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Peeling Paint on the Portlights

Practical Sailor Advisor

Peeling Paint on the Portlights Our 5" x 12" aluminum Bomar portlights, retrofitted to our 1978 Valiant 40 in 1987, are losing their paint, which is peeling. We don't want to remove the eight portlights (which cost about $200 each) because none of them leak...and that's important. They were installed with polysulphide, which has great adhesiveness. Removing the portlights would ruin them. Can we remove the paint, or should we just sand them and repaint?

Ralph Harding Pt. Richmond, California

If you could remove the portlights, you could have the frames sandblasted and powder coated. One of our readers reported thathehadfive cleats done by the Rapid Finishing Co. (43 Simon St., Nashua, NH 03060, 603/ 889-4234) for $85.

If you really don't want to remove the portlights, you can sand them smooth (you needn't remove all the paint) and recoat them. Whatever paint you use, we'd test a tiny spot to make sure nothing chemical happens between the old and new paint.

Bomar's Ken Randby said portlights of that vintage were spray-painted with two-part polyurethane (A wlgripB). Wet spraying is becoming obsolete mostly because ofstringent OSHA and EPA regulations. Randby said Bomar has shifted to powder coating, which is both cheaper and better. Randby said powder-coating does not peel, if properly done.

Although powder coatinghas been viewed by some critics as a process prone to peeling problems, Randby said the fast-growing industry is rapidly peqfecting the technique.

Bomar's painting expert, Steve Belletsky, said that powder coating is like varnishing in that the prepara- tion of the suqface and cleanliness is vital. Bomar uses a zinc chromate bath before a piece is placed on a negatively-charged conveyor belt and run past a spray gun that fires positively charged dry paint particles. Every bit of the powder, which costs only about $2.50 a pound, is drawn to the pieces being coated. In fact, the electro-magnetic charge lasts for up to 12 hours. He explained that some suqface impeqfections can be covered by a thicker (up to 20 mils) powder coating, but thatgenerallya thin coat (4 to 5 mils) better resists chipping.

The pieces, covered by the dry powder held loosely and evenly in place by magnetism, then go into an oven. The oven heat, at about 400 degrees, melts the powder and completes the job.

Belletsky said a wet sprayed sur- face can be glass smooth, but powder coatinghasa detectable "orangepeel" appearance. He added, however, that there is now on the market a new powder paint that is self-leveling. He said Bomar is trying it now, both with and without the zinc chromate bath, to see howitpeqforms in saltwater. He said that, in his opinion, powder coating is going to become more and more , J common. He said even plastics and wood can be powder-coated.

For aluminum, powder coating, if not subjected to severe abrasion, has about the same longevity as anodizing. However, for aluminum masts, for which painting seems to have replaced anodizing, powder coating will be difficult because of the need to "bake" the powder.

Belletsky cited a recent issue of an industry magazine that said that auto makers like General Motors are converting to powder-coating.