should I paint my alloy roller reefing boom to prevent corrosion

[lancsjohn]

last autum I purchased a Fantasie 19 yacht and found the 9foot long boom had some white powdery corrosion so I wiped it down with an oily rag which removed the surface deposite and revealed some slight pitting. The mast and boom have been stored under cover all winter and I am now fitting out and wondered if I should paint the boom or treat it in any way?

 

[Dipper]

I treated my first boat's mast and boom which also had some small corrosion spots and mild pitting. In my innocence, I rubbed it all smooth with 1200 grit wet and dry. I am not sure now if this was a good idea as I could have removed some of the anodising (if any) so don't necessarily follow this part of my advice!

Then I applied Owertrol using a soaked rag (very messy - wear gloves or you could just use a brush) and before it was dry (a couple of minutes) I rubbed the surplus off again with a dry cloth. This left a nice protective sheen. I repeated this every few years and it seemed to work - no more corrosion.

My current aluminium mast is painted (not sure why). I have recently repainted it using smooth Hammerite. You need to use Hammerite primer for aluminium first as you can't apply Hammerite directly to aluminium. This seems to have been very successful.

 

[tcm]

I understand that oxides form on raw aluminium in seconds. Painting reduces the speed at which this develops, but essentially if you have painted raw aluminium outdoors, you are simply marking time until it lifts the paint which begins to bubble in two years and lifts flakes of paint off in four.

There are plenty of inland anodising companies who should be able to help.

 

[Dipper]

Without disputing what you say regarding the quick formation of aluminium oxides, presumably if you follow the preparation and application guidelines for the primer (and paint) then this should provide better protection than 2 - 4 years otherwise the manufacturers of the paint would come in for a lot of criticism?

Of course anodising the boom would result in the best long term solution but this is the PBO site – we want to do it ourselves! /forums/images/graemlins/grin.gif

 

[srp]

If you paint aluminium then you must use an etch primer. They used to be zinc-chromate based, but you can't get this now (unless maybe you have access to a friendly aircraft manufacturer). International do a 2 pack etch primer. If properly prepared, primed and then finished with a decent 2-pack paint theres no reason for it not to last - certainly much longer than 2-4 years. Whats the oldest Land Rover or Boeing you've seen????

 

[andy_wilson]

Painting sounds good. You need the physically remove the oxide (wire brush) and apply the correct primer first. you may then want to use some filler if there is severe pitting. Smoth with wet 'n' dry, re-prime if needed. Then apply the correct top coat.

 

[Modulation]

Are there? I have tried several times to get them to do me one off jobs and they dont bother to reply. Do you know of one that might?

 

[Martkimwat]

Is it necessary to remove the old anodizing before using etch primer and then painting or can the etch primer be applied over the existing anodizing, also although removing all fittings would be ideal, is it really necessary?