Anodizing a Weldment of Different Aluminum Alloys

A. Trista

Yes it is possible to anodize a part that is consisting of 4 different aluminum alloys, but the results may not be favorable. the 4 alloys you plan to use anodize differently meaning some will anodize more quickly while others will take more time. what this equates to is varying thickness from alloy to alloy and a good chance of color variation. you might be able to get away with hard coating the parts but you could end up with a collage of different colors because each alloy takes on a different color during the hard coat process.
the ranges of color may be more dramatic depending upon the thickness you are wanting to attain.

A. Hello Trista,
In addition to the other excellent advice, will you have the assembly heat treated after welding? This will not improve the colour coordination of the various alloys when finished, or how quickly they build in the tank, but the welding itself creates zones where anodizing is unpredictable as temper is changed, and welding rod is a different animal entirely... It's like you've added an untreated casting into a wrought assembly. So the corrosion resistance across the finished assembly will be wildly variable, and it may be quite a sight even just visually. My shop refuses multi-alloy assemblies flat out, and if something arrives with welds, there is additional communication prior to accepting the job, because of the issues both functional and aesthetic that always arise.