Aluminium Corrosion Repair

[isurus]

I discovered a few areas behind a vinal trim on my BC560 which must have held salt while in storage. The areas are quite heavily corroded and will need to be repainted.

Is there any special type product to nuetralise the corrosion, or should I just sand back the area, prepsol and etch prime before painting?

Cheers

Brad

[tuffy]

Brad, just sand back to bare ally and etch prime after cleaning. Be careful using Prepsol if you are going to paint in 2pack. some 2 pack paints can react to Prepsol and cause the paint & primer to lift which can create bubbles into which the salt can get.

I was told this by the paint manufacturer AFTER I painted my boat which we cleaned with Prepsol. This doesn't apply if you are just using single pack marine paint.

Hope this helps.

Cheers, Russ.

[isurus]

Brad, just sand back to bare ally and etch prime after cleaning. Be careful using Prepsol if you are going to paint in 2pack. some 2 pack paints can react to Prepsol and cause the paint & primer to lift which can create bubbles into which the salt can get.

I was told this by the paint manufacturer AFTER I painted my boat which we cleaned with Prepsol. This doesn't apply if you are just using single pack marine paint.

Hope this helps.

Cheers, Russ.

Thanks Russ,

I had a similar problem when I touched up my outboard skeg fin. In a few spots the paint didn't stick so well. I thought that maybe the emory paper I used to sand it back may have had silicon in it. Looking at what you have said it might have been the prepsol......

Brad

[volitans]

you know, this is why I tell my mates this website is worth it's weight in gold.

My Quinnie 5m Reef Runner has wide gunnels which are showing heaps of aluminium corrosion. Luckily that's the only corrosion I can find and I've just had the deck up replacing the bilge pump so I'm confident there is none in the hull.

My plan was to mask the gunnels and strip the paint off with a water based paint stripper then sand and repaint. I thought from memory that when I was in the navy we used a light phosporic acid wash on the aluminium upper decks of the DDG's but I can't be sure. (too many beers in my younger days has made the mind hazy) I might give this 'acid' step a miss unless my old navy mates can confirm it.

This clue about prepsol is one of those things that are only discovered by trial and error or through experience from fellas like you.

Thanks for the hint and happy boating guys.

Garry

[ant180]

Prepsol is okay if it is allowed at least 30 mins to evaporate. It is quite a slow evaporating solvent, and though it may look like it is gone, it hides in scratches and pores for a little while.

Make absolutely sure you use an etch primer on aluminium, as most paints will not adhere for long without one.

I try to stick to 2K etch primers, and 2k paints, as I feel that the catalysed products are more hardy than paints which do not have a catalyst.

One little tip, if possible get an etch primer that will allow you to "wet on wet" the first coat of paint on top. This causes the first coat to "burn in" to the etch primer and get a better bond.

Edit:

I will not use anything that comes in a spray can, from what i've seen its all junk. Be careful spraying any paints, especially 2K paints, which contain Isocyanates. No respirators are rated for Isocyanate use, and technically these paints require a full face mask supplied with air from away from the spraying area. You only get one pair of lungs.

Edited January 23, 2009 by ant180