Painting the boom

dmairspotter · Post by **dmairspotter** » Mon Oct 13, 2008 6:41 pm

I am painting my Alu boom. Its stripped of all hardware, and sanded down the the gold anodizing (some places through the anodizing).

I'll be painting by hand, and it ain't to warm up heah.

Who has had good luck with what products?

I'll be painting it white.

TIA

CharlieJ · Post by **CharlieJ** » Mon Oct 13, 2008 6:56 pm

I've had good usage from a zinc chromate primer , then a polyurethane top coat. Did one mast that is still looking good 8 years later. And that's sailing salt water.

dmairspotter · Post by **dmairspotter** » Tue Oct 14, 2008 8:46 am

Thanks Charlie.

Did you take off all the anodizing? Did you spray or brush?

CharlieJ · Post by **CharlieJ** » Tue Oct 14, 2008 9:15 am

only took off what I had to to get a smooth surface and used a spray gun.

Finished with 220, wiped with acetone and IMMEDIATELY shot the primer. You can't wait a day- otherwise the bare aluminum will oxidize again.

Then I sprayed the finish coats

Shoalcove · Post by **Shoalcove** » Tue Oct 14, 2008 9:01 pm

I did mine last spring. Sanded where needed, zinc cromate, appropriate primer and Perfection 2 part paint. Used a brush. Looks great! A good time to replace dodgy fittings and fasteners. Good luck, David

dmairspotter · Post by **dmairspotter** » Tue Nov 04, 2008 11:13 am

Okay, today was the day.

Resanded the boom, then shot the Zinc Chromate primer out of a spray can. Instructions on the can are useless, so a few questions.

The primer is translucent yellow after one coat. Is that all I need or should I shoot another coat to get more build?

After it dries, do I sand the zinc chromate, wipe it with acetone, or just start overcoating.

Do I need another primer under between the zinc chromate and the topcoat(s)? I'm using Brightside one part.

Thanks for the help.

Post by **Tim** » Tue Nov 04, 2008 1:11 pm

Depending on the exact type of zinc chromate primer, the surface may remain translucent after application. The key is good coverage in all areas, not the thickness.

You should be able to apply topcoat right over the zinc as soon as it is dry. Sanding the thin zinc chromate primer will likely go through, thereby eliminating the primer's effectiveness. Ususlly there is an overcoat timeframe--you can't overcoat before X amount of time has elapsed (2 hours for Awlgrip 30-Y-94 zinc chromate, for example) and have to overcoat before Y amount of time (24 hours for the 30-Y-94). Your spray can is likely different, but I'd suggest similar time frames would work.

This is my boom coated with Awlgrip's primer.

dmairspotter · Post by **dmairspotter** » Tue Nov 04, 2008 2:02 pm

Thanks Tim

Quetzalsailor · Post by **Quetzalsailor** » Wed Nov 05, 2008 10:35 am

Gorgeous! Jealous!

3 years ago, I brush-applied the zinc-chromate primer to the bare spots on our aluminum spi pole. It is a LeComte made spar with rather sloppy welded tapers and was originally epoxy painted, not anodized; it had been repainted at least once since 1970. I then brush applied Brightside Polyurethane for finish. I wet-sanded initially, and between coats. It looks lousy! And it's prone to damage and chipping.

Last spring, I did much the same with the mast. Similar construction, it's a rolled shape, not extruded, and it still had much of the original epoxy paint under subsequent paint. I wetsanded between coats, and used Primocon for primer which is, according to Cortraulds (the maker), absolutely the wrong stuff. I used Brightside Polyurethane for finish. Contrary to Cortraulds' dire prediction, the finish did not fail to cure, and has not fallen off after 1 season. However, the genny halyard has beaten the new finish off where it slaps on the upper half of the mast so it is beginning to look as bad as it did before.

Won't be this year, but the boom is up for refinishing, too.

So! What finish is really adequate? Good old anodizing, I think, does better than anything but after only 20-30 years, it fades and abrades. The paint is vulnerable to impact damage since it's brittle. But the whole idea of dismasting and repainting is pretty trying; we Middle Atlanticers don't pull the rig every year like you New Englanders.

One thought I had was to apply clear tape, like for automobile rocker panels, on chronically vulnerable places. Another though was to apply raised pads along the mast where the genny halyard slap.

David · Post by **David** » Wed Nov 05, 2008 11:37 am

The clear bra sounds like a great idea! I'm curious why you didn't use the manufacturer's primer for Brightsides instead of Primocon?

Quetzalsailor · Post by **Quetzalsailor** » Wed Nov 05, 2008 2:17 pm

Ahhh. Uhhh.

There's a long string about this adventure on this site back in the Spring.

Basically one weekend, I read the instructions on the cans and saw that the same thinner was sold for use with the Primocon and the Brightside. Thus I decided that there would be little problem with incompatibility using a convenient spray can of primer for quick touch-up versus the inconvenience of using the two-part zinc-chromate. So I did. Then I came back to the office and began researching and emailing.

Much to the Cortraulds guy's surprise, I seem to have gotten away with it. But don't do it!

David · Post by **David** » Wed Nov 05, 2008 2:26 pm

Ok i see. And is Cortraulds part of Interlux or vice versa? Frankly I have found Primicon to be a very nice primer. I used it over an epoxy barrier coat and on my prop.