Metal Finishing Guide Book


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Table IX: Comparison of Zinc Alloy Plating Processes Plating Bath Zn Alkaline Sn-Zn Neutral Appearance B C B B B B Solderability C A D D D D Wear-resistance C D A A C C Whisker D B B B D D Crimping, bending Zn-Ni Alkaline Zn-Ni Acid Zn-Co Acid Zn-Fe Alkaline B A B D C C White C C A A C C Red C A A A C C White D C A B D D Red C C A C D D White C C A C D D Red C A A C D D Throwing power A C A D A A Plating rate C B C A C C Covering power B A B B B B Bath control A B B D C C Blue Yellow Black Clear Clear Black Clear Black Clear Yellow Black General Corrosion After resistance baking After crimping Chromate availability Replatability A C C C B B Zinc/ steel Tin/zinc alloy Nickel plated Zinc/ nickel Zinc Zinc Auxiliary anode A C A D A A Waste water B B C C B B X-ray A B B B B B Kocour A B B C B B X-ray - B B C D D Analysis - B B B C D 1.0 2.5���3.0 2.5���3.0 1.5 1.2 1.1 Anodes Thickness Composition Relative price A: Excellent B: Good C: Fair D: Poor electroplated strip steel. It is also suitable as a base for paint. Of the alloys being considered, zinc-iron will generally give the least improvement in corrosion resistance compared with conventional zinc. If the iron content of the bath gets too high, blistering problems, including delayed blistering, may occur. Corrosion resistance of chromated zinc-iron plated parts drops drastically after exposure to temperatures over 250��F (see Tables V and VI for acid and alkaline bath parameters). TIN-ZINC A number of electrolytes are available for deposition of tin-zinc alloys. These 364

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