1. Module 8: Painting GRP

2. Why is GRP so difficult to paint? Issue 1: Mould release agents In order to release GRP panels easily from their mould, a coating is usually applied to prior to lay- up. This mould release agent is completely incompatible with our paint systems, and MUST be fully removed prior to application of paint. Removal of mould release is best achieved using warm soapy water.

3. Why is GRP so difficult to paint? Issue 2: Air pockets PRP panels are inherently porous, and contain air air bubbles and pockets. Air pockets can be BIG! And they can be microscopic. Either way they can cause issues in painting.

4. Why is GRP so difficult to paint? Issue 2: Air pockets Large air pockets just under the surface expand during baking, and cause surface blisters. This can mean rework. The best way to overcome blistering like this is to bake the panel prior to painting. Use a temperature that is higher than that you will use to cure the paint, and bake for longer. For example, if you process at 60 o C for 30 minutes, pre-bake the panel at 90 o C for 45 minutes.

5. Why is GRP so difficult to paint? Issue 2: Air pockets Microscopic air pockets on the surface tend to cause a rough texture. They absorb paint, and act as a porous substrate causing poor appearance and low gloss. This is extremely noticeable if the GRP panel is next to a flat metal panel that has a good appearance and holds gloss well. This problem is best fixed by using a higher solids primer surfacer, and sanding. Extreme cases are fixed with putty, or by using a maxi- filler version of the primer surfacer.

6. Why is GRP so difficult to paint? Issue 3: Surface distortion GRP surfaces can be rippled and distorted. This can occur before painting, or during one of the baking cycles. The problem cannot be “cured” in the paint process, but can be fixed by using putty and high build primer systems.

7. Questions

8. End of Module 8