Peak voltage ?

[R-Wells]

Hi M_D,
My lillte brain says that temp has to be higher on the surface of the parts,
At the moment I am playing with everything, trying to learn.
I am using air to circulate, I started of with aqaurium pumps, now I am using shop air .
I am wondering if there is not a way to eliminate all or most of the variables you mentioned.
For instance, could we measure the resitance across the electrolye at a given temp.

Rusty

[R-Wells]

Hi ,
I didnt finish the last post, I had to go take my pants off, a spyder crawled up my leg

I did notice a volatge increase when ading more air to my circulation,
So I have to believe it is from moving the hot electrolye away from the part.

Rusty

[Fibergeek]

You're right as usual, M_D.

The big, fat hint I dropped several times (the temperature in the pores, not in the electrolyte is what actually counts) wasn't lost on M_D, and Sswee I suspect.

You can see this if you study my anodization curves (1 through 3). Pore temp is obviously difficult to measure (but possible, its been done) all we can do is measure electrolyte temp. (better than nothing).

The best case is to have the anodization curve slope unwards as the anodization progresses, I was able to achieve that with 6xxx and 1xxx alloys. 2xxx and 7xxx alloys showed a downward slope anodized under the same conditions. The closer you can get to an upward sloping curve the better, difficult with 2xxx and 7xxx alloys.

This Spring (its Spring here now) I will start another series of controlled anodization experiments; looking deeper into cathode area and into the use of electronic feedback (a "smart rectifier") I will design to automatically correct down sloping anodization curves. I will look at Ti racking effects in more detail too.

(edited for spelling)

[M_D]

Well that wasn't hard for you to figure out. There is a boundary layer that forms since the heat comes off the part, and even with mild agitation it is still significantly warmer on the part surface. Assuming your electrical and mechanical connections are robust and aren't hanging on by a hair, you can demonstrate how it changes by wiggling or swishing the part around and watching the voltage. Unless your tank is exceptionally well agitated, the voltage should go up immediately as the boundary cools down, and it will start to drop as soon as it begins to warm up. With LCD the temperature difference will be less between the boundary layer and general or average tank temperature, which is one of the many reasons it is well suited for hobbyists.

This may have been slightly off topic, but I guess the point I was trying to make is that comparing voltages is tough unless all factors are controlled to the same value.

[R-Wells]

No M_D, it wasnt of topic at all.
Thanks guys

Rusty

[M_D]

I started the last post before I knew Fibergeek posted, I just wanted to say I will get some Ti rack tests done soon hopefully. I got so tied up I had no time to do it properly.

Soon after I first began anodizing I noticed the phenomenon of voltage fluctuations. For instance if the power was cut, or the part lifted out of the electrolyte momentarily and then was power reapplied to the part, the voltage would go up for a while and then settle back down. Also, if I wiggled the part around while it was anodizing the voltage would go up. At first I thought it was the connection failing, which is a possibility if it isn’t good. But I knew that the connections were good, and there was another cause.

Anyway, it is one more key to fully understanding the factors than come into play when anodizing that I’m glad to know.

By the way, it's spring here too (at least spring like weather).

[Fibergeek]

Spring in the mid-atlantic is cold than immediately in the mid 80's, in one day's time. Not much of a Spring.

Like M_D says; don't get hung up on voltage measurements, it will backfire on you if you don't understand what you are looking at. Current never lies.

R-Wells, chew on what was said for a while, you will have questions.

I'm stepping out of this thread. You guys have everything under control.

[sswee]

Thanks Fibergeek and M_D for the input. I am crystal on pore temp relevance, just hazy sometimes on organizing thoughts and conveying what I want to say. I've been playing with part position in the tank until I can do something better with cooling and circulation.

[R-Wells]

Hey sswee,
I understood you , I just didnt make myself clear that I wanted to discuss theory.
For your info, my little AC unit is doing a good job at the moment.
I have run two 2.4sqf parts back to back at 4.5asf with no more than a 2° temp increase. ( start at 70° finish at 72°).
Yesterday I ran 4 parts (aout 1.4 sqf) at 6asf back to back at 70° with no temp increase at all.
I kinda figure this will change as summer gets here and the ambient temp goes up another 20°.

I was runing two fairly big aquarium pumps, when I changed to using the shop compressor i saw a immediate increase in voltage of 1-1.5 volts.

Rusty

[sswee]

I haven't had time to get to Home Depot yet. Did you build a box around your tank?