Corrosion performance of decorative electrodeposited nickel and nickel-iron alloy coatings. Discussion. Authors' closure

The corrosion performance of chromium-electroplated, decorative nickel and nickel-iron alloy electrodeposits has been studied in marine and industrial atmospheres and by means of copper-accelerated acetic acid-salt spray testing (CASS). Decorative nickel coatings, 15 and 30 μm thick, gave better overall corrosion performance than comparable decorative nickel-iron alloy coatings. Because of the rapid staining that occurs in marine and industrial atmospheres, nickel-iron alloy deposits are not suitable for decorative applications involving moderate and severe corrosion service. Decorative nickel-iron alloy deposits, 7.6 μm thick, appear suitable for mild corrosion service on the basis of CASS test results, but results were affected by iron content and type of electrodeposited chromium. The relatively good performance of thin alloy deposits accounts for established applications in mildly corrosive environments. The performance of the decorative electrodeposited nickel coatings was influenced by the activity of bright nickel. Low-activity single-layer bright nickel (15 μm) performed better than high-activity bright nickel when used with microporous or microcracked chromium. High-activity double-layer nickel (30 μm) protected low-current-density areas of contoured steel panels better than low-activity double-layer nickel, either with microporous or microcracked chromium. Microporous chromium was more effective in this program; microcracked chromium was more effective in a previous study.