Abstract
Alternate layers of nickel on zinc and zinc on nickel have been electrodeposited on a steel substrate to yield a multilayer system in order to enhance its corrosion resistance. The coatings have been characterised in terms of surface appearance and their surface and crosssectional morphologies. Corrosion resistance has been measured by means of salt spray accelerated testing and the results have been compared with that of a zinc deposit alone. It has been found that direct deposition of nickel on zinc as well as the production of alternating layers of nickel followed by zinc or zinc followed by nickel on a steel substrate are possible. The corrosion performance of these types of multiple layers (each of 1, 2, or 4 μm thickness, with a total thickness of 8 μm) has been found to be better than that of a single-layer zinc deposit. What is more, for this total thickness, salt spray resistance (measured by the area percentage of red rust after a given time) increases as the number of individual layers increases. This is because ofthefiner structure in each thin layer and the multiple layer effect.
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