Current Denisty Comparision

[mtarrant]

Has anyone done a controlled test of the same part at different current denisities as calculated by the 720 rule.

I am using 5 A/sq ft on a 28 sq inch part for 100 minutes and resut is pretty good. I would be interested if anyone has tried lower (say 3 or 4 A/Sq ft) and higher (6,8, 10 A/sq ft) with corresponding change in anodizing time with any ill effect.

One problem I do have is producing a current much more than 1 amp. My power supply can generate constant current up to 2 amp at 16 Volts but 16 Volts won't push more than 1 amp through the acid tank. This means path resistance of 16 ohm. Wire to part resistance measures < 0.5 ohm so the rest is conductivity of the acid (or lack of it). The acid is quite old (over 10 years) but has just been stored all that time. Tank is 7 ltrs (2 gal approx) about 12x8 inch, and has a lead sheet along the bottom and up two sides for a cathode.

[sswee]

I started out using a 4.5A CD, battery/battery charger w/light bulbs in a 2gal. bucket and watching for par. Since then I have moved to a 20 gal tank, 3A and 20A PS, and the 720 rule. I have tried 3A to 8A CD on identical parts using the 720 rule. Most parts were run for 1mil coating thickness. At 3A, it took a long 240 min. I had no noticable differences in the parts between the different CD's except shorter run times.

If your PS is limited to 16V, then you'll be limited to 6A CD if everything is good. If your acid is that old, it probably needs changing.