Pinholing

Description

Small cavities, generally less than 1mm in diameter, occurring over stopper, filler or GRP substrate.

Cause

Absorption of the paint into holes in the substrate. This is due to:

1. Air inclusions in GRP resin.
2. Inadequate preparation and sealing of the substrate.
3. Poor quality filler or stopper.
4. Poor mixing of filler, poor application of filler or stopper

Prevention

1. Heat to above spraying temperature prior to preparation to burst inclusions. Do not heat above 80°C to avoid distortion of the surface.
2. Inspect GRP surfaces and filled or stopped areas carefully. Stop any pinholes, spot prime and flat until smooth before priming the complete surface.
3. Use only recommended materials.
4. Mix filler correctly, apply filler and stopper in thin, smooth layers. Allow to harden fully before applying further layers and before rubbing down.

Rectification

Rub down the affected area to the primer, stop any pinholes, spot prime and flatten until the surface is smooth, then repaint.