ASTM G51-95(2005)

Standard Test Method for Measuring pH of Soil for Use in Corrosion Testing

SIGNIFICANCE AND USE
Information on pH of soil is used as an aid in evaluating the corrosivity of a soil environment. Some metals are more sensitive to the pH of their environment than others, and information on the stability of a metal as a function of pH and potential is available in the literature.3
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 G 57 - 78 (1984)).
1.2 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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 30-Sep-2005
• ICS: 13.080.10 - Chemical characteristics of soils
• Technical Committee: G01 - Corrosion of Metals
• Drafting Committee: G01.10 - Corrosion in Soils

Relations

• Replaces: ASTM G51-95(2000) - Standard Test Method for Measuring pH of Soil for Use in Corrosion Testing
• Effective Date: 01-Oct-2005
• Replaced By: ASTM G51-95(2012) - Standard Test Method for Measuring pH of Soil for Use in Corrosion Testing
• Effective Date: 01-May-2012
• Referred By: ASTM D4972-19 - Standard Test Methods for pH of Soils
• Effective Date: 01-Oct-2005
• Referred By: ASTM E2277-14(2019) - Standard Guide for Design and Construction of Coal Ash Structural Fills
• Effective Date: 01-Oct-2005
• Referred By: ASTM G200-20 - Standard Test Method for Measurement of Oxidation-Reduction Potential (ORP) of Soil
• Effective Date: 01-Oct-2005
• Referred By: ASTM G218-19 - Standard Guide for External Corrosion Protection of Ductile Iron Pipe Utilizing Polyethylene Encasement Supplemented by Cathodic Protection
• Effective Date: 01-Oct-2005
• Referred By: ASTM D2976-22a - Standard Test Method for pH of Peat Materials
• Effective Date: 01-Oct-2005
• Referred By: ASTM D7765-18a - Standard Practice for Use of Foundry Sand in Structural Fill and Embankments
• Effective Date: 01-Oct-2005
• Referred By: ASTM G162-18 - Standard Practice for Conducting and Evaluating Laboratory Corrosion Tests in Soils
• Effective Date: 01-Oct-2005
• Referred By: ASTM G158-98(2021) - Standard Guide for Three Methods of Assessing Buried Steel Tanks
• Effective Date: 01-Oct-2005
• Referred By: ASTM E2788/E2788M-18 - Standard Specification for Use of Expanded Shale, Clay and Slate (ESCS) as a Mineral Component in the Growing Media and the Drainage Layer for Vegetative (Green) Roof Systems
• Effective Date: 01-Oct-2005
• Referred By: ASTM D420-18 - Standard Guide for Site Characterization for Engineering Design and Construction Purposes
• Effective Date: 01-Oct-2005

Standards Content (Sample)

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:G51–95 (Reapproved 2005)
Standard Test Method for
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.Anumber in parentheses indicates the year of last reapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 4.2 Calomel and Glass Electrodes:
4.2.1 Use a saturated calomel reference electrode or its
1.1 This test method covers a procedure for determining the
equivalent in the pH determination. A few crystals of solid
pH of a soil in corrosion testing. The principle use of the test
potassium chloride should always be present within the cham-
is to supplement soil resistivity measurements and thereby
ber surrounding the calomel to assure that the solution is
identify conditions under which the corrosion of metals in soil
saturated under the conditions of use. The design of the
may be accentuated (see G57–78(1984)).
electrode must permit the formation of a fresh liquid junction
1.2 This standard does not purport to address all of the
between the solution of potassium chloride and the buffer or
safety concerns, if any, associated with its use. It is the
test soil for each test and allow traces of soil to be readily
responsibility of the user of this standard to establish appro-
removed by washing.
priate safety and health practices and determine the applica-
4.2.2 A glass electrode of rugged construction is required.
bility of regulatory limitations prior to use.
The performance of the glass electrode is satisfactory if it
2. Referenced Documents
furnishes the correct pH value (60.1 pH unit) for standard
buffered solutions.
2.1 ASTM Standards:
4.2.3 A combination electrode consisting of a saturated
E177 Practice for Use of the Terms Precision and Bias in
calomel reference electrode and a glass electrode (4.2.1 and
ASTM Test Methods
4.2.2) combined as a single electrode is acceptable. However,
E691 Practice for Conducting an Interlaboratory Study to
the requirements outlined above are equally applicable to the
Determine the Precision of a Test Method
electrodes used in this combination unit.
G57 Test Method for Field Measurement of Soil Resistivity
4.3 Subsurface Probe—When pH measurements below the
Using the Wenner Four-Electrode Method
surface of the soil are required, it is necessary to use a probe of
3. Significance and Use
suitable length which will allow measurements to be made at
the depth of interest.This probe consists of a glass electrode or
3.1 Information on pH of soil is used as an aid in evaluating
a combination electrode in a rubber housing at the end of a
the corrosivity of a soil environment. Some metals are more
plastic tube. One type of probe is illustrated in Fig. 1.
sensitive to the pH of their environment than others, and
4.4 Soil Thermometer—Some pH electrodes have tempera-
information on the stability of a metal as a function of pH and
ture compensation built in as part of the pH electrode, but most
potential is available in the literature.
do not (see manufacturers’ specifications). A thermometer of
4. Apparatus
rugged construction is required for soil use, and a stainless
steel sheathed thermometer is preferred. Metal sheathed ther-
4.1 pH Meters—A portable, battery-powered pH meter is
mometers come in different lengths, and a length appropriate
necessary for field measurements. Most instruments can also
for the depth of interest should be chosen.
function as a high-impedance voltmeter. An LCD display is
preferred for its readability in a bright, outdoor environment.
5. Reagents and Materials
5.1 During the calibration procedure for the pH meter,
This test method is under the jurisdiction of ASTM Committee G01 on
standard buffered solutions of known pH are necessary. These
Corrosion of Metals, and is the direct responsibility of Subcommittee G01.10 on
solutions, or tablets to make up these solutions, can be
Corrosion in Soils.
Current edition approved Oct. 1, 2005. Published October 2005. Originally
purchased from chemical supply companies or pH equipment
approved in 1977. Last previous edition approved in 2000 as G51 – 95 (2000). DOI:
manufacturers.
10.1520/G0051-95R05.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
6. Sampling
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
6.1 By the nature of the measurement, pH is determined for
the ASTM website.
a small volume of soil at each reading, and it is important that
Pourbaix, M., “Atlas of Electrochemical Equilibria in Aqueous Solutions,”
at least three measurements at different locations be made and
Pergamon Press, 1966.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
G51–95 (2005)
FIG. 1 Subsurface probe
a simple average calculated. The regions of interest, surface, 7.2.2 Immerse the electrodes in the known standard solution
subsurface, or both, where applicable, must be sampled. and calibrate the meter in accordance with the manufacturer’s
instructions.
7. Calibration and Standardization
8. Procedure
7.1 Test for Linearity—Prior to field use, or periodically
when used extensively in the field, test the apparatus for
8.1 Soil Preparation for pH Determination:
linearity of response. This procedure is as follows:
8.1.1 Ideally the pH measurement should be made in the
7.1.1 Turn on the instrument, allow to warm up thoroughly,
field with the glass electrode contacting the soil at the specific
and bring to electrical balance in accordance with the manu-
depth of interest. If the surface soil pH is desired, then the soil
facturer’sinstructions.Beforeuse,cleanandrinsetheglassand
can be broken up if compacted so as to accept the electrodes.
calomel electrodes in distilled water.
If a subsurface pH is desired, then a boring or an excavation
7.1.2 At least two standard buffered pH solutions that span
must be done so that the electrode can be placed in the soil at
the soil pH to be measured are required. From practical
the desired depth.The subsurface probe (Fig. 1) is ideal for use
experience standard solutions of pH 4, 7, and 8 are recom-
with a boring tool such as hand auger.After boring through the
mended. For the test, the temperature of these solutions shall
soil to the depth of interest, carefully lower the probe into the
not differ from each other by more than 5°C. A laboratory
cavity without further preparation of the soil.
thermometer can be used for these measurements.
8.1.2 Soil samples can be brought to the surface with a
7.1.3 Adjust the temperature compensating dial on the pH
boring tool or a post-hole digger, and the measurement made in
meter to the standard solution temperature.
the field on the soil thus obtained. This technique is less
7.1.4 Immerse the electrodes in a
...