Cratering

Definition

Circular recesses with a diameter from 0,5 to 3 mm.  The problem may range in appearance from a very flat recess in the top-coat to a deep fault which extends back to the substrate.  If incorrectly repaired, the original craters may reappear as a more flat recess

Causes

Mainly: Oil, grease, wax and silicon residue.  (e.g. polishes containing silicon):

1] Humans - Marks from clothing, rubber gloves, skin and hair lotions.

2] Spray Booth - Lubricants from moving parts, release agents from plastic parts, hoses and sealants, inadequate oil and water trap bleeding, dirty ceiling and floor filters.

3] Paint Material - Incorrect use of paint additives (Anti-silicon additive), unsuitable thinner/hardener impurities from poor transportation or storage.

4] Workpiece - Residues from release agents (on plastic parts) slip additives, solder flux, bitumen and oil from insulating mats.

5] Paint processing ancilliarie - Release agents from new sponges, unsuitable cleaning agents or abrasives, adhesives from tapes.

6] Environment - Intake of polluted air from other work areas (polishes, oil sprays, release agents, fine dusts etc) sealant and insulation dusts from the building.

How to avoid

Points 1 to 6 give the reasons for many of the causes of cratering in paint finishes, from which it is possible to take precautions to avoid the the contamination. In principle, we would recommend that only silicon–free products are used in the vicinity of the paintshop, and substrates are always cleaned thoroughly.

Repair

Thoroughly sand the paint build back to a sound substrate. Repaint using the correct choice of primers and top-coats. If it is necessary to repaint over a paint layer where silicon induced craters are clearly present, we recommend the use of Glasurit Anti-Silicon Additive 580-100 to be applied.