STP516: Relative Critical Potentials for Pitting Corrosion of Some Stainless Steels

    Johnson, MJ
    Senior research chemical engineer, Allegheny Ludlum Industries, Inc., Research Center, Brackenridge, Pa.

    Pages: 11    Published: Jan 1972


    Abstract

    The breakthrough potentials of stainless steel alloy Types 409, 304, and HWT were determined in solutions containing various concentrations of chloride ion, ranging from 10 to 40,000 ppm. Four different salts were used to introduce the chloride ion: sodium chloride, calcium chloride, cupric chloride, and ferric chloride. The breakthrough potential values obtained decreased with increasing chloride ion concentration. These breakthrough potential values were plotted against the logarithm of the chloride ion concentration and a straight line drawn through the lowest potential points for each alloy. This line described the minimum pitting potentials for each alloy and was used to compare the three alloys studied. Using this method, HWT proved to be a more pit resistant alloy than Type 304 which in turn was more pit resistant than Type 409.

    Keywords:

    corrosion, pitting, stainless steels, austenitic stainless steels, polarization, anodic polarization


    Paper ID: STP35425S

    Committee/Subcommittee: G01.11

    DOI: 10.1520/STP35425S


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