Lost connection and need to re-anodize same part

[mracer]

After reading countless posts and the LCD Ano manual, I decided to do my first run but lost the connection after 15-20 min. I had tapped a M3 hole in my part and threaded my aluminum anode into it, but the connection was to loose and the wire must have anodized.

After 20 minutes in the ano bath at 1.5A (6 ASF given that my piece is 1/4 Sq. Foot), I lost connection when I air agitated the part. I knew something was amiss from the get-go when I the initial voltage read on my CC PS was in the vicinity of 15-17 Volts. I immediatlely suspected a poor connection, and after air agitating, I could not muster any amperage at all.

My question is: how to go from here? Do I need to strip whatever layer that has seemingly anodized in that 20-minute span (have not idea of the thickness) using the Caswell stripper product or can I just re-start the ano process with a better connection as if nothing had happened?

Note that my connection this time will be improved by adding an aluminum nut fastened to the wire and a better tapping job. I am planning on switching to titanium wire in the future so the anode does not anodize, but for now I am restricted to using alu.

Thanks in advance.

Patrick

[sswee]

You'll need to strip the part and start over from the beginning.
SS

[Countryboy1966]

As far as the high voltage reading, someone correct me if I am wrong, but it takes more amperage to anodize a small part versus a large part because of the difference in surface area. I might be right or wrong, but the point I am trying to make is make sure you understand the voltage to surface area relationship before you start over again as maybe I should too . I've found when I loose connectivity, my amperage continues to increase then flips to CV.

[sswee]

It takes the same current or amperage per square inch to anodize without regard to part size. The larger the part, the more surface area, the higher the amperage setting to run the part.

On a CC PS, if you loose connection, the amperage should maintain the setting until the voltage maxes out. Then the voltage will stay at max output and the current will decline.

The voltage has little relation to part size or amperage setting. It is directly effected by the current density used and the circuit resistance as per ohm's law.

A similar situation will arise if the surface area of a part is miscalculated smaller than it actually is. This causes the current density to be higher than desired. If the miscalculation is off by too much it will max out the voltage on the PS and cause amperage to drop.

In example. I have run parts from a few square inches total to parts of two hundred square inches. The set amperage is much larger on the large parts but the voltage used on the different runs is always the same provided I run the same CD, have good connections and tank temp is the same.
SS

[mracer]

Thanks Sswee and Countryboy for your expert advice/interest:

I just received my Anodizing Stripper from Caswell in the mail (wow, next day delivery in a different province!). The instructions simply state to dip the part and test for connectivity. Is there anything else I should be particulalry careful about? I cannot find that many posts on the use of the anodize stripper in the forum.

I am being extra careful as it is a nice part and I do want to cause permanent damage. I also want it to exactly match the finish of another part that will be ano'd and dyed the same colour (and that part will not have gone through the stripping process, hopefully).

After removing the anodize film, I plan on re-sanding up to 2500 grit and polishing with rouge/green compound, degrease in SP, anodize, then dye in Fast-Blue to get a slightly glossy finish. Are my hopes realistic given that this part will have been stripped?

Also, do I need to de-ox/de-smut again? I did it previously and wonder if this would be overkill.

Thanks, I am very appreciative of your guidance for this first ano project!!

[sswee]

The time to strip will vary with the amount of coating and its structure. It is best to check the part about every 3 to 5 minutes. You should be able to judge how it is doing by the color and how even it is. You will need to strip past the color to get the base of the coating. The aluminum will take on a gray color from smut. The gray smut should be evenly colored on the part and will vary in color dependent on material grade. IE: 6xxx aluminum has a light to medium shade of gray. Some grades turn almost black. Acidrain has some excellent posts on telling aluminum grade by the color of the smut.
Yes you will need to deox/desmut after stripping the part. The part should come out of the desmut new aluminum color. Almost a white.
It should be like starting with a new part that has never been anodize when you finish provided you do not forget the part in the stripper and leave it in too long. When I started and was using aluminum wire to rack, I put some 1/8" alum. wire in to strip for another run. I forgot them and when I remembered the next day, I pulled them out to see that the only thing left was what was out of the stripper.
SS