Figuring out current density

[SX Paintball]

I have a 14 volt 25 amp rectifier, so my question is how do you exactly figure out current density with an adjustable rectifier? Say I have a 1 sq. foot piece of aluminum, would I turn volts all the way up to 12 volts and then turn up the amps all the way and see what the max amps are, and that is my current density?? I have not checked my current density with this rectifier, becuase I was unsure how to. With my old battery charger it drew roughly 6-7 amps with 1 sq. ft.

Thank you,
Shane

[acidrain]

Yeah, this is a common question for beginners...
YOU pick the current density.
I say go for 6 amps per sq. ft.
Calculate you surface area.
Use the 720-rule calculator (in the sticky at the top of the page), and enter the surface area, your target CD, and how much milage you want (go for 1mil for black, red, and dark blue, .75mil for medium colors, and .5mil for gold, copper and clear). It will tell you how long to run it, and the amps.
Turn you volts all the way up.
Turn the amps all the way down.
turn on the power sourse and slowly turn up the amps until you get the amps you want.
The volts will do whatever it takes to maintain the amps.
Make careful notes. Make a chart with two colomns... one for volts, the other for temperature with a time start and end. I made mine on a dry-erase board right next to a clock.

start time: end time:

amps:

volts: Temperature:
start
05min
15min
30min
45min
1hr
1hr 15min
1hr 30min
1hr 45min
2hrs

[SX Paintball]

O.K. that is what I have been doing ever since I got my rectifier. Just was unsure if I was doing it right. I want to get a better understanding on my entire anodizing process. I really want to thank everyone here, and especially Acidrain for all the great information.

Thanks again,
Shane

[sswee]

With a 14V25A PS you may need to drop to 5 or 5.5 ASF. The 14 volts calculates to a max CD of 5.6 ASF. Depending on your setup, tank temp, aluminum content in the electrolyte, you may be able to get away with more but I would start out at a 5A CD and see what the peak voltage is for a run. If you go too high on the CD to start with, the PS will run out of voltage needed to push the set amperage. Run time for 1 mil at a 5A CD will be 144 minutes.
SS