Surface Conditioning Prior to Clear Anodize

[cls3277]

thread116-226362

In the original thread referenced above, it was suggested that there were a few alternatives for surface finishing to remove machining and handling marks: I was hoping someone could help me with the following:

If you use a vibratory tumbling with plastic media, I would have thought the pieces would create new marks as the pieces hit each other in the tumbler? Do you just severely limit the pieces you put in the tumbler, or do you not find this to be a problem?

If you were going to do it via sanding on a lathe, would you recommend say a 160 grit and then jumping to a 320 grit, or would that still be too coarse and show up in the final part?

Has anyone had a problem with pitting showing up after the etch and clear anodize, or are these likely handling marks being confused as pitting?

If you are trying to achieve a mirror finish and you buff the pieces with a cotton or sisal wheel and polishing compound, does the subsequent frosted finish still have a mirror like appearance? In this case, would you skip the etch?

To avoid having to surface finish to remove machining marks, has anyone used a double etch successfully? I can't imagine the etch taking enough material off to remove these. Are there any chemical alternatives?

Thank You in Advance for Any Opinions!

 

[cls3277]

We are using Mil Spec 8625, Type II, Class I decorative with 201 called out (15 minute anodize time). We have tried a deep etch, but are now trying either a 1 minute etch or just a soap and deox process, but it doesn't seem to make a difference. In an ideal world, we'd prefer to use a chemical pre-treatment to remove the pitting or machining marks. We have tried 6063-T6 alloy and 6061-T52 alloy 1'' aluminum rounds as the base material, and have had marginally better results with the 6063, but are having a whole host of problems. In general, we have been machining a .010 dia skin cut from the diameter of the piece to clean up the outside.

The aesthestic problems we are having include (i) pitting or machining marks showing trough on the final product, (ii) a tan discoloration, (iii) die marks running the entire length of the piece that were not visible prior to anodizing, (iv) water marks or white discoloration blotches on the pieces which are sometimes in limited spots and sometimes effect an entire rack.

 

[cls3277]

This is a link to photos of the common errors we are encountering as well as a PDF file showing some of the processes we have tried beside a clear anodized control piece we are trying to match. [URL unfurl="true"]https://drive.google.com/a/monarchmetal.com/folderview?id=0B_-g1ae_44AtbmJUODVWazd4bzg&usp=sharing[/url]