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    ASTM G69 - 20

    Standard Test Method for Measurement of Corrosion Potentials of Aluminum Alloys

    Active Standard ASTM G69 | Developed by Subcommittee: G01.11

    Book of Standards Volume: 03.02

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    Significance and Use

    3.1 The corrosion potential of an aluminum alloy depends upon the amounts of certain alloying elements that the alloy contains in solid solution. Copper and zinc, which are two of the major alloying elements for aluminum, have the greatest effect with copper shifting the potential in the noble or positive direction, and zinc in the active or negative direction. For example, commercially unalloyed aluminum (1100 alloy) has a potential of –750 mV when measured in accordance with this method, 2024–T3 alloy with nearly all of its nominal 4.3 % copper in solid solution, a potential of –600 mV to –620 mV, depending upon the rate of quenching and 7072 alloy with nearly all of its nominal 1.0 % zinc in solid solution, a potential of –885 mV (SCE) (1-3).3

    3.2 Because it reflects the amount of certain alloying elements in solid solution, the corrosion potential is a useful tool for characterizing the metallurgical condition of aluminum alloys, especially those of the 2XXX and 7XXX types, which contain copper and zinc as major alloying elements. Its uses include the determination of the effectiveness of solution heat treatment and annealing (1), of the extent of precipitation during artificial aging (4) and welding (5), and of the extent of diffusion of alloying elements from the core into the cladding of Alclad products (2).

    1. Scope

    1.1 This test method covers a procedure for measurement of the corrosion potential (see Note 1) of an aluminum alloy in an aqueous solution of sodium chloride with enough hydrogen peroxide added to provide an ample supply of cathodic reactant.

    Note 1: The corrosion potential is sometimes referred to as the open-circuit solution or rest potential. See Terminology G193.

    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, 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 (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    D1193 Specification for Reagent Water

    E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method

    G3 Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing

    ICS Code

    ICS Number Code 77.120.10 (Aluminium and aluminium alloys)

    UNSPSC Code

    UNSPSC Code 41114604(Corrosion testers)

    Referencing This Standard
    Link Here
    Link to Active (This link will always route to the current Active version of the standard.)

    DOI: 10.1520/G0069-20

    Citation Format

    ASTM G69-20, Standard Test Method for Measurement of Corrosion Potentials of Aluminum Alloys, ASTM International, West Conshohocken, PA, 2020, www.astm.org

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