FRP Hull Painting (above and below waterline)

For the resurfacing, clean and degrease the surface very well with liquid rinse. Rinse well afterwards with clean tap water. All old wax residues have to be removed completely. Grind the whole surface with sanding paper grit P150-180 and dust-off and clean with clean cloths. The gelcoat has to be very well sanded, and the surface should be cleaned and well dried. 

Painting system can be coated with two different parts: above and below waterline. The whole painting processes are shown in Fig 1.

[Fig 1. Hull painting process]

For the above waterline, there are two steps, under coating and top coating, and multi-coats are coated in each step (C. Nigel, 2006). Thickness and over-coat interval of each coat is important factor to get expected results it depends on products. In each coat, paint should be well prepared; base should be stirred to lift up heavy settlements then mixed with agent together by product’s instruction (C. Nigel, 2006).

In under coating, it coated on the resurfaced layer with two coats. Undercoat might be slightly sanded for the top coat for each coat. It has tolerance for water, fuel and chemicals however, it is not suitable to apply below waterline. Minor filling and fairing can be done with 400 grit sandpaper for each coat. For the International^® products, Perfection Undercoat^® is recommended with 75 µ WFT for each coat of at least two coats by (C. Nigel, 2006).

In top coating, high performance top coat which is polyurethane can be used to get advantages. Its gloss has twice longer than conventional top coat. Especially, it has tolerance for dark area and heat, water, fuel and oil. However, it is difficult to apply since the high performance coat has shorter wet edge times. Top coat can be processed as the undercoat, it requires clean and gloss finishes. For the International^® products, Interlux super ^® is recommended with 85 µ WFT for each coat of two or more coats by (C. Nigel, 2006).

For the below waterline, high performance epoxy coating system is applied to protect surface from the moisture, oxygen, oil and fuel. Therefore the system can be expected good results in any application especially for the below waterline. To apply epoxy system, the surface should be cleaned and dried with atmospheric condition. For the International^® products, Metallic Primocon3^® is recommended with 120 µ WFT for each coat of 4-5 coats by (C. Nigel, 2006). Epoxy filler can be used for filling and fairing surface after each coat.

The next step is applying antifouling tie coat which is only one coat. To apply the antifouling, mask along the waterline and covered the above waterline with plastic. Antifouling coat is usually applied at least two coats, third coat can be applied to the rudder and alone waterline to protect the wear-out by wave (C. Nigel, 2006). For the international product, International^® Intershield 163 Inerta 160^® and Interswift 655^® can be coated (International_W, nd).