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Student anodizing

I do sulfuric anodising. I am using plate aluminium 1100 and I just use buffing method to clean the surface of aluminum. I am using 1 mol sulfuric acid and 14 - 16 voltage for the process for 50 minute and aluminium welding electrode to hanging the part. When I run the process, the part did not anodize perfectly, and the part have pitted. why this problem occur. I want use current density 1 A/dm2. how to measure the current.

Zahid
asa - Malaysia
2005

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2005

You need to put an appropriate ammmeter in the circuit to measure amps. You also need to calculate the total area of the part. You might not have enough cathode area. It should be about 1/3 of the part area. Mechanical polishing is rarely adequate for proper cleaning and in some cases is detrimental.
1 mol sulfuric acid is too weak. You need a 15% by weight sulfuric acid / distilled water mixture.
You need a 1.3 A/sq DM for good anodizing.
1100 does not require desmutting after an etch step as it does not have any alloy metals to smut, but it does need a deoxidizing step for proper coating.

James Watts
- Navarre, Florida