STP866

    Applications of Electrochemical Techniques in Screening Metallic-Coated Steels for Atmospheric Use

    Published: Jan 1985


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    Abstract

    Electrochemical tests were conducted on several aluminum-zinc-coated steels whose long-term atmospheric corrosion resistance is known in order to evaluate such tests as a screening technique. Linear polarization resistance measurements were made in aerated 1 N sodium chloride and 0.5 N sodium sulfate both at pH 4 to rank the different coatings and then compare this ranking with that found in marine and industrial environments. Weight loss was also measured, and the specimens were examined microscopically to verify the corrosion mechanism. Cathodic polarization tests were conducted in deaerated 1 N hydrochloric acid and 1 N sulfuric acid to examine a system with only one cathodic reaction. The results obtained in the pH 4 chloride and sulfate solutions were in good general agreement with the data from atmospheric exposures. Thus polarization resistance testing in 1 N sodium chloride and 0.5 N sodium sulfate at pH 4 shows promise as a screening technique for predicting the atmospheric corrosion resistance of metallic-coated steels.

    Keywords:

    galvanic corrosion, atmospheric corrosion, polarization, electrochemical testing, linear polarization, polarization resistance, corrosion potential, Tafel slope, potentiodynamic polarization, metallic-coated steel, galvanized steel


    Author Information:

    Berke, NS
    Senior research engineer, W. R. Grace and Co., Cambridge, MA

    Friel, JJ
    Senior research engineer, W. R. Grace and Co., Cambridge, MA


    Paper ID: STP33775S

    Committee/Subcommittee: G01.11

    DOI: 10.1520/STP33775S


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