Rinsing Problems Again

Q: We triple rinse our parts after our final decorative chromium plating step. However even with this type of rinsing, we end up with spotted parts after drying. K. E.

 

A: Your problem is a relatively simple one to solve. I suspect you are using hard water in your final rinse steps. I would suggest the following sequence: Use two cold water rinses followed by a hot water rinse. Follow-up with a final rinse of deionized water.

This problem surfaces more frequently than we would like to admit. The author visited a plating facility a few years ago in which the plated parts were run through a reasonable rinse sequence and then a drying oven. The problem they were having similar to that mentioned in the above e-mail. As I walked the line, I noticed that there were a number of spray heads prior to the drying step that were not working. Asking my host why these spray heads were not working, I was told that the DI water system had gone down the previous week and it had not been repaired. At that moment, the plant manager had a light bulb go on and immediately went to his office to call maintenance. The plant is located in an area of the United States that had fairly hard water and when the plating line was installed, DI water sprays were specified to remove the last traces of the hard water.
From my perspective this was perhaps one of the easiest consulting gigs I ever had but it does point out that quite often in the world of plating we overlook the obvious.