Hard Chrome Plating Cast Iron

Q. We are a job shop hard chrome plater. Occasionally, we have problems with plating on cast iron. Mainly passive areas on cast plates. Can you offer any suggestions?

A. a couple things come to mind, but first, any chance you can float me a photo or two of the troubled area? Secondly, I assume you are using standard prep & start up procedures when plating "cast iron"? Whether the part you are chrome plating was bran new, or an older part being refurbished, a clean surface is a must with cast iron. Are all surface contaminants removed, i.e., paint, grease, corrosion, etc.??

Here are some suggestions, to start, solvent clean, possibly even an Alkaline electro-clean using periodic reverse, or at least a "dry blast" using aluminum oxide or equivalent, wear clean cotton gloves when handling after blast or electro-cleaning. Warm part up in the chrome bath prior to application of current, warm up time based on part size and girth. Then fixture some additional conforming anodes in troubled areas, NO REVERSE ETCH., after warm up only, start plating forward polarity, striking the current initially for the first 3-10 minutes ( 4-5 asi +), then backing it back down to standard plating rate for the duration.? Keep bath temp in range, ensure you have enough "DC amps and good clean DC electrical connections.

If you can send photos to illustrate your problem, it may shed light on the problem(s).

Randy Taylor