Is anodising aluminium necessary

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flylhp

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Hi All

Can any one help I wish to strengthen a external locker cover by fitting a strip of aluminium along the edge 3/8 x 1 1/14 x 44 ins is it essential to get it anodised or can I get away without.


flylhp
 
If it is pure ally it is no good whatever you do. I expect it is duralumin which won't really need anodising - paint or varnish but keep an eye on it and don't let any brass get near it.
 
Try your local airfield engineering sheetmetal bashers. Get a piece of pre anodised extrusion or sheet. Will cost, but is the right stuff. You will still need to treat the cut ends though.
 
Anodising your aluminium alloy will do three things (a) harden the surface - aluminium oxide is extrememly hard so it will be scratch resistant, (b) resist corrosion, (c) colour the piece. So if you want your strap to look professional and clean and tidy over a long period then you should get it anodised. You also have to pick the right process; usually a 'hard anodise' in a sea environment.
HOWEVER, getting the job job done is not so simple and can be expensive. If you are determined then talk to a company such as Poeton, who have a number of sites around the country but they may want detail you dont have, such as the alloy grade. You have some alternatives. There is a treatment which is a simple brush-on chromate protection called Alocrom 1000 (may not be the right spelling here) but getting some is not easy (if you find someone willing to sell a small quantity let me know please); and you can do what I did last time which is spray the aluminium with a laquer. This lasts for maybe a couple of years before it needs replacing (maybe less if the piece is subject to wear) and eventually the finish becomes pretty poor. It provides no hard protection and no colour but will stop the more obvious corrosion.
I haven't mentioned painting, mainly because this is something I never did professionally, and I think if you wanted to you could paint with something like an epoxy two part, but I don't know if it needs a pre-treatment.

Good luck
 
Alochrom is the correct spelling. Can't help with suppliers though. It was/is used in the aerospace industry. Whole range of colours available. A Google will find it.
 
You can paint but you do need a primer. I have used it on booms and masts- even then.

I am in the process of fitting a second hand Radar scanner.

The scanner was fine, but the bracket. Manufacturers paint pealing off and white powder under.

I started to remove the paint, then, long before I was finished, I phoned a local anodising company.

Sorry sir, but we will have to charge you the £25 minimum charge and don't bother removing the paint we'll do that.

I collect it next week. Must be better than painting.

I'm quite happy at that.

Iain
 
This has got me thinking.

When I've done odd jobs on my boat using aluminium from a builders merchant I've always assumed that it was anodized. Was I right?
 
If you wish to do it properly then I suggest that you get some marine grade aluminium. The easiest way to get a small quantity is to visit an aluminium boat builder - tell him what you want it for and he should crop you off some of either structural or non structural grade (there are also a number of grades according to whether he cuts it from plate or an extrusion, but he will know which you need).

It will not need protection of any kind whatsoever unless you want to do so for cosmetic reasons. However, if you are fixing it onto painted timber or fibreglass (or indeed anything else), I suggest that you bed it with a sealant (eg Sikaflex 291) to stop moisture collecting underneath - otherwise the stagnant damp conditions can lead to corrosion there regardless of whether it is painted/anodised or not.

If you do not use a marine grade alloy, the next best solution (and probably more expensive) would be to have it anodised, but whatever you will likely have problems with it downstream.

John
 
Just a thought - is it necessary to use a metal strip?
an epoxy glued wooden strip could be adequate especially with glass fibre over the top. This would not need screws. Alternatively use epoxy/glass to fix and cover the aluminium then again water cant get at it, so again no screws and no worries about the anodizing.
And if you still prefer a bolted on metal strip that metal strip you specify sounds very like a small genoa track extrusion ..
 
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