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topic 26113

White streaks in anodizing due to uneven blasting?


(2003)

Q. To Whom it May Concern:

I am anodizing per Mil-A-8625 [link is to free spec at Defense Logistics Agency, dla.mil] Type II, Class II black on 6061 aluminum which prior to anodizing is being powder glass bead blasted at the customers facility. After anodize the part becomes patchy with white streaks where it appears the blasting is uneven. I have tried varying my Alkaline Etch time from 15 seconds to 2 min. with no improvement. If you would have any solutions on this matter it would be appreciated as it involves large quantity orders and several different jobs.

Respectfully,
Tim

Timothy Furrer
Anodize Shop Manager - Chino Valley, Arizona, USA


(2003)

A. This is VERY simple, follow this instructions :

1) etch in your caustic for 10 sec,
2) 20 sec deoxidize,
3) approx. 45-60 sec in ABF solution.
4) flash anodize for 10 min.
5) GO BACK TO YOUR CAUSTIC ETCH, STRIPPING THE ANODIZE
6) deoxidize the same as before 20 sec.
7) go back to your ABF solution same time
8) anodize for normal time w/your dye and seal

And that's how you get rid of the streaks from any blasting

Sergio G.
- Oxnard, California


(2003)

A. Poor Bead Blasting is poor bead blasting. Excessive pressure and uneven blasting produces uneven appearing parts. The solution is to decrease pressure, use the proper media and blast with even movement. Aluminum will "burn" otherwise. Few people know how much art is involved in cosmetic beadblast. To correct the problem a strip, light & even beadbast, and anodize.

Good Luck.

Bill Grayson
- Santa Cruz, California



To minimize your searching efforts and to offer multiple viewpoints, we've combined some threads into the dialog you're viewing. Please forgive any resultant repetition or failures of chronological order.



Anodizing doesn't remove water stain marks

(2005)

Q. We have received Aluminium Section for Anodising which is having water stain marks on it and we are unable to remove the with caustic etching can anyone suggest any other process for removing this water stains. Alloy is 6061.

Satish Shah
chemicals - Anand, Gujarat


(2005)

A. If the parts can handle the dimensional change, you can etch it, then anodize it, then remove the original anodize in the etch, then anodize it again.

That would probably work, a lot of parts look a lot better the second time around - most of the impurities/stains are incorporated into the original oxide layer and removed when you remove it.

Don't try this with castings though, I imagine it would result in a very poor second anodize due to the other casting constituents.

Good luck.

Jim Gorsich
Accurate Anodizing Inc.
supporting advertiser
Compton, California, USA
accurate anodizing banner


(2005)

A. It has been my experience you need to deox or desmut the part first. If you anodize over a water stain it will set the pattern, and then only mechanical means can remove it.Sometimes it has helped us if we also flash anodize the part .To do this we desmut , rinse, anodize for five min., rinse aind then go back through your regular process.

Mel Hankins
- Harrison, Arkansas


(2005)

A. Mr. Hankins in completely correct - a deox step is necessary after the etch and prior to the anodize. I've become so accustomed to the two baths always being used together that I just think of it as one process, hope it didn't cause any confusion.

Good luck.

Jim Gorsich
Accurate Anodizing Inc.
supporting advertiser
Compton, California, USA


Effect on surface finish of flash anodize

April 27, 2018 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Great intellectual space, people. Thank you all.
What is the effect on surface finish to reverse flash the rack prior to anodizing? Are there any current/time parameters for this action?

Martin Gaudet
- Bainsville, Ontario, Canada



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