Fixing corroded aluminium ?

[Boo2]

Hi,

Someone who is a) strong and b) knows what they are doing has just removed some stanchion bases from Sunrunner. The bases are recoverable and I would prefer to reuse them rather than drill more holes in the toe rails and deck to suit new ones with different mounting arrangements (exact replacements seem impossible to find).

My question is, can anything be done about the corrosion and salts the old bases have accumulated over the years ? I could obviously go over them with emery but that would take off all the remaining anodising and I don't want to do that as I have no way to re-anodise and they will just corrode faster.

If the material was ferrous then there are various rust restorer products available that will chemically convert the rust back to metal, but is there anything that will do the same job for anodised aluminium ? Or anything that will help at all ?

Many thanks,

Boo2

 

[Sailingsaves]

I am unsure of this, but as no one else has replied, perhaps they will jump in to correct me.

Vinegar (ethanoic acid or acetic acid) has some affect upon aluminium corrosion I believe; whether it terminates the corrosion, or removes it I am not sure. If it does either of these things then great. Then use etching primer paint to protect the cured aluminum? Followed by a top coat of suitable paint?

edit:
Google says this:
"3. Treat any superficial corrosion present, using an inhibitive wipe down material. An alternate treatment is processing with a solution of sodium dichromate and chromium trioxide. Allow these solutions to remain on the corroded area for 5 to 20 minutes, and then remove the excess by rinsing and wiping the surface dry with a clean cloth.

4. Overcoat the polished surfaces with waterproof wax.

Aluminum surfaces that are to be subsequently painted can be exposed to more severe cleaning procedures and can also be given more thorough corrective treatment prior to painting. The following sequence is generally used:

1. Thoroughly clean the affected surfaces of all soil and grease residues prior to processing. Any general aircraft cleaning procedure may be used.

2. If residual paint films remain, strip the area to be treated. Procedures for the use of paint removers, and the precautions to observe, were previously mentioned in this chapter under "Surface Cleaning and Paint Removal."

3. Treat superficially corroded areas with a 10 percent solution of chromic acid and sulfuric acid. Apply the solution by swab or brush. Scrub the corroded area with the brush while it is still damp. While chromic acid is a good inhibitor for aluminum alloys,......."

"Treatment of Anodized Surfaces

As previously stated, anodizing is a common surface treatment of aluminum alloys. When this coating is damaged in service, it can be only partially restored by chemical surface treatment. Therefore, any corrosion correction of anodized surfaces should avoid destruction of the oxide film in the unaffected area. Avoid the use of steel wool, steel wire brushes, or severe abrasive materials.

Aluminum wool, aluminum wire brushes, or fiber bristle brushes are the approved tools for cleaning corroded anodized surfaces. Care must be exercised in any cleaning process to avoid unnecessary breaking of the adjacent protective film. Take every precaution to maintain as much of the protective coating as practicable. Otherwise, treat anodized surfaces in the same manner as other aluminum finishes. Chromic acid and other inhibitive treatments tend to restore the oxide film."

second hit from this search:

https://www.google.co.uk/webhp?sour...spv=2&ie=UTF-8#q=stopping+aluminium+corrosion

 

[Floyd Raser]

I would sugggest you look at the classic car restoration suppliers websites. I have had a quick scan of Frost's site and they do an annodising removal chemical and an annodising kit to put it back! Ok, that may not be practical but it's a good start. From experience I know that Frosts are expensive as most of their stuff is imported from the US.

http://www.frost.co.uk/aluminium-anodising-kit.html

 

[skipmac]

Doesn't look like there is enough anodizing left to worry about. I would take it down to clean metal and treat it with a proper, etching aluminum primer.

 

[Plevier]

Doesn't look like there is enough anodizing left to worry about. I would take it down to clean metal and treat it with a proper, etching aluminum primer.

+1

Also look up Alodyne and Aluchrom. These are the nearest you can get to anodising non-electrolytically (and overlapping with the processes Sailingsaves refers to.)
I think if cosmetically acceptable the etch primer followed by ideally an epoxy paint or at least Primocon would be better.

 

[rogerthebodger]

Find some one who repairs aluminium outboard propellers. this is mostly done by building up any corroded material by welding. To weld aluminium correctly it must ne cleaned properly and the welders have to do this anyway.

Once back to required shape take it to a company who specialising in anodizing to strip and re anodize to reinstate the protective coating.