STP1134

    Time-Lapse Video Techniques in the Corrosion Testing of Aluminum Alloys

    Published: Jan 1992


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    Abstract

    This paper describes the use of time-lapse video techniques for in situ observation during controlled and free corrosion of high-strength Al-Zn-Mg-Cu alloys 7075 and 7150 and two Al-Zn binary alloys. Direct observation of corroding 7075 in various tempers shows that, as a precursor to stable pit formation, a deformable gelatinous layer of corrosion product develops. Gas is evolved at the metal/hydrated oxide interface, which distorts the gel layer at potentials below those expected for pitting. During stress corrosion cracking of 7150 T6, time-lapse video images confirm that initial drying after total immersion of 0.6M NaCl solution leads to an acceleration in the apparent rate of crack growth from 5 × 10-7 m/s to 9 × 10-6 m/s. This rate is sustained for only a few minutes but could help explain the aggressive nature of alternate immersion testing.

    Keywords:

    aluminum alloys, corrosion, time-lapse video, stress corrosion cracking, alternate immersion


    Author Information:

    Newton, CJ
    Research metallurgist and senior consulting scientist, Alcan International Ltd., Banbury Laboratories, Banbury, Oxfordshire

    Holroyd, NJH
    Research metallurgist and senior consulting scientist, Alcan International Ltd., Banbury Laboratories, Banbury, Oxfordshire


    Paper ID: STP19588S

    Committee/Subcommittee: G01.11

    DOI: 10.1520/STP19588S


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