We are having a problem with staining on a number of our final rinses. In particular, the final rinses in our nickel and gold lines are giving us staining. We are using multiple step cascading rinses and hot air drying. Do you have any suggestions on how we can eliminate this problem? D. D.
Your question doesn’t say much about the type of staining but I assume that it is staining caused by drying of the rinse water. There are a few things you can do.
- You can add a rinse or replace one of your current rinses with a D. I. water rinse. If the final rinse contains minimal impurities, the staining will be reduced.
- You can add a small amount of a wetting agent to provide “sheeting action” in the final rinse step. This is similar to the drying agent that is placed in a kitchen dishwasher to prevent staining of glassware.
- You can reduce the temperature of your dry off step so that the salts that are present in the water do not baked onto the surface. The dry off temperature should be in the 120–130°F range.