Spots on aluminum after PAA

[KirbyWan]

Howdy all,

I'm Phosphoric Acid Anodizing full sheets of 2024-T3 Bare aluminum and some sheets come out with spots on them. I have included a couple of pictures. The spots are about 1/4 inch across. I'm a bit stumped as to the cause. I took a 3M abrasive pad and rubbed a few of the spots and reran the sheet but they were still visible, but I didn't want to get too aggressive with them. We are following a process similar to BAC5555, with a solvent wipe, aqueous degreasing, sulfuric acid/sodium dichromate etch, PAA and rinses with water break free check between each. Any suggestions?

http://files.engineering.com/getfil...4-87e0-f13b435b50dd&file=20140714_094931a.jpg

http://files.engineering.com/getfil...c-938d-4514416d832f&file=20140714_094953a.jpg

Thanks,

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.

 

[WKTaylor]

In-house or vendor processing?

Suggest submitting process info, photos and questions to...

http://www.anodizing.org

http://www.metalfinishing.com

http://www.finishing.com

May be something as simple as surface prep or bath agitation.

Regards, Wil Taylor

Trust - But Verify!

We believe to be true what we prefer to be true.

For those who believe, no proof is required; for those who cannot believe, no proof is possible.

Unfortunately, in science what You 'believe' is irrelevant – "Orion"

 

[KirbyWan]

I'm leaning toward bath agitation on the Aqueous degreaser (Cee Bee 300LF). We shut it off to put the sheet in the tank, otherwise a full sheet of 4'X8' thin aluminum gets knocked about due to the circulation. I thought we should leave it off, which may be the source of our problem, but we ran a sheet where we turned the circulation back on after the sheet was settled in the tank and it seemed to work better.

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.