Ask the Expert Question-and-Answer Archive

by Ron Joseph

February, 2004

Chromium VI in Paint

Q. This week a question has been posed that has us stumped and I was hoping that you might have a research source or two that we might pursue. The question involves the blasting (plastic media in this case) of painted on corrosion resistant paints and primers that contained Chromium VI when they were first applied. The specific matter of concern is whether the Chromium VI compounds will be found in blasting dust to any significant degree or whether these compounds react over time and would actually be found as Chromium III.

Any direction that you might provide would be of assistance.

A. As to your first question, the abrasive will contain all the paint debris that has not been separated from the process. It the plastic media is recycled or reused without first separating the paint debris then the concentration of paint in the media will be high.

Your second question relates to Chromium VI or Chromium III. Cr6+ is present in the paint as a pigment and not as a chemical salt. Therefore, to the best of my knowledge there will be no chemical change with age, anymore so than if the paint were still on the sheet metal prior to abrasive blasting. I expect that you will find Cr6+ for the remainder of the paint's life.