I've thought about how to detect if a part is zinc or cad plated. The answer might be in the full strength muratic acid bath I've been using prior to plating.
Unplated items fizz very little.
But even after media blasting the cad parts fizz pretty well.
Maybe that's a good test?
The way I have been removing zinc or cad plating is to first use the muriatic acid bath until the parts stop fizzing. Then I media blast them with glass bead to give them a good polish which really helps the quality of the plating, and then a quick dip in the acid again before re plating. I have found no difference between the cad and the zinc in the 20% solution I have been using. They both seem to react the same way and take the same amount of time to strip. Media blasting only will not remove all of the plating, so best to soak in the acid bath, otherwise the re plating will not turn out well in my experience. FYI prepping parts for Phosphate, I have found only require media blasting, but I have also been doing a quick muriatic dip before phostophating as well to make sure that I get a good coating. It seems to improve the process. Fore any of these processes they key is very clean and pure metal surfaces. As has been pointed out often, even a finger tip can leave oils on the part and affect the plating process in a negative way
