ASTM D6547-23

Standard Test Method for Corrosiveness of Lubricating Fluid to Bimetallic Couple

SIGNIFICANCE AND USE
5.1 Corrosiveness of a fluid to a bimetallic couple is one of the properties used to evaluate hydraulic or lubricating fluids. It is an indicator of the compatibility of a fluid with a brass on steel galvanic couple at ambient temperature and 50 % relative humidity.
SCOPE
1.1 This test method covers the corrosiveness of hydraulic and lubricating fluids to a bimetallic galvanic couple.
Note 1: This test method replicates Fed-Std No. 791, Method 5322.2. It utilizes the same apparatus, test conditions, and evaluation criteria, but it describes test procedures more explicitly.  
1.2 The values stated in SI units are to be regarded as standard.  
1.2.1 Exception—The values given in parentheses are for information only.  
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, health, and environmental 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.

General Information

• Status: Published
• Publication Date: 14-Dec-2023
• ICS: 75.120 - Hydraulic fluids
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.N0 - Hydraulic Fluids

Relations

• Replaces: ASTM D6547-16 - Standard Test Method for Corrosiveness of Lubricating Fluid to Bimetallic Couple
• Effective Date: 15-Dec-2023
• Refers: ASTM D4175-23a - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 15-Dec-2023
• Refers: ASTM D4175-23e1 - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 01-Jul-2023

Overview

ASTM D6547-23, "Standard Test Method for Corrosiveness of Lubricating Fluid to Bimetallic Couple," establishes procedures to determine the corrosive effects of hydraulic and lubricating fluids on a bimetallic (brass-on-steel) galvanic couple. This method is critical for evaluating fluid compatibility with common metal pairings found in hydraulic and lubricated equipment. Developed under internationally recognized principles, this standard ensures reliable testing procedures aligned with global expectations for safety and quality.

The method replicates the procedures and evaluation criteria of Fed-Std No. 791, Method 5322.2, providing users with explicitly described test procedures and robust pass/fail outcomes.

Key Topics

• Test Scope: Focuses on assessing the corrosiveness of various hydraulic and lubricating fluids in contact with a brass-on-steel galvanic couple.
• Test Procedure Overview:
  • Preparation of steel disks and brass clips, following ASTM and Fed-STD references.
  • Application of test fluid, assembly of the bimetallic couple, and exposure to 50% relative humidity at ambient temperature for ten days.
  • Inspection for galvanic corrosion, pitting, or discoloration using a 10× magnifier.
• Result Evaluation:
  • Determination of fluid's pass/fail status based on visible corrosion or pitting.
  • Ensures only fluids compatible with bimetallic systems proceed to use.
• Safety and Compliance:
  • Emphasizes the need for appropriate health, safety, and environmental practices.
  • Users are responsible for adherence to applicable regulations.

Applications

ASTM D6547-23 is valuable for industries where hydraulic and lubricating fluids interact with bimetallic assemblies, such as:

• Automotive and Heavy Equipment: Verifying lubricants and hydraulic fluids for use in vehicles and machinery with mixed metal components.
• Aerospace and Defense: Ensuring hydraulic fluids meet rigorous corrosion-resistance benchmarks for mission-critical systems.
• Industrial Manufacturing: Selecting compatible fluids for equipment with brass and steel interfaces to prevent galvanic corrosion.
• Fluid Development and Quality Control: Used by formulators and laboratories to screen new lubricants for bimetallic compatibility before field deployment.
• Regulatory Compliance: Assisting manufacturers and suppliers in meeting DOD or international procurement requirements referencing corrosion standards.

By applying this standard, organizations reduce maintenance costs, extend component lifespans, and improve operational reliability in metal-fluid systems.

Related Standards

Users of ASTM D6547-23 may also find the following standards relevant:

• ASTM A322: Specification for Steel Bars, covering steel grades used for test disks.
• ASTM D4175: Terminology relating to petroleum products, liquid fuels, and lubricants.
• FED-STD-791, Method 5322.2: Federal method for testing oil corrosiveness on bimetallic couples, mirrored in this ASTM standard.
• Other ASTM D02 Committee Standards: For comprehensive evaluation of hydraulic fluids and lubricants, consult related ASTM D02 documents.

This standard supports best practices in the selection, qualification, and ongoing evaluation of lubricating and hydraulic fluids where metal compatibility is essential.

Keywords: ASTM D6547, lubricating fluid, hydraulic fluid, bimetallic corrosion, galvanic couple, brass-steel corrosion, fluid compatibility testing, corrosion test method, fluid quality control, test standards for lubricants.

Standards Content (Sample)

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.
Designation: D6547 − 23
Standard Test Method for
Corrosiveness of Lubricating Fluid to Bimetallic Couple
This standard is issued under the fixed designation D6547; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* 3. Terminology
3.1 Definitions:
1.1 This test method covers the corrosiveness of hydraulic
and lubricating fluids to a bimetallic galvanic couple. 3.1.1 For definitions of terms used in this test method, refer
to Terminology D4175.
NOTE 1—This test method replicates Fed-Std No. 791, Method 5322.2.
It utilizes the same apparatus, test conditions, and evaluation criteria, but
4. Summary of Test Method
it describes test procedures more explicitly.
1.2 The values stated in SI units are to be regarded as
4.1 This test method consists of fitting a brass clip to the
standard.
fluid-coated surface of a steel disk, storing the assembly at
1.2.1 Exception—The values given in parentheses are for
approximately 50 % relative humidity for ten days, and visu-
information only.
ally inspecting the assembly for evidence of galvanic corro-
sion.
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
5. Significance and Use
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
5.1 Corrosiveness of a fluid to a bimetallic couple is one of
mine the applicability of regulatory limitations prior to use.
the properties used to evaluate hydraulic or lubricating fluids.
1.4 This international standard was developed in accor-
It is an indicator of the compatibility of a fluid with a brass on
dance with internationally recognized principles on standard-
steel galvanic couple at ambient temperature and 50 % relative
ization established in the Decision on Principles for the
humidity.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
6. Apparatus
Barriers to Trade (TBT) Committee.
6.1 Desiccating Jars, two.
2. Referenced Documents 6.2 Magnifier, 10× power.
2.1 ASTM Standards: 6.3 Glass Stirring Rod.
A322 Specification for Steel Bars, Alloy, Standard Grades
6.4 Abrasive Papers, silicon-carbide or aluminum oxide
D4175 Terminology Relating to Petroleum Products, Liquid
(150, 240, 400, 600 grit, one sheet per disk).
Fuels, and Lubricants
6.5 Cloth, lint-free, clean, dry.
2.2 Federal Standards:
6.6 Chromium Alloy Steel Disks, three for each test sample.
FED-STD-791, Method 5322.2 Corrosiveness of Oil on a
Bimetallic Couple
6.7 Brass Clips, three for each test sample.
7. Reagents and Materials
This test method is under the jurisdiction of ASTM Committee D02 on
7.1 Purity of Reagents—Reagent grade chemicals shall be
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
used in all tests. Unless otherwise indicated, it is intended that
Subcommittee D02.N0 on Hydraulic Fluids.
Current edition approved Dec. 15, 2023. Published December 2023. Originally
approved in 2000. Last previous edition approved in 2016 as D6547 – 16. DOI:
10.1520/D6547-23.
2 4
For referenced ASTM standards, visit the ASTM website, www.astm.org, or The sole source of supply of the apparatus known to the committee at this time
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM is Metaspec, 790 W. Mayfield Rd., San Antonio, TX 78211. If you are aware of
Standards volume information, refer to the standard’s Document Summary page on alternative suppliers, please provide this information to ASTM International
the ASTM website. Headquarters. Your comments will receive careful consideration at a meeting of the
3 1
Available online at ASSIST Quicksearch (http://quicksearch.dla.mil). responsible technical committee, which you may attend.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6547 − 23
all reagents conform to the Committee on Analytical Reagents to 1.0 in.) thick. Prior to initial use, the steel disk shall be
of the American Chemical Society where such specifications ground on one side to a 0.51 μm (20 μin.) rms. This treatment
are available. need not be repeated prior to reuse.
8.1.2 Polish the surface of the ground side using 150, 240,
7.2 Etching Solution, consisting of distilled water, 450 mL;
400, and 600-grit silicon carbide or aluminum oxide paper in
nitric acid, concentrated, 225 mL; sulfuric acid, concentrated,
succession. Use one sheet of each per disk. Perform each
300 mL; and hydrochloric acid, concentrated, 8 mL.
polishing operation at right angles to the previous one, and
7.2.1 To avoid hazardous reactions when preparing the
continue until all the cross scratches from the previous opera-
etching solution, place the distilled water (450 mL) in a 1.5 L,
tion are removed.
or larger, glass beaker set in a container of ice and water. Stir
with a glass mechanical stirrer or plastic coated magnetic spin
NOTE 5—Hand polishing techniques were used exclusively in the round
robin evaluation of this test method. Mechanical polishing was not
bar while slowly adding concentrated sulfuric acid (300 mL).
evaluated and may not yield equivalent results.
Add more ice to the cooling bath as needed. When acid
addition is complete, continue stirring until the solution has 8.1.3 Clean the disks by wiping with a clean, dry, lint-free
cooled to room temperature, and then start slow addition of the cloth, being careful not to touch the polished surfaces with bare
concentrated nitric acid (225 mL). Continue stirring after acid hands.
addition until the solution has cooled to room temperature, and 8.1.4 Examine with a 10× power magnifier for
then add concentrated hydrochloric acid (8 mL). Allow the discoloration, etching, pitting, or other signs of corrosion.
mixture to equilibrate to room temperature before use. Discard disks with any signs of corrosion.
(Warning—Nitric, hydrochloric, and sulfuric acids are very 8.1.5 Store the disks in a desiccator containing desiccant
corrosive. Nitric acid and sulfuric acid are also oxidizing acids. until time of use.
The analyst should prepare the etching solution in a well-
8.2 For each test fluid, prepare three brass clips. These brass
v
...

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: D6547 − 16 D6547 − 23
Standard Test Method for
Corrosiveness of Lubricating Fluid to Bimetallic Couple
This standard is issued under the fixed designation D6547; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope*
1.1 This test method covers the corrosiveness of hydraulic and lubricating fluids to a bimetallic galvanic couple.
NOTE 1—This test method replicates Fed-Std No. 791, Method 5322.2. It utilizes the same apparatus, test conditions, and evaluation criteria, but it
describes test procedures more explicitly.
1.2 The values stated in SI units are to be regarded as standard.
1.2.1 Exception—The values given in parentheses are for information only.
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 and healthsafety, health, and environmental 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
2.1 ASTM Standards:
A322 Specification for Steel Bars, Alloy, Standard Grades
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
2.2 Federal Standards:
FED-STD-791, Method 5322.2 Corrosiveness of Oil on a Bimetallic Couple
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this test method, refer to Terminology D4175.
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.N0 on Hydraulic Fluids.
Current edition approved Jan. 1, 2016Dec. 15, 2023. Published February 2016December 2023. Originally approved in 2000. Last previous edition approved in 20102016
as D6547 – 00 (2010).D6547 – 16. DOI: 10.1520/D6547-16. 10.1520/D6547-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available online at ASSIST Quicksearch (http://quicksearch.dla.mil).
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6547 − 23
4. Summary of Test Method
4.1 This test method consists of fitting a brass clip to the fluid-coated surface of a steel disk, storing the assembly at approximately
50 % relative humidity for ten days, and visually inspecting the assembly for evidence of galvanic corrosion.
5. Significance and Use
5.1 Corrosiveness of a fluid to a bimetallic couple is one of the properties used to evaluate hydraulic or lubricating fluids. It is
an indicator of the compatibility of a fluid with a brass on steel galvanic couple at ambient temperature and 50 % relative humidity.
6. Apparatus
6.1 Desiccating Jars, two.
6.2 Magnifier, 10× power.
6.3 Glass Stirring Rod.
6.4 Abrasive Papers, silicon-carbide or aluminum oxide (150, 240, 400, 600 grit, one sheet per disk).
6.5 Cloth, lint-free, clean, dry.
6.6 Chromium Alloy Steel Disks, three for each test sample.
6.7 Brass Clips, three for each test sample.
7. Reagents and Materials
7.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents conform to the Committee on Analytical Reagents of the American Chemical Society where such specifications are
available.
7.2 Etching Solution, consisting of distilled water, 450 mL; nitric acid, concentrated, 225 mL; sulfuric acid, concentrated, 300 mL;
and hydrochloric acid, concentrated, 8 mL.
7.2.1 To avoid hazardous reactions when preparing the etching solution, place the distilled water (450 mL) in a 1.5 L, or larger,
glass beaker set in a container of ice and water. Stir with a glass mechanical stirrer or plastic coated magnetic spin bar while slowly
adding concentrated sulfuric acid (300 mL). Add more ice to the cooling bath as needed. When acid addition is complete, continue
stirring until the solution has cooled to room temperature, and then start slow addition of the concentrated nitric acid (225 mL).
Continue stirring after acid addition until the solution has cooled to room temperature, and then add concentrated hydrochloric acid
(8 mL). Allow the mixture to equilibrate to room temperature before use. (Warning—Nitric, hydrochloric, and sulfuric acids are
very corrosive. Nitric acid and sulfuric acid are also oxidizing acids. The analyst should prepare the etching solution in a
well-ventilated hood and wear appropriate gloves, apron, and face shield.)
7.3 Acetone, technical grade. (Warning—Flammable. Health hazard.)
7.4 Distilled Water.
The sole source of supply of the apparatus known to the committee at this time is Metaspec, 790 W. Mayfield Rd., San Antonio, TX 78211. If you are aware of alternative
suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical
committee, which you may attend.
Reagent Chemicals, American Chemical Society Specifications,ACS Reagent Chemicals, Specifications and Procedures for Reagents and Standard-Grade Reference
Materials, American Chemical Society, Washington, DC. For Suggestionssuggestions on the testing of reagents not listed by the American Chemical Society, see
AnnualAnalar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharmacopeial
Convention, Inc. (USPC), Rockville, MD.
D6547 − 23
NOTE 2—Both distilled and deionized water were used in the round robin with no apparent impact on test outcome.
7.5 Saturated Aqueous Solution , Solution, in contact with excess calcium nitrate tetrahydrate.
NOTE 3—A saturated aqueous solution in contact with an excess of Ca(NO ) · 4H O will produce 51 % relative humidity within a closed space at 25 °C.
3 2 2
To prepare the saturated solution,
...