Ask the Expert Question-and-Answer Archive

by Ron Joseph

November, 2005

Solving Paint Cratering Problems

Q. I work within the automotive industry, mainly in ED coat and sealing. For the past 2 months I have suffered from craters. These craters after being analysised looked to be weld spatter/weld balls on top of the ED coat. After going being primered the craters were seen straight away in the wet coat. Nothing is visible on the ED coat after ovenbake.

Do you have any direction what could cause this defect?

A. Unfortunately you are asking about one of the most elusive problems in the paint industry. Even Sherlock Holmes would find this one difficult to solve! The contaminants might come from an obvious source near to the painted surface or might be carried in the air over long distances from within the factory or perhaps even from an outside source. I'm not surprised that you have been working unsuccessfully on this paint failure (defect) for the past 2 months.

Chemical analysis might lead you to the nature or composition of the contaminant, but then you will still need to identify the source. You might find that your air ducts and/or oven are already contaminated and this would require you to clean out the system before eliminating the problem.

As a paints and coatings consultant I would be happy to assist you by visiting you on-site and performing a very thorough review of the entire operation. I have done such work before and know that it can be a laborious task, and there is no guarantee of success. Basically, I would conduct a series of tests to try to isolate the failure.

Sorry for such an unhelpful answer, but if you would like to pursue this further please visit my web site www.ronjoseph.com to see my credentials. If you would like to work with me please don't hesitate to get back to me.

Best wishes,

Ron Joseph