How To Troubleshoot Automotive Paint: Causes and Cures


Rust under film

Caused by presence of rust on surface before finishing—and no paint will adhere to a rusty surface. To avoid this, always sand all rust spots bright and treat bare metal with a metal conditioner such as “Deoxidine,” “Metalprep,” etc., before finishing. Wash with water and dry thoroughly. Always prime the surface immediately after cleaning, as rust will set in if bare metal is exposed too long.

Wrinkling of Dulux


  • Application of excessive number of coats improperly dried between coats.
  • Overloading of one or more coats.
  • Subjection of air dry Dulux to elevated force dry temperatures without first adding Dulux Baking Reducer.


Always follow recommended procedures when reducing and applying successive coats of Dulux, and always add RK-5756 to 93 Line if film is to be force dried.

Finger prints showing

This blistered outline of finger prints shows what can happen when bare hands touch any surface about to be painted. No matter how clean the hands may seem, there is almost always some dirt, grease, oil, or perspiration which will cause blistering, rust, and poor adhesion. Keep bare hands off the surface!

In automobile plants, bodies are never directly touched with human hands after being chemically cleaned—the operators wear cotton gloves. It’s a good practice for ALL painters to follow!

Runs or sags


  • Too much thinner.
  • Too heavy coats.
  • Too wet coats.


  • Reduce material according to label directions.
  • Regulate fluid adjustment on spray gun
    (turn to right) to cut down flow of material.
  • Do not hold gun too close.

Pinholing in lacquers


  • Moisture in spray lines.
  • Trapped solvents.
  • Insufficient atomization or breaking up of material.


  • The drain valve of the air transformer should be opened daily to allow drainage of collected moisture. Remove and clean internal cleaning section of the older type transformers at regular intervals.
  • Do not apply materials too heavily but spray in uniform, normal coats to allow proper evaporation of solvents. Use recommended thinners.
  • Increase pressure of gun for proper atomization.
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