ASTM G51-18

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: G51 − 95 (Reapproved 2012) G51 − 18
Standard Test Method for
1
Measuring pH of Soil for Use in Corrosion Testing
This standard is issued under the fixed designation G51; 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.
1. Scope
1.1 This test method covers a procedure for determining the pH of a soil in corrosion testing. The principle use of the test is
to supplement soil resistivity measurements and thereby identify conditions under which the corrosion of metals in soil may be
accentuated (see G57–78(1984)). – 78 (2012)).
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.4 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
2.1 ASTM Standards:
D1193 Specification for Reagent Water
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
G57 Test Method for Field Measurement of Soil Resistivity Using the Wenner Four-Electrode Method
NACE/ASTM G193 Terminology and Acronyms Relating to Corrosion
G215 Guide for Electrode Potential Measurement
3. Terminology
3.1 Definitions:
3.1.1 calibration solution, n—a commercially available solution with a stable pH used for calibrating a pH measuring system
(meter and probe).
3.1.2 calomel electrode, n—an electrode that develops a standard electric potential and is used to provide a reference voltage
in the circuit for sensing electrodes. It is composed of an amalgam of mercury and mercury (I) chloride.
3.1.2.1 Discussion—
Due to shipping restrictions on mercury containing materials, calomel electrodes have been replaced by silver/silver chloride
electrodes in newer pH meters.
3.1.3 combination electrode, n—an electrochemical apparatus that incorporates an ion-selective electrode and a reference
electrode in a single assembly thereby avoiding the need for a separate reference electrode.
+ +
3.1.4 pH, n—the negative logarithm of the hydrogen ion activity written as pH = –log (a ) where a = Hydrogen ion activity
10 H H
= the molar concentration of hydrogen ions multiplied by the mean ion-activity coefficient.
1
This test method 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 May 1, 2012Nov. 1, 2018. Published June 2012December 2018. Originally approved in 1977. Last previous edition approved in 20052012 as
G51–95(2005).G51 – 95(2012). DOI: 10.1520/G0051-95R12.10.1520/G0051-18.
2
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.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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G51 − 18
3.1.5 pH meter, n—an instrument with a display of pH units. For field use, it is portable and battery-powered.
3.1.6 purified water, n—water that meets Specification D1193, Type IV requirements.
3.1.7 silver/silver chloride electrode, n—an electrode that develops a standard electric potential and is used to provide a
reference voltage. The electrode functions as a redox electrode and the equilibrium is between the silver metal (Ag) and it salt –
Silver Chloride (AgCl).
3.1.7.1 Discussion—
Refer to detailed description and discussion in Guide G215.
3.2 The terminology used herein, if not specifically defined otherwise, shall be in accordance with NACE/ASTM G193.
Definitions provide
...

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: G51 − 18
Standard Test Method for
1
Measuring pH of Soil for Use in Corrosion Testing
This standard is issued under the fixed designation G51; 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.
1. Scope 3. Terminology
1.1 This test method covers a procedure for determining the 3.1 Definitions:
pH of a soil in corrosion testing. The principle use of the test
3.1.1 calibration solution, n—a commercially available so-
is to supplement soil resistivity measurements and thereby
lution with a stable pH used for calibrating a pH measuring
identify conditions under which the corrosion of metals in soil
system (meter and probe).
may be accentuated (see G57 – 78 (2012)).
3.1.2 calomel electrode, n—an electrode that develops a
1.2 The values stated in SI units are to be regarded as
standard electric potential and is used to provide a reference
standard. No other units of measurement are included in this
voltage in the circuit for sensing electrodes. It is composed of
standard.
an amalgam of mercury and mercury (I) chloride.
1.3 This standard does not purport to address all of the
3.1.2.1 Discussion—Due to shipping restrictions on mer-
safety concerns, if any, associated with its use. It is the
cury containing materials, calomel electrodes have been re-
responsibility of the user of this standard to establish appro-
placed by silver/silver chloride electrodes in newer pH meters.
priate safety, health, and environmental practices and deter-
3.1.3 combination electrode, n—an electrochemical appara-
mine the applicability of regulatory limitations prior to use.
tus that incorporates an ion-selective electrode and a reference
1.4 This international standard was developed in accor-
electrode in a single assembly thereby avoiding the need for a
dance with internationally recognized principles on standard-
separate reference electrode.
ization established in the Decision on Principles for the
3.1.4 pH, n—the negative logarithm of the hydrogen ion
Development of International Standards, Guides and Recom-
+ +
activity written as pH = –log (a ) where a = Hydrogen ion
mendations issued by the World Trade Organization Technical
10 H H
activity = the molar concentration of hydrogen ions multiplied
Barriers to Trade (TBT) Committee.
by the mean ion-activity coefficient.
2. Referenced Documents
3.1.5 pH meter, n—an instrument with a display of pH units.
2
2.1 ASTM Standards:
For field use, it is portable and battery-powered.
D1193 Specification for Reagent Water
3.1.6 purified water, n—water that meets Specification
E177 Practice for Use of the Terms Precision and Bias in
D1193, Type IV requirements.
ASTM Test Methods
3.1.7 silver/silver chloride electrode, n—an electrode that
E691 Practice for Conducting an Interlaboratory Study to
develops a standard electric potential and is used to provide a
Determine the Precision of a Test Method
reference voltage. The electrode functions as a redox electrode
G57 Test Method for Field Measurement of Soil Resistivity
and the equilibrium is between the silver metal (Ag) and it salt
Using the Wenner Four-Electrode Method
– Silver Chloride (AgCl).
NACE/ASTM G193 Terminology and Acronyms Relating to
Corrosion
3.1.7.1 Discussion—Refer to detailed description and dis-
G215 Guide for Electrode Potential Measurement cussion in Guide G215.
3.2 The terminology used herein, if not specifically defined
otherwise, shall be in accordance with NACE/ASTM G193.
1
This test method is under the jurisdiction of ASTM Committee G01 on
Definitions provided herein and not given in NACE/ASTM
Corrosion of Metals and is the direct responsibility of Subcommittee G01.10 on
G193 are limited only to this standard.
Corrosion in Soils.
Current edition approved Nov. 1, 2018. Published December 2018. Originally
approved in 1977. Last previous edition approved in 2012 as G51 – 95(2012). DOI:
4. Significance and Use
10.1520/G0051-18.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
4.1 Information on pH of soil is used as an aid in evaluating
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
the corrosivity of a soil environment. Some metals are more
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. sensitive to the pH of their environment than others, and
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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G51 − 18
information on the stability of a metal as a function of pH and mometers come in
...