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.
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
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!
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.
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…
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/
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?
Thanks
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
Anyone got experience of vinyl wrap for aluminium boats?
Hi John, I ama new member with a Dutch built aluminium boat (Koopmans 46 cutter pilothouse shallow draft). Instead of spending lots of timeand money I am thinking of taking the topside hull paint off as after some 20 years some bubbles appear. And some scratches 🙂 . I have heard of icepellet blasting and the like. Any thoughts on that? Regards, Frederik
Hi Frederik,
I’m certainly an option. I’m a big fan of unpainted aluminium. However, first you want to check and see how fair the boat is underneath. A boat that old may have been built before computerized cutting of plate was common and in that case she may have a lot of plate irregularities that were then filled in with fairing compound prior to painting. So if you take all the paint off, you may end up with a boat that looks rather agricultural, rather than the smooth aluminium look of say a Boreal a boat that was built not to be painted. That could be a real negative for resale.
As to how to get the paint off, I’m don’t have any first hand experience but have heard that soda blasting is good. I have also heard that whatever the medium used, what is most important is the skill and care of the operator.
Hi John,
New here, thanks for the fantastic resource! I’m in the process of buying a 2002 Aluminium Reinke S11, and the paint on the deck is pretty worn (and the treadmaster peeling off). I was considering using KiwiGrip for non-skid and leaving the areas around the non-skid bare (as on for example https://bestevaer.com/fleet/models/bestevaer-49-zenith). Now my questions is, is this a good idea? Will the deck heat up unpleasantly in the sun in the unpainted areas? Will I create many more edges at which paint can start to peel/water get underneath? Would the same, but with treadmaster, be a better idea? Your advice would be much appreciated.
Best,
Alwin
Hi Alwin,
On the KiwiGrip I just don’t know since I have never used it and don’t know anyone who has used it on aluminium. That said, as long as you get the metal properly etched and primed there is no reason it should not stick and there is no question that it would be way less work and expense than Treadmaster.
And yes, bare aluminium will heat up pretty good in the sun, but then again, I can’t see that mattering much, particularly since I don’t believe in running around the deck without shoes on.
I guess if it were me I would talk to KiwiGrip and if they can come up with a viable system to get it to stick, go with that. The only exception would be if you are planning to be in places with a lot of snow. In that case treadmaster is the ulimate solution.
Put Treadmaster in the search box at the top of the site for several posts on our experience with it. Also it will be worth reading through the comments to those posts.
Just to report back on this – KiwiGrip can be applied wet-on-wet with epoxy, and that appears to have given pretty good results so far with regards to adhesion when wet-abrading the latter into the deck (although only time will tell!).
I did want to solicit your opinion on a partial paint failure we have experienced on our bottom paint. We have applied CopperCoat wet-on-wet on several layers of neat epoxy, as per manufacturer recommendations. We have had no issues with adhesion so far (with the boat on the hard for 6 months now), except just below the chain locker. Interestingly, there appears to be an area of corrosion that has caused the paint to peel, and this extends to above the painted area too. When viewing the flakes of epoxy, the layering of neat epoxy underneath the coppercoat appears to be intact.
My best guess is that we did not sufficiently remove salt residues from this area prior to painting (which would have experienced the highest concentrations as a result of runoff from the chain locker), as sodium chloride does have a strongly negative effect on epoxy adhesion. This would have caused an initial gap for the continued salt runoff to go into, resulting in an oxygen-starved environment with continued corrosion causing further peeling, etc.
However, this does not explain to me the presence of corrosion above the painted area. At a stretch, copper dust freed by the initial scuffing of the coppercoat might have settled there and caused corrosion in conjunction with the saltwater runoff. No areas exposed only to freshwater runoffs are showing adhesion issues.
I’ve attached a few pictures of the affected area. We have no concerns about the extent of the corrosion so far (it does not extend deeply into the metal whatsoever), but would of course like to avoid this continuing.
In short: do you think that “proper” surface preparation (grinding back of the affected area, thorough freshwater rinsing, degreasing, sanding, wet abrading of the initial coat of epoxy) will be sufficient to preventing this? We have a 20-year-old half-empty can of International etch primer, and seemingly no way to acquire more, so I can’t say I can think of another option anyway… Many thanks!
Edit: I appear to be struggling to upload images. Let me try a different browser…
Mcrosoft edge appears to be happier to upload than chrome for some reason
Hi Alwin,
I’m sorry, I really don’t know, but my guess would be just poor adhesion in the first place. I have only once tried to get epoxy to stick to aluminium without using an acid etch and abrading in and the bond only lasted a couple of years so I fear that without acid etch treatment reliable coating is going to be an ongoing problem.
I’m also not a fan of using copper coat on aluminium boats, even though the manufacture claims it’s fine: https://www.morganscloud.com/2007/01/01/coppercoat-antifouling-paint/