Paints & Coatings Resource Center

Ask the Expert Question-and-Answer Archive

by Ron Joseph

March, 2006

Class (Classification) of Finish Quality

Q. Is there any written explanation to the different finish qualities that powder coaters achieve? As an example powder coaters refer to class "A" , "B", "C" finishes. We have a customer that the print calls for a class "B" finish which in our view as a custom coater we have achieved, but they say we need to be 3-8 mils thick for this, but I found out that the thickness is more related to a later assembly issue than a appearance issue. I"m just looking for some type of documentation to show the differences of powder coaters views on the different classes.

A. To the best of my knowledge there is no formal specification that defines Class A, B or C. Usually, a finish quality is based on the number and types of defects that can be seen from a specified distance. In my opinion, you and your customer should have agreed on your mutual understanding of Class B before commencing the work. Sometimes, a color chip is made as a standard before the contract commences so that you can use it later for determining what is acceptable and what is a reject.

I am certainly not aware of any specification that defines finish quality as a function of coating film thickness.

Best wishes,

Ron Joseph

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