Inhibition of steel and galvanised steel corrosion by zinc and calcium ions in the presence of phosphate

I. M. Zin, S. B. Lyon, V. I. Pokhmurskii, M. C. Simmonds

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    Mixtures of zinc, calcium and phosphate ions have been found to be effective (>90%) in inhibiting the corrosion of steel and zinc during immersion in acid rain solution and when used as pigment additions to organic coatings. The presence of calcium ions, in addition to zinc ions, appears to be fundamental in the inhibition mechanism since, in the absence of calcium, the inhibition efficiency is 50% or less. Although some anodic inhibition occurs, the predominant mechanism appears to be classical cathodic inhibition caused by the precipitation of a sparingly soluble, thin, but persistent, solid film. Surface analysis, by XPS, confirms that phosphorus is present in the form of phosphate species containing zinc and calcium. Also, the atomic ratios of zinc:calcium:phosphorus present in the inhibitive film strongly suggest that it consists of a mixture of CaZn2(PO4)2 (Scholzite) and Zn3(PO4)2 (Hopeite) in a 1:1 ratio. © 2004 IoM Communications Ltd. Published by Maney for the Institute of Materials, Minerals and Mining.
    Original languageEnglish
    Pages (from-to)167-173
    Number of pages6
    JournalCorrosion Engineering Science and Technology
    Issue number2
    Publication statusPublished - Jun 2004


    • Galvanised steel
    • Inhibitor
    • Organic coating
    • XPS


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