Q&A: What Should I Paint On My New Aluminum Boat?

Question: You say you would not paint aluminum. Ok, it is hideously expensive (I have been quoted £10,000 just for materials), it is difficult to key, and we have been advised to sand blast and paint the same day (tricky!). So, if you were to start all over again with a newly built boat, what parts would you paint?

Answer: You are right, painting an aluminum boat is incredibly expensive and if you get someone else to do it the materials price you were quoted will be less than half of the final cost.

Yes, you must key the aluminum, but there is much more to it than that. You also need to acid wash and get a good zinc chromate primer on that day (this goes under the normal high build primer). Don’t believe anyone who tells you that acid etching and metal primers are not necessary. Even some professional painters will try and tell you this because they don’t want to deal with these nasty chemicals. If you don’t etch and prime properly, all your expensive paint will start bubbling in a couple of years. By the way, the same applies to painting aluminum spars.

The only part of a new aluminum boat I would paint is the bottom. Starting with a primer as discussed above, followed by a good barrier coat (we use InterProtect from Interlux) and topped off with an aluminum-friendly anti-fouling (we use E-Paint ZO).

Definitely do not paint the bilge. You will never get the paint to stick properly and you will then have to live with loose paint chips in the bilge with the potential to block bilge pumps, block limber holes and gather in wet clumps with any dirt. This will actually promote corrosion rather than prevent it.

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Meet the Author

John Harries

John was born and brought up in Bermuda and started sailing as a child, racing locally and offshore before turning to cruising. He has sailed over 100,000 miles, most of it on his McCurdy & Rhodes 56, Morgan's Cloud, including eight ocean races to Bermuda, culminating in winning his class twice in the Newport Bermuda Race. He has skippered a series of voyages in the North Atlantic, the majority of which have been to the high latitudes. John has been helping others go voyaging by sharing his experience for twenty years, first in yachting magazines and, for the last 12 years, as co-editor/publisher of AAC.

7 comments… add one
  • pete October 11, 2010, 5:04 pm

    We have a friend here in Morlaix that bought a small alu yacht that was well tatty. We sprayed a special etching primer for alu then 2 coats of undercoat and then 8 coats of polyurethene gloss single pack. It has kept well and can be repaired with a little rubbing of wet and dry and a touchup of the original paint

  • Taras January 25, 2016, 5:39 am

    Hello John!
    I have an old aluminum mast (on aluminum boat) that was painted couple of times but now the paint is coming off.
    What do you think about stripping off the paint from the mast and leaving it unpainted? Are there any drawbacks to this? (I don’t care about the look)
    Thank you!

    • John Harries January 25, 2016, 7:49 am

      Hi Taras,

      I think that would probably work fine. I know someone who did exactly that some years ago, and as far as I know all is good.

      Some will tell you that this course of action will be a problem because either there won’t be any anodizing on the mast, or if there was, it will have been compromised by the painting process; however, I don’t think that’s right. After all, unpainted aluminium boats are not anodized.

      One challenge will be how to get the the paint off. If you use chemicals you need to make sure they won’t attack to aluminium. Also, using steel tools to scrape is probably not a good idea, although stainless steel is probably alright. You might want to look into soda blasting.

      I’m guessing that you will need to remove all of the fittings to do this, so now would be a good time to make sure they are all properly isolated with plastic spacers and the fastenings liberally coated with either Duralac or Tefgel. Here’s a chapter from Colin that will help.

  • Robert McArthur January 16, 2020, 6:52 pm

    When you say “don’t paint the bilge”, what would you do then in the engine room/bay? We’d like to see any leaks (or dropped coins!), yet the bare alu is, and will continue to be, covered by the barrier that forms on alu; let alone the small pits et al. that have formed over the last 20 years. We were thinking of sanding/grinding/prepping/painting the engine room bilge, but your comment has me questioning…

    • John Harries January 16, 2020, 8:00 pm

      Hi Robert,

      I stick by my recommendation…DON’T PAINT. Oops, sorry I’m shouting. There is no benefit to paining aluminium and many downsides. You will never get the paint to stick properly in the bilge, so by painting you’re just buying yourself a problem for the future. And don’t worry about a dropped coin, it won’t do any damage. Much more on caring for aluminium boats here: https://www.morganscloud.com/2017/11/11/22-aluminum-boat-care-tips-part-1/

      • Robert McArthur January 18, 2020, 5:34 am

        Ok – I hear :).
        Any ideas on how to clean out the bilge around/under the engine so we can see problems/leaks more easily given shes oxidised and pitted a bit? Is it the usual grind and sand?
        Also, have you or anyone tried using Cerakote over alu?


        • John Harries January 18, 2020, 11:42 am

          Hi Robert,

          Just give them a good scrub, that’s all that required. As to cerakote I have no experience, but the bottom line remains the same, there is no benefit to coating aluminium and a lot of downsides. The key thing to understand is that if aluminium is wasting then all coating does is hide the problem. The correct solution is to find the core problem, usually stray current, sometimes more noble metals in contact. As to oxidization, that’s a good thing, not something to be cleaned off. And if the plate is compromised badly then the only think to do is cut it out and replace it, there are no short cuts. That said, a bit of pitting, as long as it’s not deeper than say 1mm is not a problem.

          I know how tempting it is to want to make all this clean and shiny (I have made that mistake myself in the past) but don’t do it.

          A good soap to use the clean the bilge is one of the ones formulated to clean aluminium airplanes. Pretty aggressive, but won’t hurt aluminium. Give these guys a call and they will sell you some: https://www.aircraftspruce.com

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