Letter 42837

Relationship between thickness of oxide layer and time/ voltage for anodizing Al-Alloys [Pakistan] 

October 28, 2006

I need the graph of the relationship between thickness and time/ voltage for anodizing Al-Alloys.

Muhammad Bashir
GIKI - Topi Swabi, Pakistan

The graph is dependent on alloy as well, and is available in the "Surface Finishing and Treatment of Aluminum and Its Alloys" book noted in the recomended books section of the homepage of this site.

I don't have an electronic version (and, I'm sure its copywrited anyway), sorry.

You don't need the most recent version, by the way, the second to last version has the graph also (and possibly earlier versions as well) and can be bought used for significantly less money.

Good luck!

Jim Gorsich Accurate Anodizing Inc. Compton, CA, USA

Thickness vs. time at constant current density, electrolyte concentration and temperature is usually reported.

>From 'Anodizing Characteristics of Commercial Aluminum Alloys in Sulfuric Acid,' G. H. Kissin et al., pages 13-31 in The Finishing of Aluminum (1963):
The anodizing rate for wrought alloys 1099, 1100, 3003, 5005, 5052, 5357, 6061, 6063, & 7072 is ~0.405 micron/minute (15 wt% H2SO4, 12 Amps/sq. ft., 20°C) for anodizing times to ~90 minutes. Slightly lower rates for longer anodizing times (>60 minutes) and higher temperature (25°C).
Slightly higher rates (0.41 micron/minute) for Al 4043 & 4343.
Rates for 2014, 2024 & 7075 are lower, especially at the higher temperature (25°C) and longer times (>40 minutes).

The voltage necessary to maintain the current density of 12 Amps/sq. ft. is shown as a function of time for the above alloys (at 15 wt% H2SO4, 25°C). The voltage increases roughly 5% over the anodizing time of 5 to 60 minutes. Lowest voltages (13-14 V) required for 7072, 5052, 6063 & 7075. Highest voltage (18-19 V) for 2014.

'Effect of Voltage During Anodizing of Aluminum,' by W. C. Cochran and F. Keller, pages 104-126 in the same book may be of interest. Voltage, sulfuric acid concentration and anodizing temperature were varied. Coating weight, abrasion resistance and clarity are reported for Al (99.99%) and bright anodizing alloys including 5357, 5557 & 6463.

Please post any measurements on-line.

Ken Vlach - Goleta, California

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