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Abstract
An investigation was carried out to determine the aqueous corrosion performance of the Metco 15F commercial Ni-Fe-Cr-B-Si-C alloy coating. Such coatings are frequently used in engineering applications where a combination of high wear and high corrosion resistance is required. Accordingly, the coating has sometimes been specified to improve the wear durability of austenitic stainless steel. A series of immersion and cyclic voltammetry (potentiodynamic polarisation) tests, including linear polarisation resistance measurements, were carried out in various corrosive media with 317 LMN austenitic stainless steel, both with and without a surface coating of 15F. The coated stainless steel was less corrosion resistant than the uncoated steel. However, the coating/substrate interface was particularly prone to corrosion attack, resulting in delamination of the coating during immersion testing. The intrinsically poor corrosion resistance of the 15F coating is attributed to one or more of the principal hard precipitates (probably Cr7C3), which preliminary results suggest is anodic relative to the nickel based solid solution matrix.