Changing colour on anodizied fronplates

[Jan Dupont]

Can e.g a silver anodizied front plate be anodizised in another colour without any other preparation but degreasing or does it have to be sanded first ?

[Steve Dunlap]

The old finish will need to be completely removed first. Sanding will work, but so will several chemicals.

[Jan Dupont]

Thanks Steve.
Do you know which chemicals ?

[Steve Dunlap]

The easiest to obtain is sodium hydroxide, or lye. Mix 4 to 6 oz to a gallon of water. Read the warning labels. The solution will get very hot, so do not mix in a glass container, it may break. Plastic is best. You will need good ventilation and NO open flames. Do not leave the piece in the solution too long or it will begin to dissolve and leave the surface rough.

If you plan to have the piece anodized by a commercial facility, let them remove the old surface.

[Jan Dupont]

Thanks a lot for your help, Steve

[Stuey]

Sorry to piggyback onto your thread, Jan, but may I ask Steve an on topic question? I've only just been thinking about this myself.

Steve, if you wish to remove the black anodising of a faceplate with NaOH because you wish to have a silver anodised surface (ie. reverse of Jan), does it need to be re-anodised? Or is there a way to remove the dye and leave it anodised silver; say, if you are very careful about the time limit you leave it in the solution?

Thanks

Stuey

[Jan Dupont]

Stuey
Your'e welcome. I'm interested to

[Magura]

Originally posted by Stuey
Sorry to piggyback onto your thread, Jan, but may I ask Steve an on topic question? I've only just been thinking about this myself.

Steve, if you wish to remove the black anodising of a faceplate with NaOH because you wish to have a silver anodised surface (ie. reverse of Jan), does it need to be re-anodised? Or is there a way to remove the dye and leave it anodised silver; say, if you are very careful about the time limit you leave it in the solution?

Thanks

Stuey

It needs to be anodized again. The dye is in the oxide layer.


Magura

[Stuey]

Thanks Jan!

Magura, I thought as much. I was hoping the dye could be removed without removing the oxide layer. I had some idea it permeated pores in the oxide or something like that and may fade before the oxide is touched.

Oh well!

Cheers

Stuey

[Steve Dunlap]

Magura is correct. The dye soaks into the very tiny pores in the oxide layer. The layer is then sealed by immersing in boiling water, making the dye permanent.