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White streaks in anodizing due to uneven blasting?
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To Whom it May Concern:
I am anodizing per Mil-A-8625 [link is to spec at TechStreet] 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
Anodize Shop Manager - Chino Valley, Arizona, USA
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This is VERY simple, follow this instructions :
1) etch on your caustic for 10 sec
2)20 sec deox
3)aprox. 45-60 sec in ABF sol.
4)flash anodize for 10 min.
5)GO BACK TO YOUR CAUSTIC ETCH, STRIPPING THE ANODIZE
6)deox the same than before 20 sec.
7)go back to your ABF sol same time
8)anodize for normal time w/your die and seal
And thats how you get rid of the streaks from any blasting
Sergio G.- Oxnard, California
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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 striplight , even beadbast and anodize.
Good Luck.
Bill Grayson- Santa Cruz, California