Q. Our job shop plates industrial hard chrome. Over the years, we have been told that only deionized water should be used for make-up in the chrome tanks, but we do not use deionized water. Why is this necessary?—T.Y.
A. The quality of water used for plating bath make-up is an extremely important factor in maintaining good plating bath control. Tap water contains a variety of things that may be just fine for drinking but not so fine for plating. This includes chlorides, which reduce current efficiency and create difficulties in controlling the catalyst concentration. Drinking water may also contain small amounts of fertilizer run-off such as nitrates and phosphates, which can cause a gray deposit in chrome plating, and calcium salts, which will build up in plating tanks and precipitate out, causing roughness problems. The bottom line is: Always use deionized water for make-up in a chrome plating bath. In fact, this is a good rule to follow for all types of plating baths.