Mast paint yes/no?

[jtsailjt]

I have a friend who just bought a boat with an aluminum painted mast. There is some bubbling of paint around some of the fittings but overall the mast looks great and the step and bottom of the mast are fine. The quote he got to remove all the mast hardware and repaint is a good deal higher than he wants to spend. I've never liked the idea of painting aluminum because it always seems to have problems with adhesion or eventually water gets behind it in places (around fittings) and is held in place by the paint so corrosion/bubbling occurs.

So, would it be acceptable for him to have his mast sand blasted with the hardware in place and just leave it as bare aluminum or would doing that invite further corrosion? Does aluminum need to be protected by anodizing or painting or is it OK to leave it bare? I've always had masts that were bare or anodized aluminum and have never had any problems with them. Other than for aesthetics, is there any reason to paint an aluminum mast?

[slug]

Originally Posted by jtsailjt

I have a friend who just bought a boat with an aluminum painted mast. There is some bubbling of paint around some of the fittings but overall the mast looks great and the step and bottom of the mast are fine. The quote he got to remove all the mast hardware and repaint is a good deal higher than he wants to spend. I've never liked the idea of painting aluminum because it always seems to have problems with adhesion or eventually water gets behind it in places (around fittings) and is held in place by the paint so corrosion/bubbling occurs.

So, would it be acceptable for him to have his mast sand blasted with the hardware in place and just leave it as bare aluminum or would doing that invite further corrosion? Does aluminum need to be protected by anodizing or painting or is it OK to leave it bare? I've always had masts that were bare or anodized aluminum and have never had any problems with them. Other than for aesthetics, is there any reason to paint an aluminum mast?

Paint is for appearance...also....when sails touch a naked oxidized alum mast they turn black

On race boats alu masts were always naked...but several times a year they got pulled and polished

Sand blasting with hardware still fitted sounds like a stupid idea

[rbk]

Unpainted or un-anodized aluminium will corrode in the presence of salt. Deep pitting can occur. On the cheap its best to pull the fittings, sand back the flaking/bubbling and repaint/touch-up. If and when it gets really bad the whole thing will have to be stripped and painted. The problem comes from the mast being stripped and painted then drilling holes to mount hardware. This tends to crack and lift a small portion of paint. Then the water gets in and the bubbling occurs. When re-installing hardware ensure they are properly bedded and dissimilar metals are isolated.

[slug]

Originally Posted by rbk

Unpainted or un-anodized aluminium will corrode in the presence of salt. Deep pitting can occur. On the cheap its best to pull the fittings, sand back the flaking/bubbling and repaint/touch-up. If and when it gets really bad the whole thing will have to be stripped and painted. The problem comes from the mast being stripped and painted then drilling holes to mount hardware. This tends to crack and lift a small portion of paint. Then the water gets in and the bubbling occurs. When re-installing hardware ensure they are properly bedded and dissimilar metals are isolated.

Sounds correct for a boat that will be put to sea

Small coastal craft seem to hold up well naked

And with fittings ...for max corrosion protection isolate the dissimilar metals then bed with Sika or 3m to make the joint water proof

[Cheechako]

I vote unpainted for sure. I had my big mast repainted, the full meal deal, very expensive. Within a year and a half of cruising it was bubbling, pitting on the lower 6 ft or so anyway.
Some masts have a bunch of filled spots in the metal to make them look good before painting though!
Another option is sand bare for the lower portion... 8 feet or to the spreaders...

[tkeithlu]

With due respect for the problem of blackened sailcloth, paint has shown itself in the posts above to be a really good way to start and hide corrosion. It serves the same purpose over cracks.....

Your mast is a critical structure, and they do fail. I imagine racing masts (slug, above) are left bare so they can be inspected. A polished mast doesn't have aluminum oxide there to mar your sail, but that is a maintenance problem. I think the summary advice is, if you don't have to paint it, don't.

[Don C L]

My 60 year old mast has never been painted and is fine.

[SVTatia]

Originally Posted by jtsailjt

...So, would it be acceptable for him to have his mast sand blasted with the hardware in place and just leave it as bare aluminum or would doing that invite further corrosion? Does aluminum need to be protected by anodizing or painting or is it OK to leave it bare? I've always had masts that were bare or anodized aluminum and have never had any problems with them. Other than for aesthetics, is there any reason to paint an aluminum mast?

The question here is whether to touch up the paint or strip.
If starting over leave unpainted but once painted, its a major pain to remove.

His options are to send and repaint or touch up for ever. If repainted, will still need to touch up in the future....

I'd opt for touching up, paying attention to the surface prep by etching, etc.

[rbk]

Most ‘bare’ masts people have are almost always anodized. If it’s not there’s a good chance it’s got a lot of flaky white residue l over it (oxidization). The problem with that is the oxidization layer is uneven and can be rubbed or scrapped off exposing bare aluminum to salts causing pitting which can lead to failure.

[rbk]

Originally Posted by tkeithlu

With due respect for the problem of blackened sailcloth, paint has shown itself in the posts above to be a really good way to start and hide corrosion. It serves the same purpose over cracks.....

Your mast is a critical structure, and they do fail. I imagine racing masts (slug, above) are left bare so they can be inspected. A polished mast doesn't have aluminum oxide there to mar your sail, but that is a maintenance problem. I think the summary advice is, if you don't have to paint it, don't.

The bubbling generally isn’t corrosion but oxidization although sometimes when dissimilar metals are in contact the bubbling paint can be corrosion or when salt makes its way behind the paint.

[Cheechako]

Originally Posted by rbk

Most ‘bare’ masts people have are almost always anodized. If it’s not there’s a good chance it’s got a lot of flaky white residue l over it (oxidization). The problem with that is the oxidization layer is uneven and can be rubbed or scrapped off exposing bare aluminum to salts causing pitting which can lead to failure.

There are a ton of bare masts out there, especially on smaller boats. Few are anodized, but some are for sure.

[Cheechako]

Originally Posted by jtsailjt

I have a friend who just bought a boat with an aluminum painted mast. There is some bubbling of paint around some of the fittings but overall the mast looks great and the step and bottom of the mast are fine. The quote he got to remove all the mast hardware and repaint is a good deal higher than he wants to spend. I've never liked the idea of painting aluminum because it always seems to have problems with adhesion or eventually water gets behind it in places (around fittings) and is held in place by the paint so corrosion/bubbling occurs.

So, would it be acceptable for him to have his mast sand blasted with the hardware in place and just leave it as bare aluminum or would doing that invite further corrosion? Does aluminum need to be protected by anodizing or painting or is it OK to leave it bare? I've always had masts that were bare or anodized aluminum and have never had any problems with them. Other than for aesthetics, is there any reason to paint an aluminum mast?

Remove the hardware. Rebed the hardware with a product that inhibits corrosion. Lanolin, or the products sold for that purpose. You dont need to blast though. A good sanding with orbital sander should be fine. It's often just easier to sand enough to paint than to sand all the way, which is why people continue to paint. I would not recommend trying to sand the entire mast.
The corrosion comes from dissimilar metals, combine splashing salt water with that and it's pretty aggressive. The cleats, winches, gooseneck etc are often SS or Bronze.

Anodizing is great, but few places have tanks long enough to do it. No big boat masts that I know of are anodized due to that. Almost all big boat masts are joined in the middle by welding or sleeves and riveting due to extrusion length availability.

[SVTatia]

Originally Posted by Cheechako

There are a ton of bare masts out there, especially on smaller boats. Few are anodized, but some are for sure.

Yes most for large boats are/were anodized, and back a couple of decades ago some were sold painted since the manufacturer did not have or could not have such a long tank. These masts are still around.

[noelex 77]

Aluminium masts are made from extruded and preferably very stiff aluminium. Unfortunately, the aluminium grades that meet these requirements are not the most corrosion resistant. A typical mast has a great deal of attached stainless steel creating dissimilar metal corrosion problems and exacerbating these issues.

In terms of corrosion/ maintenance, painted is the worst option. The best surface finish is anodised, but bare aluminium will generally have less maintenance and fewer problems than painted aluminium. Unfortunately, bare aluminium is not a great cosmetic match for many modern boats.

[jtsailjt]

Originally Posted by noelex 77

Aluminium masts are made from extruded and preferably very stiff aluminium. Unfortunately, the aluminium grades that meet these requirements are not the most corrosion resistant. A typical mast has a great deal of attached stainless steel creating dissimilar metal corrosion problems and exacerbating these issues.

In terms of corrosion/ maintenance, painted is the worst option. The best surface finish is anodised, but bare aluminium will generally have less maintenance and fewer problems than painted aluminium. Unfortunately, bare aluminium is not a great cosmetic match for many modern boats.

That pretty well sums up what I've been thinking too. It would be nice if it were anodized but putting paint on it seems to me the worst thing to do because when (salty) moisture finds its way in through any small imperfection or crack in the paint, the paint holds it there against the aluminum where an unpainted mast gets almost of the salt removed every time it rains and then dries off shortly after the sun comes out. Also, since the mast is full of holes filled by stainless steel fasteners, and that's where the tiny paint cracks tend to occur, it becomes a perfect recipe for corroding the aluminum near the stainless fittings and bubbling the nearby paint. As has been pointed out, an unpainted, unanodized mast, especially the lower 10' or so, will have frequent exposure to salt spray so some pitting is likely, but maybe this is the lesser of two evils?

I agree aesthetics is an issue because a painted white mast/boom does look very clean and neat compared with a somewhat oxidized aluminum mast, but it seems to me that the cost of maintaining that paint is just too much. So, I think my suggestion will be to take the fittings off the mast (or maybe just the fittings that show signs of corrosion around them?), sand or sand blast all the paint off, and then replace the hardware while attempting to isolate the dissimilar metals in the fittings and fasteners to the maximum extent possible.

Of course it's ultimately up to my friend since it's his boat but he asked for my advice and I wanted to make sure we looked at the problem from all sides so all the input above is appreciated. I will pass on all your thoughts as well as my own and he should be able to make a pretty well informed decision.