2024-T81 bare has contamination after FPL etch. Any ideas why?
2024-T81 bare has contamination after FPL etch. Any ideas why?
(OP)
Howdy all,
So we have a PAA line and we had one piece of metal that had a brown color when it came out of the FPL tank. Here's the process:
Solvent wipe
15-30 minutes in Cee-Bee 300LF
5 minute rinse in tap water
10 minutes in Sulfuric acid/sodium dichromate etch
5 minute rinse in tap water
We would normally go on the Phosphoric acid anodize step, but our process operator stopped because it had a streaks. She re-ran it and it got even worse. Check out the pictures below.
The material is 2024-T3 bare per QQ-A-250/4 which had been aged to the -T81 condition before processing.
This was run at the same time as other details made of 2024, though different sheets, which did not have a problem, see the sheet just above in the first picture. I can't figure out why one piece of 2024 would come out so different from parts run at the same time.
Has anyone seen this issue before or recommend a plan for determining the root cause?
Thanks for your help.
-Kirby
Pictures:
http://files.engineering.com/getfile.aspx?folder=7...[1].jpg
http://files.engineering.com/getfile.aspx?folder=8...[1].jpg
So we have a PAA line and we had one piece of metal that had a brown color when it came out of the FPL tank. Here's the process:
Solvent wipe
15-30 minutes in Cee-Bee 300LF
5 minute rinse in tap water
10 minutes in Sulfuric acid/sodium dichromate etch
5 minute rinse in tap water
We would normally go on the Phosphoric acid anodize step, but our process operator stopped because it had a streaks. She re-ran it and it got even worse. Check out the pictures below.
The material is 2024-T3 bare per QQ-A-250/4 which had been aged to the -T81 condition before processing.
This was run at the same time as other details made of 2024, though different sheets, which did not have a problem, see the sheet just above in the first picture. I can't figure out why one piece of 2024 would come out so different from parts run at the same time.
Has anyone seen this issue before or recommend a plan for determining the root cause?
Thanks for your help.
-Kirby
Pictures:
http://files.engineering.com/getfile.aspx?folder=7...[1].jpg
http://files.engineering.com/getfile.aspx?folder=8...[1].jpg
Kirby Wilkerson
Remember, first define the problem, then solve it.





RE: 2024-T81 bare has contamination after FPL etch. Any ideas why?
One of my machinist friends found a complete micrometer caliper in an aluminum bar; it ruined an expensive cutter.
Mike Halloran
Pembroke Pines, FL, USA
RE: 2024-T81 bare has contamination after FPL etch. Any ideas why?
RE: 2024-T81 bare has contamination after FPL etch. Any ideas why?
My marine exhaust shop, where 316L is the 'cheap stuff', had a sheet of '304' lying around that they used for some incidental brackets welded to some very expensive and very complicated custom tubework made of 25-6SMO or AL6XN or something similar.
The brackets disappeared completely in the pickling bath.
The sheet was mild steel that someone had acquired for a home project.
Mike Halloran
Pembroke Pines, FL, USA
RE: 2024-T81 bare has contamination after FPL etch. Any ideas why?
thanks for the stories of suspect material.
-Kirby
Kirby Wilkerson
Remember, first define the problem, then solve it.
RE: 2024-T81 bare has contamination after FPL etch. Any ideas why?
For example, some results on FPL http://www.finishing.com/191/21.shtml
RE: 2024-T81 bare has contamination after FPL etch. Any ideas why?
Mike Halloran
Pembroke Pines, FL, USA