.
1.5 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only and are not considered standard.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
This guide is under the jurisdiction of ASTM Committee G01 on Corrosion of Metals and is the direct responsibility of Subcommittee G01.10 on Corrosion in Soils.
Current edition approved Aug. 1, 2021Dec. 1, 2023. Published August 2021January 2024. Originally approved in 1998. Last previous edition approved in 20162021 as
G158 – 98 (2016).(2021). DOI: 10.1520/G0158-98R21.10.1520/G0158-23.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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1.7 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 The most recent version of the following documents should be consulted as references by those using this guide:
2.2 ASTM Standards:
D2216 Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass
E114 Practice for Ultrasonic Pulse-Echo Straight-Beam Contact Testing
E797/E797M Practice for Measuring Thickness by Manual Ultrasonic Pulse-Echo Contact Method
E1323 Guide for Evaluating Laboratory Measurement Practices and the Statistical Analysis of the Resulting Data
E1526 Practice for Evaluating the Performance of Release Detection Systems for Underground Storage Tank Systems
(Withdrawn 2002)
G51 Test Method for Measuring pH of Soil for Use in Corrosion Evaluations
G57 Test Method for Measurement of Soil Resistivity Using the Wenner Four-Electrode Method
G193 Terminology and Acronyms Relating to Corrosion
2.3 ASNT Standard:
ASNT SNT-TC-1A Personnel Qualification and Certification in Nondestructive Testing
2.4 NACE InternationalAMPP (formerly NACE International) Standards:
RP-0169NACE SP0169 (formerly RP0169) Standard Recommended Practice-Control Practice – Control on External Corrosion
on Underground or Submerged Metallic Piping Systems
RP-0187NACE SP0187 (formerly RP0187) Standard Recommended Practice-Design Practice – Design Considerations for
Corrosion Control of Reinforcing Steel in Concrete
RP-0285NACE SP0285 (formerly RP0285) Standard Recommended Practice-Corrosion Practice – Corrosion Control of
Underground Storage Tank Systems by Cathodic Protection
2.5 Environmental Protection Agency Methods:
EPA SW 846 Test Methods for Evaluating Solid Waste
EPA 371.1 Measurement of Sulfate Reducing Bacteria
2.6 National Fire Protection Association (NFPA) Practice:
NFPA 329 Recommended Practice for Handling Underground Releases of Flammable and Combustible Liquids
2.7 Underwriters Laboratories Standard:
UL 58 Steel Underground Tanks for Flammable and Combustible Liquids
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 buried—buried, adj—to be placed in the ground and covered with earth.
3.1.2 cathodic protection—protection, n—an applied technique to prevent further corrosion of a metal surface by making that
surface the cathode of an electrochemical cell. For example, a tank system can be cathodically protected through the application
of either galvanic anodes or impressed current.
3.1.3 corrosion specialist/cathodic protection specialist—specialist, n—a competent person who by reason of knowledge of the
physical sciences and the principles of engineering and mathematics, acquired by education and related practical experience, is
qualified to engage in the practice of corrosion control on buried or submerged metallic piping systems and metallic tanks. Such
persons shall are recommended to be registered professional engineers or persons recognized as corrosion specialists or cathodic
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
Available from American Society for Nondestructive Testing (ASNT), P.O. Box 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org.
Available from NACE International (NACE), AMPP International, 15835 Park Ten Pl., Houston, TX 77084, http://www.nace.org.http://www.ampp.org.
Available from United States Environmental Protection Agency (EPA), Office of Underground Storage Tanks, William Jefferson Clinton Bldg., 1200 Pennsylvania Ave.,
NW, Washington, DC 20460, http://www.epa.gov.
Available from National Fire Protection Association (NFPA), 1 Batterymarch Park, Quincy, MA 02269-9101.
Available from Underwriters Laboratories (UL), UL Headquarters, 333 Pfingsten Road, Northbrook, IL, 60062, http://www.ul.com.
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protection specialists by NACE, NACE (AMPP), if their professional activities include suitable experiences in external corrosion
control on buried or submerged metallic piping and tanks.
3.1.4 corrosion technician—technician, n—a person possessing basic knowledge of corrosion and corrosion control, who is
capable of performing routine, well defined work under the supervision of the corrosion specialist/cathodic protection specialist.
3.1.5 invasive procedure—procedure, n—a method of determining the corrosion status of a tank by assessing the tank from the
inside as part of the upgrade procedure. Further, for the purposes of this guide, it does not require manned entry into the tank. (See
non-invasive.)
3.1.6 limitations—limitations, n—The user of this guide is encouraged to review any available third party verification information
provided as part of the vendor selection process.
3.1.7 noninvasive procedure—procedure, n—a method of determining the corrosion status of a tank from the characteristics of its
surroundings with minimal entry into the tank. Further, for the purposes of this guide, it does not require manned entry into the
tank. (See invasive.)
3.1.8 pH—the numerical value of the negative logarithm of the hydrogen ion concentration in moles per litre in an electrolyte.
3.1.9 redox potential—potential of platinized platinum electrode in a redox environment (reversible system). The value of redox
potential depends on whether the system is in the oxidized, partially oxidized, partially reduced, or reduced state.
3.1.8 tank tightness test—test, n—a method capable of detecting a 0.1 gal/h leak rate, while accounting for any applicable effects
of thermal expansion or contraction of the product, of vapor pockets, of tank deformation, of evaporation or condensation, and of
the location of the water table. The method mustshould be capable of detecting a 0.1 gal/h leak rate with a probability of detection
of at least 0.95 and a probability of false alarm of at most 0.05 or in accordance with NFPA 329.
3.1.9 unconditional probability of corrosion failure—failure, n—the probability of corrosion failure which includes a determina-
tion of whether localized, pitting, or general corrosion is occurring.
3.1.10 underground storage tank (UST)—(UST), n—any one or combination of tanks (including connected underground piping),
the volume of which is 10 % or more beneath the surface of the ground.
3.1.11 upgrade—upgrade, n—the addition to or retrofit of UST systems using approaches including, but not limited to, cathodic
protection to improve the ability of a UST system to prevent a release.
3.1.12 UST—UST, n—see underground storage tank (see 3.1.123.1.10).
3.1.13 vendor provided information—information, n—The user is referred to Annex A1 for a specific form and format of
information which mustshould be provided by a vendor. This information consists of historic performance data on a method and
is mandatedrecommended as part of the guide.
4. Significance and Use
4.1 This guide provides three methods for determining the suitability of a buried steel tank to be upgraded with cathodic
protection.
4.2 This guide may be used to assess any UST, including non-regulated USTs.
4.3 This guide provides three alternative methods but does not recommend any specific method or application. The responsibility
for selection of a method rests with the user.
4.4 This guide has specific requirementssuggestions for vendor provided information which should be requested and reviewed by
the user.
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5. Permits, Plans and Tank Leak Testing
5.1 Prior to engaging in any activities relating to the alteration, repair, or upgrade of any UST system, consult all necessary
authorities should be consulted to obtain any required permits.
5.2 Tank Leak Testing:
5.2.1 To establish that tanks are not leaking prior to assessment, they shallshould be assessed by a leak detection system. This leak
detection assessment alone is not sufficient to determine that a tank is suitable for upgrading with cathodic protection under this
guide.
5.2.2 A tightness test or another release detection system in accordance with NFPA 329 shallshould be used. Any release detection
mustshould be capable of detecting a leak from any portion of the tank that routinely contains product, and be independently
evaluated and certified in accordance with Practice E1526 or the equivalent. Leak detection results shallshould be provided to the
corrosion specialist/cathodic protection specialist.
5.2.3 This testing shall is recommended to be accomplished within six months prior to performing any of the assessment
procedures.
6. Required Approvals and Certifications
6.1 The corrosion assessment work carried out under this guide shallshould be performed under the responsible direction of a
corrosion specialist/cathodic protection specialist as defined in 3.1.3.
6.2 The corrosion specialist/cathodic protection specialist shallshould certify to the tank owner or operator that the personnel
performing the assessment work on the tank are knowledgeable of all the applicable procedures in this guide.
6.3 The corrosion specialist/cathodic protection specialist shallshould certify to the tank owner or operator that all work was
performed in strict accordance with this guide.
7. General Safety Requirements
7.1 All personnel shallshould comply with applicable federal, state, and local health and safety codes and regulations.
8. Preliminary Site Survey
8.1 A corrosion technician, under the responsible direction of the corrosion specialist/cathodic protection specialist, shallshould
obtain tank site specific information as appropriate to the method of assessment to be used.
8.1.1 Facility Information:
8.1.1.1 Address or location, and
8.1.1.2 Name and telephone number of owner and operator contact personnel.
8.1.2 Tank and Piping Details:
8.1.2.1 Number and capacity,
8.1.2.2 Location and dimensions,
8.1.2.3 Age,
8.1.2.4 Material of construction,
8.1.2.5 Electrical isolation,
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8.1.2.6 Type of product stored,
8.1.2.7 Names of site contact personnel,
8.1.2.8 Backfill material,
8.1.2.9 Coatings and linings,
8.1.2.10 Leak history,
8.1.2.11 Repair history,
8.1.2.12 Site plans,
8.1.2.13 Installation specifications,
8.1.2.14 Tank excavation liners, and
8.1.2.15 As-built drawings.
8.1.3 Information Not in the Immediate Vicinity of the Tanks—The presence of the following items, that are external to the tank
area, shallshould be investigated and included as appropriate to the method of assessment of the suitability of tanks for upgrading
with cathodic protection:
8.1.3.1 Stray dc current sources,
8.1.3.2 Existing cathodic protection systems,
8.1.3.3 Steel product and vent piping and fittings, and
8.1.3.4 Adjacent subsurface metallic/steel-reinforced concrete structures.
8.2 Preliminary Evaluation—Prior to assessing the tank, a preliminary site survey mustshould be performed pursuant to Section
8 and a tightness test must be performed pursuant to 5.2 to establish that the tank is not leaking.
9. Method A—Noninvasive with Primary Emphasis on Statistical and Electrochemical Analysis of External Site
9, 10
Environment Corrosion Data(1, 2)
9.1 Field and Laboratory Testing—Noninvasive with Primary Emphasis on Statistical and Electrochemical Analysis of External
Site Environment Corrosion Data.
9.1.1 Tests shall are recommended to be conducted by, or as directed by a corrosion specialist/cathodic protection specialist.
9.1.2 Field Testing Procedures—Tests to be performed shallshould include, but are not limited to, the following:
9.1.2.1 Stray Currents—Perform tests to detect the presence of stray currents at each tank site. This test shall is recommended to
consist of measuring structure-to-soil potentials at right angles at a minimum of two locations within the tank facilities and
observing the measurements for not less than 2 h 2 h at a time when such influences are most likely to occur. The monitor
shallshould consist of a field data acquisition unit, with a minimum of 10 MΩ input impedance, used in conjunction with a stable
reference cell(s) placed in contact with the soil in the vicinity of the tank. The instrument shall is recommended to measure and
store structure-to-electrolyte potential (voltage) data at least every 5 s 5 s throughout the entire duration of field investigation at
the site or for 2 h, 2 h, whichever is greater. If variations of 650 mV 650 mV or greater are measured during the test period, make
24 h recording measurements are recommended to confirm stray current effects.
Bushman, J., B. and Mehalick, T., E. “Statistical Analysis of Soil Characteristics to Predict Mean Time to Corrosion Failure of Underground Metallic Structures,” ASTM
STP 1013, ASTM, 1989.
Rogers, W., F. “Statistical Prediction of Corrosion Failures,” NACE International, CORROSION 89, Paper No. 596.
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9.1.2.2 Tank Information:
(a) Locate all tanks and confirm materials of construction, age, capacity, and dimensions. Produce detailed site sketches
describing the layout of the UST system and above grade pertinent details for each site.
(b) Determine the presence and extent of internal corrosion immediately below the fill riser. If the depth of corrosion
penetration in the tank shell exceeds 50 % of the tank wall thickness, the UST shall is recommended to be declared to have failed
the test and the procedure.
(c) Determine if the tanks and piping are electrically continuous.
9.1.2.3 Bore Hole Tests:
(a) Determine locations for soil borings in the field. Make two test holes for each tank excavation zone with four or fewer tanks.
For tank excavation zones with more than four tanks, make one additional bore hole for each two additional tanks, or part thereof.
Make the tank bore holes at opposite diagonal ends of the tank excavation zone. The tank excavation zone shall be considered is
recommended to extend no farther than 4 ft from the nearest tank. Complete the holes to the bottom of the deepest tank.
(b) In each tank bore hole, record measurements as the boring progresses. At 2 ft (0.6 m) intervals, make the following
tests:tests are recommended:
(1) Measure the soil resistivity using the Wenner four pin method in accordance with Test Method G57.
(2) Make structure-to-soil potential measurements in each bore hole using a minimum 10 MΩ input impedance digital
voltmeter and a calibrated copper-copper sulfate reference electrode sensing tip in direct contact with the soil in the bore hole.
(c) Measure the depth of observed, perched, or static water table in each bore hole, if encountered.
(d) In accordance with industry practices, gather one soil sample each at the top, mid depth, and bottom of each hole using
either a split spoon or core sampling tube and place, seal, and preserve the soil samples in containers for laboratory analysis.
(e) Backfill each hole and seal with a concrete or asphalt plug.
9.1.2.4 Other Field Considerations—The corrosion specialist/cathodic protection specialist may also consider, but not be limited
to, consider performing and evaluating the following tests:
(a) Current requirement,
(b) Coating resistance, and
(c) Coating efficiency.
9.1.3 Laboratory Testing Procedures—Send It is recommended to send soil samples collected at each site to a qualified soil
laboratory where they shallcan be tested in accordance with EPA SW 846 Guide E1323, or other recognized industry test methods.
The report shallshould include the results of all test methods used in the evaluation. At a minimum, obtain the following data:the
following data are recommended to be obtained:
9.1.3.1 Soil resistivity/conductivity,
9.1.3.2 Moisture content,
9.1.3.3 Soil pH,
9.1.3.4 Soluble chloride ion concentration, and
9.1.3.5 Sulfide ion concentration.
9.1.4 The corrosion specialist/cathodic protection specialist shallshould also consider, but not be limited to, performing and
evaluating the following tests. The report shallshould include all test methods used in the evaluation:
9.1.4.1 Redox potential, and
9.1.4.2 Sulfate ion concentration.concentration, and
9.1.4.3 Any other tests required by the external corrosion rate analysis model.
9.1.5 Quality Control—One soil sample of every ten samples analyzed shall is recommended to be subjected to an independent
quality control analysis of all data gathered in 9.1.3. If the results of the quality control analysis fail to agree with the original
analysis (within limits of experimental accuracy), reanalyze all samples collected since the last successful quality control analysis.
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9.2 Analysis and Determination of Suitability of a Tank for Upgrading with Cathodic Protection-Noninvasive with Primary
Emphasis on Statistical Analysis of External Site Environment Corrosion Data.Data:
9.2.1 Basis for Analysis—By examining the environment in the specific vicinity of the tank, a relationship between the
aggressiveness of the environment and the rate of corrosion can be statistically established. Base the statistical analysis model used
on a sufficient size data base with various factors that are accounted for statistically to reach a confidence level of 0.99. This will
achieve consistency and reliability of the results. One general form of the multivariate, non-linear regression analysis, which
contains the minimum essential variables, is as follows:
E Age 5 f R,M,Cl,pH,S,SC,TS,P (1)
~ ! ~ !
where:
E (Age) = unconditional predicted age to corrosion failure,
R = resistivity,
M = moisture content,
Cl = chloride ion concentration,
pH = soil pH,
S = sulfide ion concentration,
SC = stray current magnitude,
TS = tank size, and
P = tank structure to soil potential.
9.2.2 Criteria of Acceptance for Upgrading With Cathodic Protection (using RP-0169, RP-0187, and RP-0285)SP0169, SP0187,
and SP0285)—To be acceptable as a means of determining the condition of tanks and their suitability for upgrading with cathodic
protection, the procedure used shall,should, at a minimum, meet the following criteria:
9.2.2.1 The procedure shall be is based on an evaluation of all data gathered in situ in each bore hole together with all soil sample
data and the stray dc earth current monitor measurements taken at each site.
9.2.2.2 The mathematical formulation of the procedure shall conform conforms to accepted physical and electrochemical
characteristics of the tank corrosion process. Independent professional validation of these processes shall be doneis recommended
to be conducted by an individual or individuals with experience in the relevant scientific or engineering disciplines.
9.2.2.3 Parameter estimates shall be are based on data derived from at least 100 sites where a minimum of 200 tanks were
excavated, fully exposed, and evaluated by a qualified corrosion specialist/cathodic protection specialist. Maximum likelihood
estimation or another procedure that meets the standards of statistical or electrochemical admissibility shallshould be required.
Data used in estimation shallshould contain representative samples of leaking and non-leaking tanks.
9.2.2.4 Models proposed shallshould be specific as to soil type and incorporate depth of ground water and rainfall experienced in
the immediate geographical area where testing takes place.
9.2.2.5 The standard deviation of the predicted time to corrosion failure shall is recommended to not exceed 1.5 years. The model
shallshould generate an unconditional probability of corrosion failure based upon a comparison of actual tank age to its expected
leak-free life.
9.2.3 Report Including Results, Analysis, and Recommendations—The corrosion specialist/cathodic protection specialist
shallshould prepare a report including results, analysis, and recommendations as follows:
9.2.3.1 Base the report conclusions on the expected leak-free life of a tank at a specific site as determined by the analysis of the
data necessary to determine which tanks are suitable for upgrading with cathodic protection.
9.2.3.2 The report shallshould provide the expected leak-free life and present and future probabilities of corrosion failure for all
tanks investigated.
9.2.3.3 The report shallshould include a listing of tanks whose age is less than the expected leak-free life and for those tanks where
the probability of corrosion perforation is less than 0.05.
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9.3 Cathodic protection can be applied to those tanks that have been tested in accordance with Sections 8 and 9 and meet the
following criteria:
9.3.1 The tank is confirmed to be leak free leak-free in accordance with 5.2.
9.3.2 The tank age is less than the expected leak-free life.
9.3.3 The probability of corrosion perforation of the tank is less than 0.05.
9.3.4 Either a tank tightness test is conducted between three and six months after the tank is cathodically protected, or monthly
monitoring with another leak detection system is should be implemented within one month after the addition of cathodic protection.
Any leak detection system must is recommended to meet 5.2.2.
9.4 A recommended form is included in Annex A1 which mustcan be utilized to report the results of the authenticated vendor
provided information. A research report containing examples of actual authenticated vendor provided information is filed and
available from ASTM.
10. Method B—Invasive Ultrasonic Thickness Testing with External Corrosion Evaluation
10.1 Field and Laboratory Testing—Invasive Ultrasonic Thickness Testing with External Corrosion Evaluation:
10.1.1 Conduct the The following procedures are recomm
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