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Defect in shiny anodized product
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"Aluminum How-To" -- Chromating, Anodizing, Hardcoating by Robert Probert (2005)
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"The Metallurgy of Anodizing Aluminum" by Jude Mary Runge (2018)
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"The Surface Treatment & Finishing of Aluminium and Its Alloys" by Wernick, Pinner & Sheasby (1959 - 2001)
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"Surface Treatment and Finishing of Aluminum" by Robert King (1988)
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"Anodic Oxidation of Aluminum and Its Alloys" by V. F. Henley (1982)
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"The Technology of Anodizing Aluminum" by Brace (1979)
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"Aluminum Finishes Process Manual" by Reynolds Aluminum (1973)
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"The Anodic Oxidation of Aluminum" by A. Jenny (1940)
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"Anodizing and Coloring of Aluminum Alloys" by S. Kawai (2002, VERY RARELY avail)
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Q. I have a problem in shiny anodized product -- appears on surface after cleaning and polishing.
Cold stamped aluminum, then mechanically polished, and then transferred to the anodizing line
degreasing
HNO3 (50-60 °C)
polishing (85% H3PO4, 15% HNO3, 110°C)
desmut
anodizing (15 min, 20 °C, 190 g/l H2SO4)
staff - nam dinh, Vietnam
May 4, 2022
A. What is the alloy? Heat treated? Suspect Chloride contamination from the water, or iron drag into the anodizing from the deox.
Robert H Probert
Robert H Probert Technical Services
Garner, North Carolina
Q. How is the iron concentration in the deoxidation tank and in the anodizing tank analyzed?
S Llinares- Spain
November 27, 2023
Q. I have a similar problem on the bright anodized product. The top of the parts has a defect that does not go away when rubbing. The defect appears more in the upper rows of the rack and always on the top of the pieces. Sometimes it also appears on the sides of the rack. It appears before anodizing.
Our process is:
We use alloy 5657
bright dip (H3PO4, HNO3 and H2SO4)
deox (diiron trisulphate, sulfuric acid, nitric acid)
anodizing (195 g/L, 20 °C, 17 min)
- Spain
November 16, 2023
A. S Llinares
It looks like the Brite Dip solution is drying on the part(s) prior to rinsing. Consider a faster transfer to the rinse, or add a spray rinse over the Brite Dip tank. If you are operating the BD at >100 °C, water added via rinsing should boil off in a timely manner.
- Green Mountain Falls, Colorado
November 19, 2023
Insightful answer, Willie. I bet you're right.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. Thank you. I will try adding a spray rinse over the Bright Dip tank.
I have read that you can increase the wetting additive in the Bright Dip, do you know what wetting additive to use?
- Spain
November 20, 2023
A. S Llinares:
We used an R5 Bright Dip many years ago. No additives required other than seeding with a little copper. I am unaware of any wetter you could use. Sorry.
- Green Mountain Falls, Colorado
November 21, 2023
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