Chroming aluminium in marine enviroment

[rona]

Help!!

I am designing this IP44 lamp for a yacht using diachroic MR8 lamp that reaches 190° (inside). I used 316 SS but it became black because of the heat.

I think on using Aluminium and chroming it.
Does anyone knows if in a marine enviroment the chroming wont corrode?

any suggestions for Chroming Copper in such enviromental conditions?

[Corpus Skipper]

The aluminum under the chrome will corrode, causing the chrome to flake off. Try anodized aluminum, as in hard tops, towers, rocket launchers......Very shiny and durable. As far as chrome over copper, copper is already used in the chroming process so I guess it would work, but copper corrodes in salt and turns green, which will come through the chrome and stain everything around it green. Or you could just use polished aluminum with a clear coat on the outside. When that flakes off, repolish and recoat. Good luck.

[rona]

Hi Corpus Skipper,
Many thanks for your quick reply.
What do you mean by 'clear coat'? if I'm polishing the aluminium, will it still need the anodising?

[BillyDoc]

Hi Rona,

I would polish to the surface you want, CAREFULLY clean off any polishing compound, and then do a "hard" anodize. You could also do a decorative stain at this point.

Anodizing is very easy to do, I suggest you google on this subject to find out how, and the difference between a hard and “soft” anodize is merely the temperature that the anodizing is done at. If you anodize at near the freezing temperature of the acid solution used (battery acid) the result is very hard and scratch resistant. Also, if you want shiny surfaces the anodize will preserve them. The color often associated with anodizing is actually a dye that is used as a final step in the process, and is purely optional.

You might also want to pay attention to the particular alloy of aluminum used, a marine grade like 5086 would be good, or you could use 6061. Of course the initial forming process you use might preclude either of these.

Bill

[Corpus Skipper]

What do you mean by 'clear coat'?

Just a clear (usually polyurethane) paint.

[rona]

Many thanks to you

[D'ARTOIS]

You may use electrolical polished titanium, available in this sheet, that will neither transfer heat nor will it corrode. The material is available, but not through regular sources. It is only of interest if this is for use in a production process - otherwise the efforts to procure the material is waisted. This is the most expensive and durable solution.

Another solution is to be found in the surfacetreatment of a heatresistant-metal; the surfacetreatment can be of a coating of Indium:
I have the chemical composition of the Indium-solution.

This lamp must cost a bundle!