Chrome-Nickel Screens and Pitting

Q. Our company manufactures screens used in continuous centrifugal machines in sugar mills. The screens we are shipping this year start pitting after 11 days of use, whereas the screens we previously supplied did not show any pitting until 20-25 days of use. The chromium plate is 15 microns thick and has a hardness of more than 900 HV. What other parameters should we check? K.I.

A. Your e-mail doesn’t give me much information for solving your problem, but your question can be used as a starting point for a troubleshooting process. The first thing to keep in mind is that taking the plated part out of the process as-sumes that the problem is with the plated part. This may or may not be the case. If indeed the plated part is the problem, then you should determine whether the thickness of the chromium plate is the same on the parts produced this year as those produced last year.

However, before looking at the plated part, I would look at the process in which this part is being used. Quite often, a manufacturing process is changed because of changes in raw materials, or a stealth change is made without anybody being told.