Re-anodising aluminium

[boatsRus]

The silver anodised frames on my 'windscreen' are showing signs of age, with significant amounts of white powder (hydrous aluminium oxide?) building up around some of the corner joins. Can the frames be removed and re-anodised? If so, any recommendations for companies who could do the re-anodising? Or is there an easier solution which can be used whilst the frames are still in situ in order to slow down or stop the oxidisation process? Any advise gratefully received.

 

[whiteoaks7]

Investigate Alochrom (check spelling), a paint-on clear or coloured anodising replacement. I guess removing, stripping, de-glazing, re-anodising and replacing would cost more than new frames!!!

 

[VicS]

There is a firm in Emsworth, RBM Anodising, in Seagull Lane who will probably be able to reanodize them. I know no more about them than their existence though.

You may be able to find others in your Yellowpages.

However other people have found that reanodizing old aluminium items gives rather disappointing results.
The alternative is grit blasting with a soft grit to remove all the oxide, priming with a suitable etch primer and then painting with a chlorinated rubber paint. I got a couple of portholes done like some years ago in the paint testing lab where I worked. Good results but they were done under laboratory condition.

 

[VicS]

[ QUOTE ]
Investigate Alochrom (check spelling),

[/ QUOTE ] I'd forgotten that. Still not sure if it is Alochrom or Alocrom but there are two products, 1000 and 1200 that can be applied by brush, and which are slightly different colours. Is or at least was used in the Aerospace industry. I knew a design engineer from B. Aerospace years ago who used it on an unanodised mast.

 

[Graham_Wright]

[ QUOTE ]
[ QUOTE ]
Investigate Alochrom (check spelling),

[/ QUOTE ] I'd forgotten that. Still not sure if it is Alochrom or Alocrom but there are two products, 1000 and 1200 that can be applied by brush, and which are slightly different colours. Is or at least was used in the Aerospace industry. I knew a design engineer from B. Aerospace years ago who used it on an unanodised mast.

[/ QUOTE ]

It is not the same as anodising. I have components alochromed and the numbers refer only to the colour. My platers assure me that it is a poor relation of anodising but it is not expensive.

 

[fishermantwo]

If you are going to pull the frames apart why not get them powder coated.

 

[VicS]

[ QUOTE ]
why not get them powder coated.

[/ QUOTE ] That would be the best solution of all but I guess it would also be the most expensive! There might be a problem fitting the bits back together due to the thickness of the coating but that depends on the design.

 

[misterg]

[ QUOTE ]
The silver anodised frames on my 'windscreen' are showing signs of age, with significant amounts of white powder (hydrous aluminium oxide?) building up around some of the corner joins.

[/ QUOTE ]

The trouble is that some of the aluminium has been 'used up' in this corrosion, so when you clean it off, you will be left with pitting. While it is entirely possible to re-anodise the pitted metal, it still looks like pitted metal (and the stripping and preparation for anodising will probably expose more damage). Unless you have sufficient material to be able to machine off the damage (unlikely), I think you either have to accept a pitted appearance, or fill & paint.

I've found that you can improve the appearance of corroded aluminium by glass bead blasting - this makes the whole surface (pits and all) grey. You could coat this with laquer, but I'm not sure how long it would last on a boat.

It might be worth investigating the powder coating route - it may not be as expensive as people think - we had some small steel casings powder coated a few years ago, and it was surprisingly cheap - they just quoted a per m^2 charge. The coating is as hard as nails, and very firmly attached.

Andy