Design & DIY

Cottage Q&A: Best paint for an aluminum boat

Several old aluminum boats lined up at a dock By HenriqueWestin/Shutterstock

I want to paint the bottom of my aluminum boat. The original paint is chipping off. I was going to use a spray-paint primer, but I’m concerned about the environment. Is there another approach? And after the colour, do I need a clear topcoat?—Mel David, via email

While nobody’s going to argue that spray paint is good for the environment—it does release volatile organic compounds—it’s at least not as bad as it used to be. Today’s spray paints no longer contain chlorofluorocarbon propellants. (Countries began banning those in 1978.)

A spray-paint primer is convenient, but if you don’t want to use one, don’t. Brad Schmidt, a specialist with the Yacht Division of AkzoNobel, suggests a thinned-down epoxy primer instead. You can apply it with a brush or a roller; a thinner formula “will allow the primer to get into all the nooks and crannies” of the boat. Follow with a multi-purpose epoxy primer before you put on your colour; use a marine-grade polyurethane paint.

None of our experts thought that you’ll need a clear coat overtop. But everyone emphasized—repeatedly—how important prep is going to be. “Painting aluminum is always tricky,” says Schmidt. “It’s a different beast.”

Five painting tips that our experts swear by

Sanding properly is key—you need to remove every bit of that old, chipping paint. “Everything needs to be sanded down,” says Ryan Mack, the owner of Northern Lakes Boat Works in Gravenhurst, Ont. “You can’t bond to bad paint.” 

Shop around for the right products first. Plenty of companies have coatings for marine applications, says Gary Wedemeyer, a product specialist with the Automotive/Marine Aftermarket Division of 3M. It’s easy to find info on application procedures on their websites, so you can investigate before you buy. “I have personally applied a high-quality marine-grade exterior enamel to the bottom of a 12-foot aluminum boat using a brush and roller,” says Wedemeyer. “I cleaned and scuffed the surface according to the paint company’s recommendations, and I didn’t topcoat it.” A few years later? His tinny is still looking great.

Happy painting! Or, uh, cleaning, cleaning again; sanding, more sanding; priming a bunch…then painting. 

This article was originally published in the October 2021 issue of Cottage Life magazine.

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