Topic: Aluminum corrosion help

[Prospect]

I own a sail boat and each year the mast is taken down for winter storage. I noticed corrosion on the mast and was wondering how to repair it. The mast is about 30' long so anodizing is not a possibility. I was thinking of using a wire brush to get some of the corrosion off and using jbweld to fill the pitting. The pitting is about 1mm deep. I'm not concerned about structurally integrity too much as the aluminum thicknessess is about 4.5mm.

I saw videos of using aluminum rods and blow tourch to braze and build up aluminium but I think I might go the JBweld route. I'm hoping to stop the corrosion.

[scottly]

Check out Sharkhide:
https://sharkhidestore.com/

[BenelliSEI]

I think that is corrosion that’s attacking some porosity in the original casting? Canadian Tire used to sell a product specifically for repairing aluminium. It came in a toothpaste tube and squeezed out in a liquid paste consistency. Dried in a few hours. It was easy to sand when dry (easier than JB WELD!). I think it was in a red and white tube and called “Liquid Aluminum”. Try looking in their marine section. I’ll see if I still have a tube somewhere.

[calj737]

Check out Sharkhide:
https://sharkhidestore.com/

An excellent product. Have used it for years on my boat trailer, an aluminum boat, and wheels.

I’d repair/fill the pitting then either develop a regimen for maintaining the protective coating or try cold anodizing coating. When folks weld up anodized tubing for tuna towers and such, the welds get treated with a cold anodizing liquid. It is pretty durable stuff.

A decent source for info-
https://www.practical-sailor.com/sails-rigging-deckgear/revive-your-mast-like-a-pro-2

[Prospect]

Thanks for the info. Very informative. Do you think using aluminum brazing rods and MAP gas is a good method to build up the corroded area?

I think cold anodizing is not possible because of the size of the mast and transportation. I think I might apply a protective coating afterwards.

Check out Sharkhide:
https://sharkhidestore.com/

An excellent product. Have used it for years on my boat trailer, an aluminum boat, and wheels.

I’d repair/fill the pitting then either develop a regimen for maintaining the protective coating or try cold anodizing coating. When folks weld up anodized tubing for tuna towers and such, the welds get treated with a cold anodizing liquid. It is pretty durable stuff.

A decent source for info-
https://www.practical-sailor.com/sails-rigging-deckgear/revive-your-mast-like-a-pro-2

[scottly]

Thanks for the info. Very informative. Do you think using aluminum brazing rods and MAP gas is a good method to build up the corroded area?

I doubt a regular MAP gas torch would put out enough heat to melt the rods properly, with that much mass sucking the heat away. If it's only a cosmetic issue, I would just use JB weld.  

[RAFster122s]

Will the mast fit inside a house rain gutter? Then a liquid coating might be possible.

[BomberMann650]

Thanks for the info. Very informative. Do you think using aluminum brazing rods and MAP gas is a good method to build up the corroded area?

I doubt a regular MAP gas torch would put out enough heat to melt the rods properly, with that much mass sucking the heat away. If it's only a cosmetic issue, I would just use JB weld.

The aluminum solder/braze sticks sold at harbor freight will flow under map gas.

Tried em once.  Then decided a tig welder would be worth the money. 🤷🏻‍♂️

[calj737]

Thanks for the info. Very informative. Do you think using aluminum brazing rods and MAP gas is a good method to build up the corroded area?

I think cold anodizing is not possible because of the size of the mast and transportation. I think I might apply a protective coating afterwards.

I think you’d better determine the actual composition of the mast before you undertake any repair. Is it T-6, is it not? That determines whether you can use any heat technique to repair it.

MAPP will work to melt aluminum brazing rods, even on that thicker material (4.5mm isn’t that thick) but I’d probably opt for an epoxy filler since it’s cosmetic and go with protection afterwards. You might be really well served to perform a top-to-bottom gentle scuffing of the entire mast and protection regimen to follow.

[scottly]

MAPP will work to melt aluminum brazing rods,

Real MAPP gas, which contained acetylene, hasn't been made since 2008. The substitute marketed as MAP is only 100 degrees or so hotter than propane.

[calj737]

MAPP will work to melt aluminum brazing rods,

Real MAPP gas, which contained acetylene, hasn't been made since 2008. The substitute marketed as MAP is only 100 degrees or so hotter than propane.

And it will create a flame over 3700* which is about 5x hotter than needed to melt an aluminum brazing rod. It’s even hot enough to break the oxide layer.

[Kelly E]

Good thing I have a couple of bottles left of the real stuff.

[Prospect]

Thanks for all the replies. I decided to go the JBweld route. Worked great.  Doesn't look very nice since there is a big colour contrast between the aluminum mast and JBweld. But, it's about 25' up the mast so very hard to see.