acid ratio when anodizing alum

[john]

When using lab grade sulfuric acid what is the best concentration? I\'ve seen 15 to 20 % and other places i\'ve seen it should read 1100 with a battery acid tester?

[mcaswell]

33% acid, 67% water.

Specific Gravity: 1.26

[john]

Wow i didn\'t think you would won\'t that strong of a solution..Presently have a 20 gallon tank with 2 gallons of acid to 18 gallons of distilled water.Won\'t a higher concentration of acid eat the parts away?

[mcaswell]

No reports of dissolving parts have materialized yet

This is a standard acid concentration for sulfuric acid anodizing baths.

[mcaswell]

IMPORTANT!!!!!

We are talking about BATTERY ACID 33% concentration here, not the 'LAB GRADE' or 98% reagent grade.

[dropride]

in the manual it says you have to mix battery acid with water, that would bring the specific gravity way down wouldnt it, by what your saying is adding water isnt necessary then?

[Fibergeek]

Caswell is saying that the electrolyte is 1 part sulfuric acid and 6 parts distilled water. Automotive battery acid is 50% sulfuric acid and 50% water. The electrolyte can be made by mixing 1 part battery acid with 3 parts of distilled water. It can also be made by mixing 1 part of reagent grade sulfuric acid with 6 parts of distilled water. I have no idea what the specific gravity would be, and I can't see why anyone would care, we're not making a lead-acid battery here, the actual concentration is not critical.