Oven cleaner to clean mast? Why not?

[zachduckworth]

Hi all,

I’ve decided to remove the anodizing from the mast on my 1984 Islander Bahama 30. There is a lot of corrosion around the fittings. I’m going to pull the mast this summer, and it down to bare metal, bed the fitting with Tefgel, and then put her back up. I don’t mind the bare aluminum look, and painting is too expensive at the moment (trying to buy a house…).

I’ve seen videos on how to sand down aluminum but that seems like the hard way to do it. From what I’ve read, the anodizing is harder than the aluminum so the result is uneven and the sander breaks through the anodizing and eats into the aluminum.

Car guys recommend the much faster and apparently more consistent method of spraying oven cleaner onto it and letting it sit. Lye, or anything with caustic soda is also suggested.

I want to do this project myself to save money. The caustic soda route seems like it would work too. Any reason it wouldn’t? Any thoughts appreciated!

[GordMay]

Sodium hydroxide [caustic soda or lye] is a strong alkaline compound, and is the active ingredient, in most drain and oven cleaning products.
Pre-anodising etching, in sodium hydroxide, prepares the aluminum for anodizing, by chemically removing a thin layer of aluminum. This alkaline bath gives the aluminum surface a matte appearance.
Sodium hydroxide might react, with the base aluminum, more readily, and at a higher rate, than with the aluminum oxide*.
I'd test it first, in a small, non-critical area, before proceeding.


* Aluminum anodizing is an electrolytic process, used to increase the thickness, of the tightly adhering oxide layer, that forms naturally, on any aluminum surface, exposed to air.

[s/v Jedi]

You must leave the anodizing intact as much as possible. Remove the fittings, then the corrosion, then mount the hardware using isolation materials (UHMW tape etc.) and Tefgel. You can spray a corrosion inhibitor at/around the fittings and where galvanize was removed.

Bare aluminum is much worse than anodized aluminum. Paint is somewhere in the middle.

[GordMay]

Originally Posted by s/v Jedi

You must leave the anodizing intact as much as possible ...
... You can spray a corrosion inhibitor at/around the fittings and where galvanize was removed...

Galvanizing and anodizing are two distinct & separate processes, used to treat metal.
The anodizing process involves increasing the thickness of the alumanum's natural [protective] oxide layer.
In contrast, the galvanizing process deposits a layer of zinc, to protect metals from rusting.


PS: I had to edit my post #2, because I [first] miss-used 'galvanized', where I intended 'anodized'.

[SailingHarmonie]

Why not? Because it will dissolve your mast that’s why! You do not have the control over concentration temperature, reaction time, or application to make this reaction useful.

It dangerous is several ways and just a bad idea. Do not do it.

If you don’t believe take a cheap aluminum pan and spray it down with oven cleaner. Watch what happens. Be sure to do this outside, it evolves highly flammable hydrogen gas.

[zachduckworth]

http://https://youtu.be/bNAB45zQUtk?feature=shared

Here is an example of the process. This guy appears to know how to work with aluminum since he owns the business. Of course there’s a question of what exact grade pieces he’s using. But the trick clearly works, and the parts do not appear to be eaten by the bath. My though would be to do this outside, catch the material, then dilute and dispose of it.

[Cheechako]

Originally Posted by s/v Jedi

You must leave the anodizing intact as much as possible. Remove the fittings, then the corrosion, then mount the hardware using isolation materials (UHMW tape etc.) and Tefgel. You can spray a corrosion inhibitor at/around the fittings and where galvanize was removed.

Bare aluminum is much worse than anodized aluminum. Paint is somewhere in the middle.

^ THIS! Why remove what anodizing you have left?
They all corrode, especially if painted in my experience. Clean up and rebed your fittings better isolated if they are not aluminum.

[SailingHarmonie]

Originally Posted by zachduckworth

http://https://youtu.be/bNAB45zQUtk?feature=shared

Here is an example of the process. This guy appears to know how to work with aluminum since he owns the business. Of course there’s a question of what exact grade pieces he’s using. But the trick clearly works, and the parts do not appear to be eaten by the bath. My though would be to do this outside, catch the material, then dilute and dispose of it.

Handling sodium hydroxide with no gloves, and especially no eye protection is not indicative of somebody who “knows what they are doing”.

There are grades of aluminum alloy that can live long and happy lives with no anodizing in a marine environment. They are rarely seen in masts annymore and since the manufacturer went to the expense of anodizing your mast you can be pretty sure your mast in not of such a grade of Al. Leave the existing anodizing in place. It is not the cause of your problems.

But as always it’s your boat, but if you do use sodium hydroxide, please, please use goggles. That stuff will turn your corneas opaque very, very fast.

[Iron E]

Originally Posted by zachduckworth

http://https://youtu.be/bNAB45zQUtk?feature=shared

Here is an example of the process. This guy appears to know how to work with aluminum since he owns the business. Of course there’s a question of what exact grade pieces he’s using. But the trick clearly works, and the parts do not appear to be eaten by the bath. My though would be to do this outside, catch the material, then dilute and dispose of it.

So, you plan on having a container large enough to hold your mast, fill it with oven cleaner, and then submerge your mast until anodizing is removed.

On a side note, I'll bet that car parts are anodized strictly for aesthetics, whereas a mast would have a thicker and more durable anodization to protect against harsh marine elements.

[SailFastTri]

It seems OP is looking for affirmation, not advice. Doesn’t have the budget to fix it right, so he’d rather make a mess of it. I wonder how much he’ll get for that boat when the mast is a POS. Total cost of ownership = purchase price + maintenance & ops + upgrades - sell price.

[Franziska]

Zach,

suggestion, get a piece of scrap mast or boom extension, make a try and report back with the results.

It's not a great idea, but if you feel it is right, make a trial first on a piece of scrap before messing up your mast.

Another way would be to clean up all corrosion locally, treat as suggested above by many others and then film wrap the mast before mounting the hardware new. The film helps further in separating dissimilar metals when mounting the fittings back. Still, by all means use lots of Tefgel and plastic washers where needed.

[Don C L]

Originally Posted by s/v Jedi

You must leave the anodizing intact as much as possible. Remove the fittings, then the corrosion, then mount the hardware using isolation materials (UHMW tape etc.) and Tefgel. You can spray a corrosion inhibitor at/around the fittings and where galvanize was removed.

Bare aluminum is much worse than anodized aluminum. Paint is somewhere in the middle.

Yeah I'd agree with this, don't attack the anodizing, though I think bare aluminum is fine if it is the right kind. My mast has been bare for 60 years.