Why do the lead anodes in our mixed catalyst chromium plating bath turn yellow? The chrome is applied over a nickel layer. F.N.
If your chromium plating bath is shut down for any period of time, lead chromate will form on the surface of the anodes. As you probably have found out, this layer of lead chromate reduces the activity of the anode. Depending on the severity of the problem, there are two solutions you can use. If the anodes have only a small amount of lead chromate on the surfaces, try dummying the anodes before you start plating. The color of the anodes should change to brown after dummying.
If the anodes have a heavier coating of lead chromate, the anodes will have to be cleaned using a suitable immersion cleaner. There are a number of proprietary immersion cleaners available for cleaning of lead anodes. Talk to your chemical vendor or look in the 2003 Products Finishing Directory and Technology Guide under Cleaning Chemicals, aqueous or go to www.pfonline.com/clean/suppliers.html.