Pitting on Mast and Boom

[sandycohen]

Hi All -

I came across this thread

http://www.cruisersforum.com/forums/...ion-47874.html

looking for info on my pearson 32 (there are frustratingly few of them, so not much model specific info).

The picture the guy shows of his mast drew some comments about pitting.

My mast and boom are mostly in good shape, with continous paint. The keel stepped portion is not bad at all.

There are some spots between the deck and the boom (obviously I can't see much higher than that, but i know corrosion is usually worst closest to the water) that have pitting where the paint is gone - if i push on them with a screwdriver i can get metal to come off. There are other spots where the paint is 'bubbling' a little and it looks like perhaps pitting underneath.

What should I do to mitigate this pitting from spreading, and is it of major concern structurally? None of it seems to cause any cracks or other stress marks I can visually identify. Should I just sand around the pitting and paint the spots?

Thanks!

[Patrick_DeepPlaya]

My guess is that the spars were poorly prepped and the paint did not bond properly with the aluminum mast. Depending on your desired level of effort and want of beauty you could pull the spars, have them blasted, primed and painted or if you know what kind of paint it is you could do spot repairs.

I had the spars on my Pearson 424 prepped and painted with Alex Seal (Marine Paint, Primers & Fillers | Alexseal Yacht Coatings) Last year and thus far it's looking very nice. Aside from cleaning the spars of gear and filling holes with Belzona 1111 the yard did everything and it was not cheap, but for the aesthetics and the longevity of my spars I think it was well worth it.

-p

[hellosailor]

Sandy-
I'd suggest hitting the spots with dremel and wire brush (fast and effective) and then immediately putting on some aluminum primer followed by a touch of whatever top coat matches the existing color.
Eventually any 'paint' on aluminum will flake off but it takes a good long time and your mast/boom are not young. <G>

If you want a real solution, you can have the mast and boom stripped and then either repainted or anodized. Anodizing is equally effective but of course the finish is entirely different, and it can be a bit harder to find a shop that handles it.

Powder coating is another option, but I'd consider it less durable against things banging into it, never heard of a mast and boom being powder coated.

[roverhi]

Aluminum forms an oxide that protects it from further corrosion. Makes these nicks and scrapes self healing in the absence of electrolysis. Where the paint has bubbled, scrape the paint away so electrolite will no longer be trapped under the paint, remove loose corrosion and leave it. If you don't mind the mast looking real ugly, you can sand the mast to down to bright aluminum and painting with zinc chromate primer. That pretty much stops the corrosion but you'll have a greenish yellow spotted mast. You can have the mast repainted but that will just push the same problems a few years down the road. Repainting is also very expensive because of all the prep work involved cleaning the nooks and crannies in an aluminum mast.

Anodizing is the best solution but that's gotten very difficult to get done. Environmental regs have forced businesses out of the market on the west coast. Currently no tank big enough to handle a mast. Believe you can still get it done on the right coast but don't know where. Paint was a solution to the lack of anodizing facilities and cost of anodizing. Unfortunately, painting a mast is a headache that needs to be repeated regularly depending on use and location.

[Exile]

Originally Posted by roverhi

Aluminum forms an oxide that protects it from further corrosion. Makes these nicks and scrapes self healing in the absence of electrolysis. Where the paint has bubbled, scrape the paint away so electrolite will no longer be trapped under the paint, remove loose corrosion and leave it. If you don't mind the mast looking real ugly, you can sand the mast to down to bright aluminum and painting with zinc chromate primer. That pretty much stops the corrosion but you'll have a greenish yellow spotted mast. You can have the mast repainted but that will just push the same problems a few years down the road. Repainting is also very expensive because of all the prep work involved cleaning the nooks and crannies in an aluminum mast.

Anodizing is the best solution but that's gotten very difficult to get done. Environmental regs have forced businesses out of the market on the west coast. Currently no tank big enough to handle a mast. Believe you can still get it done on the right coast but don't know where. Paint was a solution to the lack of anodizing facilities and cost of anodizing. Unfortunately, painting a mast is a headache that needs to be repeated regularly depending on use and location.

Roverhi --

So are you saying it would be OK -- corrosion-wise -- to strip the mast paint down to bare aluminum and leave it that way (i.e. no ugly primer)? One could remove and then carefully reinstall all of the fittings & fasteners with Tefgel, for e.g., to prevent or at least mitigate further corrosion.

I am interested because I have a 64' mast that likely still has its original awlgrip paint (25 yrs.). It is bubbling around many SS fittings as one would expect, and the old paint leaves behind a powdery substance on limbs & clothes after climbing up it. I think it pretty obviously needs a paint job, but I shudder at the time it would take or the cost to have a yard do it. The spars need to come down this Fall in any event, so I'd be interested in any less costly alternatives.

Thanks!

[roverhi]

It would probably work just fine. My mast is unpainted and past it's 40th birthday. May have been silver anodized before it was born but that was a lifetime ago. I had a Series Land Rover habit for many years. There bodies are aluminum. I stripped one down to bare metal 20 years ago and it's doing just fine in Hawaii's salty corrosive atmosphere. Where the aluminum body is attached to the steel chassis, used soft top vinyl window material as an insulator from galvanic corrosion. Rover used aircraft aluminum alloy which is not very corrosion resistant, btw.

[Exile]

Very informative -- thank you. I would imagine the bare aluminum would be pretty shiny after you're done sanding the paint off, but would then get somewhat dulled down after not too long.

Would it be possible to post any pics of your boat? The Rover would be neat to see too!