Painting Aluminum Boats

zinc chromate yellow

Zinc Chromate is usually yellow and sometimes green depending on formulation, to get other colors such as red or gray a pigment must be added.

You may be thinking of buying or selling an aluminum boat that needs some cosmetic updates, or perhaps you’re simply trying to improve the appearance of the aluminum boat you already have—the best solution may be to repaint that aluminum boat. In the years that I worked at a local boatyard the paint crew painted only a few aluminum boats–fiberglass being the more prevalent hull material at this salt water yard. Those aluminum boats we did paint required a slightly different approach due to the oxidizing nature of aluminum.

zinc chromate spray

You can buy zinc chromate primer in spray cans for priming outboard and I/O engines lower units.

We still had to create a mechanical bond for the paint by either sanding or sand blasting the hull to remove all the old paint, followed by tacking off the dust and debris with a wax and grease remover. We hired a sand blasting specialist when needed, and I’d recommend the same for anyone contemplating sand blasting aluminum. I believe that sand blasting aluminum is a much more delicate operation than fiberglass and not a chore for a do-it-yourselfer. We avoided the chemical etchers commonly used to create the mechanical bond because of the toxicity, and stayed away from soda blasting or chemical peels because they didn’t give as good a mechanical bond—for the most part we simply sanded off the old paint.  As I’ve heard it said, painting an aluminum boat is not like painting the ceiling of the Sistine Chapel. However, once the hull was clean and free of the old paint, the biggest difference between painting an aluminum boat and any other boat is the special primer needed for aluminum boats.

Untreated aluminum hulls can pit and deteriorate over time and require protection from oxidation. The airline industry learned how to protect aluminum planes from oxidation during World War II by priming the surfaces with zinc chromate. The yellowish-green primer, developed by the Ford Motor Company in the 1920s, not only protects against oxidation but acts as a good tie-coat for almost any finish coat you choose, whether it be a Teflon based fresh water bottom paint like Interlux’s VC-17 or a specific metal bottom paint like Trilux 33 or even two-part epoxy paints used for topsides and available at marine supply stores such as West Marine. The use of this primer clearly affects the appearance and longevity of the paint jobs.

For the folks who like that plain aluminum look on their boats, sans paint, I recommend Aluma Guard to clean, polish and protect bare aluminum. We used this product extensively for cleaning and treating aluminum spars. I hope this helps with improving, maintaining and protecting the look of your aluminum boat.

 

Comments

  1. Dennis Bourgoin says:

    In the state of Maine zinc chromate is out-lawed.So what would I use to replace it . I have a 1957 Cadillaic Custom that I want to repaint. Any info would be a great help.

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