Aluminium Masts Oxidizing

[swami maximus]

I was wondering what I should do with my mast oxidation. The mast boot didn't have a plug of sorts along the sailtrack, and as such all the rain and spray just gathered there in a pool in the boot. The oxidation is spread under the paint and is about the area of the palm of a hand. Is there a product that I can use to clean this up and prevent spreading? I am going to dry the boot out and plug the track to allow water to escape rather than collect.

In advance, thanks.

Maximus

[Alan Wheeler]

Getting rid of the oxidation is a difficult one. The best method is to use a steel brush on a grinder and simply grind it away so as you have good clean alloy left. Then you need to Acid etch it and then paint it with an etch primer and undercoat and top coat.
I imagine the mast step is SST. The ally will corrode when it is in contact with the SST via water between the two.

[Benjamaphone]

For any contact point between stainless and aluminum you should add some type of isolator to avoid any corrosion. There is a product called Tef-Gel that I have used a lot that works great for contact with any nuts, bolts or other stainless hardware onto aluminum. It’s from Teflon and is designed for this particular application (Alum + other metals). I agree with Alan that you should grind down the oxidation that has already taken place and refinish as he suggested. After you're done cleaning everything up, apply an anti-corrosion product like Tef-Gel to prevent it from happening in the future.

Originally Posted by Alan Wheeler

I imagine the mast step is SST. The ally will corrode when it is in contact with the SST via water between the two.

Not quite true...

For a galvanic cell to be established there has to be a "round-trip" circuit created between the two metals, AND through the water. Merely a water bridge between two metals that are otherwise electrically isolated does not cause corrosion.

Put a piece of SS and a piece of aluminum in a dish with some salt water and nothing interesting happens, unless and until you electrically connect the two pieces of metal either by direct contact or with wire or other conductive bridge so the electrons can have a path back. Viola' a battery and dissovling aluminum!

[Alan Wheeler]

when it is in contact

Ummm didn't you read the Contact bit?? :-)
You can have SST deck steps that the Aluminium (or how ever you US guy's spell it)mast sits on. It will be in direct contact. And it will corrode and the only two ways to stop it is to isolate it with a coating or pad to sit on or to ensure water never gets in there at all with a collar or sealant.
I am sure Tefgel works, but I like to use Lanocote. It is great stuff for that kind of use.

[Celestialsailor]

I believe he is talking about where the mast passes through the coach roof. There is a rubber 'boot' that prevent water from coming inside the boat. I did not see any mention of a SST mast step or base. I am imagining that the boot, from its shape pools water somehow causing the corrosion. If so...There is a mast tape avaiable that replaces the boot altogether. How ever you will have to wire brush away the corrosion, prime and paint first.

Originally Posted by Alan Wheeler

Ummm didn't you read the Contact bit?? :-)
You can have SST deck steps that the Aluminium (or how ever you US guy's spell it)mast sits on. It will be in direct contact. And it will corrode and the only two ways to stop it is to isolate it with a coating or pad to sit on or to ensure water never gets in there at all with a collar or sealant.
I am sure Tefgel works, but I like to use Lanocote. It is great stuff for that kind of use.

Sorry if I misunderstood, it was the "contact via the water" and I thought you menat they did not need to be in direct contact.

Lanocote does work just as well as tefgel, but it does tend to get a bit runny when it's hot. I suspect tefgel is a bit more permenent, but have no real data to support that assumption.

[Benjamaphone]

Originally Posted by GreatKetch

I suspect tefgel is a bit more permenent, but have no real data to support that assumption.

That's right. Tef-Gel is almost the consistency of a grease. It doesn't get runny and won't wash away over time. It's a little expensive to be used as liberally as a grease though and comes in a small syringe type of tube. It's great for applying to the inside of a nut to protect the threads, or to an area that is exposed to contact with dissimilar metals, salt, etc.

[Joli]

We use Lanocote. One jar has lasted a looong time. I try to disasemble the rig every 2~3 years and dip the fittings and re-assemble. Never tried Tef-Gel but heard it is good also.

[GordMay]

Tef-Gel is 40% Polytetrafluroethylene (PTFE, or “Teflon”)
Tef-Gel protection against corrosion - Material Safety Data Sheet

LanoCote is <60% Lanolin + 10% Fish Oil.
http://www.crc.co.nz/msds/3220.pdf