We plate SG iron castings in a zinc acid chloride plating bath and then chromate with a classic hexavalent yellow chemical conversion bath. We recently we tried a trivalent yellow conversion coating, but after processing 30–40 jobs we observe black patches on the jobs immediately after processing. Is it possible that the iron impurities from the casting contaminate the chemical conversion bath and if so, how we can control the process?
Since switching our supplier of sodium sulfide and sodium hypophosphite used in our electroless nickel plating baths, we have had problems such as brown stains and plating out of nickel on the tank walls. Do you have any suggestions for resolving these problems?
We selectively strip gold from using a reel-to-reel process. Quite often, the gold that remains after the stripping process is a dark, brown-gold color. Do you have any suggestions for how to fix this problem?
We use a nickel sulfamate plating bath with a temperature range of 50–60°C to plate low stress micro-layers. Recently the temperature was allowed to reach 70°C. Did we ruin the plating bath because of this temperature upset? Can the plating bath be salvaged?