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QUESTION

Our company has experienced a serious finish failure on one of our jobs. The topcoat is delaminating from the finish. We use a post-catalyzed sealer. It was sanded with 320-grit sandpaper after it dried for one hour. The finish was glazed with an oil glaze on the same day it was sealer-sanded. A topcoat of catalyzed conversion varnish is the manufacturer’s recommended re-coat window after the glaze was dried. All the coating manufacturer’s recommendations were followed for application procedures. Before the job was sent out to the customer, we realized the topcoat could be scratched off the glaze just by using a fingernail. What went wrong? Please help!

ANSWER

It is hard to diagnose the problem without examining the sample. You followed all the manufacturer’s recommendations for the correct material to use in the finishing system and followed its recommended dry times between finishing steps. We must then conclude that there are only three other possible root causes for the finish to fail.

If the topcoat was applied at the wrong wet mil thickness, the coating will not bond securely to the glaze and could result in a delamination problem.

Secondly, if the topcoat was not catalyzed at the correct ratio, it will cause this type of finish failure. This is the most plausible cause of your problem.

If you are uncertain whether the topcoat was catalyzed correctly, you should send a hard sample to be tested to check the acidity of the coating to determine if it was over or under catalyzed.

If the coating was catalyzed properly and applied in strict accordance with the manufacturer’s recommendations, you should then have the coating manufacturer analyze the finish failure for chemistry problems. You may be experiencing a coating batch problem or some other unknown coating chemistry problem.