How To Troubleshoot Automotive Paint: Causes and Cures

Poor adhesion

Cause:

  • Improper preparation of surface.
  • Wrong undercoats.

Cure:

  • Thoroughly clean the old finish with Prep-Sol to remove grease, wax, polish, and other foreign matter. Improper treatment of bare metal surfaces also causes poor adhesion.
  • Follow “Procedures” and label directions.

Chalking of lacquers

The left section of this panel, which was exposed on a paint farm, shows (in comparison with an unexposed section on right) what happens when a finish chalks. A natural failure, chalking is the gradual breaking up of the film under weathering and exposure to the sun’s rays. It results in a gradual loss of gloss and powdering of the surface.

When this condition is encountered, rub and polish the surface to remove “dead” pigments and get to the “live” film beneath. Then wax the finish to protect and prolong its life. The use of a mist coat mixed with a slower-drying thinner on a finishing job will enable the film to set better and aid in retarding chalking.

Rough, dirty finish

Cause:

  • Applying finish over dusty surface.
  • Dirty and dusty shop or spray booth conditions.

Cure:

  • “Tack-wipe” the surface immediately before spraying color coats in order to remove dust and dirt. Tack rags were a regular part of finishing equipment in the old days when varnish was used. Now with synthetics it’s a habit to be cultivated again. Get in the tack rag habit. They cost little—and save a lot of headaches.
  • Good housekeeping.

Lifting

This condition results from applying lacquer type products over unaged air dry synthetic finishes. It also results from applying a finish over a surface from which old wax, grease, or polish is not thoroughly removed. To avoid the latter, always clean the old surface with Prep-Sol to remove wax, grease, polish, and other foreign matter before any sanding is done. Improper recoat time may also cause lifting.

Shrinking and splitting of putty

Cause:

Because putties usually dry quickly, they may shrink, split, and remain soft when applied too heavily, as shown by this close-up.

Cure:

Apply several light coats with a glazing knife or squeegee, allow to dry between coats.

Wet spots

If you apply finish over a waxed surface you encounter a difficulty as illustrated on the panel shown here—in this case wet spots which spoil the job. To avoid this, use Prep-Sol as a cleaning agent to remove wax, grease, and polish from the old surface.

Crazing, cracking, and checking

Cause:
These conditions, each a degree of the other, result when:

  • Topcoats are applied before the undercoats are dry.
  • Too heavy coats are applied, resulting in non-uniform drying throughout film.
  • New finish is applied over excessively built-up, aged. and cracked old finish.

Cure:

  • Always let undercoats dry thoroughly before spraying color coats. Weather conditions will alter drying time—so do not follow a standard time.
  • Do not “pile” on coats.
  • If old finish is made up of an excessive number of coats and/or if cracking of the old finish is in evidence, remove the old finish completely before refinishing.
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