What do I need to..............

[00_buckshot]

grow a type II coating of 1 mil using LCD andodizing?

[Fibergeek]

Excellent question.

That's something I'd like to do too, and for the same reason as yours. Except mine hasn't the pedigree yours has (preban Colt).

Well, I'd guess 6A/sq.ft., forced electrolyte cooling to retard dissolution, very long anodization time, and maybe a chemical additive to further retard dissolution and/or promote a more favorable anodic structure(?). I've been reading about some of these additives, I don't understand it well enough yet to be willing to talk about it.

It would be cool to do.

[00_buckshot]

Fibergeek,
I can't remember where you live but what is your opinion on using cold winter air to help cool the bath to an acceptable level? I live in Montana and have an unheated attached garage on my home. On average without my baseboard heater on it will maintain about 45 deg. F with the door closed. If I open the garage door it only takes a little while to cool the interior of the garage down to roughly the outside air temperature. If you used a large enough bath combined with ambient cooling(?) you could attempt hardcoat anodizing. I'm curious to know more about solution additives as well. From what I've read it sounds like retarding the dissolution is the biggest difference between hardcoat and Type II.

[Fibergeek]

I haven't heard of ambient air cooling working too well. The problem is the heat must be moved from the work to the electrolyte, and it needs to happen quickly. This is the only thermal interface where it does any good. The thermal path from the electrolyte to the ambient air isn't very efficient (air is an insulator). Having a very large electrolyte volume for the work should help however.

Type III anodize (hardcoat) also includes a higher density coating (smaller pores). This will also need current density in the 24 A/sq.ft. range for real hardcoat.

The 1 mil thick Type II coating you describe is sometimes called "Type 2 1/2" by some anodizers, as good a name as any.

[NeoMoses]

If you use the ambient air to cool your electrolyte tank to a low temperature and you have sufficient volume in the tank, it should work. Your tank temperatures shouldn't rise much more than usual, assuming you are using 6 A/ft^2. Water has the great ability to absorb much heat without a large change in temperature (specific heat).