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.
prime the surface immediately after cleaning, as rust will set in if bare
metal is exposed too long.

Wrinkling of Dulux

Cause :

  • 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

Cause :

  • 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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