Ask the Expert Question-and-Answer Archive

by Ron Joseph

March, 2009

How to Achieve Higher DFT per Coat

Q. Is it possible to get higher DFT per coat than that specified in paint supplier's technical datasheet? If yes please advise how?

One of our customers asking 80 micron DFT per coat where as paint supplier's data indicate 40 micron DFT per coat.

A. It is possible to get a higher dry film thickness than what is specified by the paint manufacturer; however, if you exceed the recommended thickness you might run into problems. The most common paint defects or failures are due to solvent entrapment, softness, runs and sags. Obviously, runs and sags are visual and detract from the appearance of the painted product. Solvent entrapment takes place when the paint film starts to cure before the solvents (or water) can fully evaporate, and this leads to blistering and paint peeling. In fact, when this defect occurs, paint can peel in sheets ... something nobody likes to experience.

If you want to achieve 80 microns, but the vendor recommends 40 microns, you must apply two coats. In other words, apply the first coat, let the solvents evaporate and then apply the second coat. Do not try to apply 80 microns in a single coat or you might experience the problems mentioned above.

Regards,

Ron Joseph