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.

See Also:

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