Anodising Aluminium

[mick maxen]

Has anyone on here have any experience with anodising. What I would like to know is how to prepare the surface before anodising. As aluminium is soft and easily marked, I have thought of gently shot blasting the surface with glass beads to hide any scratches. This would also give the surface a more interesting look than just flat and shiney.
Does anodising take evenly to a uneven surface or does it have to be polished for the best effect.

Mick.

[Swamptroll]

Prepare it the way you want it to look when finished. There are several other factors like depth of penetration and colour to think about also, it can be polished or left unpolished. Anodize process forms a layer of aluminum oxide.on the surface to the depth of penetration requested, but it is only a few thousands deep.

[BIGGUNDOCTOR]

The final finish is dependent on the finish at the start, as mentioned before.

My Dad built the anodizing tanks at one of the Air Force bases he was stationed at for doing the propeller blades on the C-130's. They were doing a hard anodize for durability. Anodizing is nonconductive, and they checked for coverage by using a multimeter. The anodizing process is pretty dependent on a good, and very controllable power source.

[LDW]

Its been about 13 years since I worked in a plating shop, but I used to be a maintenance supervisor at a pretty large plating and anodizing shop. Pre-treatment for anodizing alluminum was an etch in a caustic solution. This resulted in a black smut so after the etch there was a de-smut made up with nitric acid. The alluminum would look clean after coming out of this. Then straight to the anodize tank. BIGGUNDOCTOR is correct about the conductivity so when you would anodize the current would be highest when the metal was put in, you could actually watch the amperage decline as the layer of anodize increases.