Aluminium casting corrosion what to do?

[TQA]

I have a pair of Barient 32 st winches which do the business on my 1978 boat. I am assuming they are the originals. View attachment 44314

One of the bases has some corrosion on the upper lip of the base. Now it may well be that when I strip them down I will discover that the bases have severe corrosion which is a known issue and I will have to get new bases from Arco winches in Oz.

However if the corrosion is superficial and in areas which are cosmetic I plan to fill with some epoxy based filler and paint.

My question is what is the best way to prepare the corroded area before using the epoxy and should I use any primer.

My thinking is wire brush and then epoxy but perhaps there is something better I can do.

 

[ReefMagnet]

I just repaired a leaky water jacket on a small outboard that was suffering corrosion. I used a die grinder with a carbide bit to prepare the repair area (a dremel would do the same job) to clean metal then cleaned it all up with acetone afterwards. I used JB Weld epoxy which is almost the same colour as the casting when set. From what I've read on the Internet (which must be true!) JB Weld sticks like poop to a blanket when used as a filler on aluminium castings. I left my repair unpainted, and I had to file some of the epoxy to reform the machined surface that a gasket sealed against and I was very impressed with it (no leaks - yay!). Having said that, I did repair a corroded mast base once using regular thickened epoxy with decent results, too. In that case I did paint the base afterwards and I used etch primer, undercoat and then topcoat to do the job.

 

[vyv_cox]

Conventional advice is that you need an etch primer on aluminium before painting. I have had great success with Hammerite special metals primer, used it for a radar scanner adaptor plate that I made well over ten years ago and still in good condition. I suspect that epoxy filler might be best on the untreated aluminium after vigorous abrading but then give the whole lot a few coats of paint after priming.

 

[TQA]

So abrade back clean with acetone or maybe toluene then JB Weld.

OK just got to keep my fingers crossed that the damage is cosmetic.

 

[superheat6k]

I had a casting fizzure in the Vetus helm ump on my last boat. I fixed it with aluminium brazing rods.

Try here ...

http://www.aluminiumrepair.co.uk

 

[ReefMagnet]

I had a casting fizzure in the Vetus helm ump on my last boat. I fixed it with aluminium brazing rods.

Try here ...

http://www.aluminiumrepair.co.uk

That's not a bad idea. The castings are most likely a silicon alloy so you'd need to take it to an expert welder unless you were reasonable at it yourself. Then if you did that you may as well get them to TIG it and any decent tradesman would also be able to grind it all back into reasonable shape when done.