Distance to cathode

[PeterM]

Hi
How much importance does the distance-relation between anodising part and the cathode have?
Should ~18 cm between a ~2 square centimeter part and a ~80 square centimeter cathode be enough?
The reason im asking is cause atm im having a really little plastic tank, all my parts are small. Now and then i get bad anodizingresults > White chalky surface that dont seem to be scratch-protective. And strange darker stripes. Could this come from too little distance thus resulting in the part getting chalky and pitted as its stated in the LCD-manual?
// Peter

[M_D]

It (distance) definitely affects the anodizing to certain extents. It doesn't seem to be a critical issue, but you should keep at least 3+ inches (7 to 8 CM ) distance between the work pieces (anodes) and cathodes. With the distance you have, I doubt this issue is your problem, although I have been wrong before.

The white chalky layer that is easy to scratch off sounds like disoultion is to blame. That's where the anodized layer isn't built up properly, or is damaged at some point in the anodizing cycle from the acid. There are various degrees of disolution, from mild to obviously bad.

Your methods may be faulty, and one or more of the following may be to blame: too high of a tank temp, wrong acid concentration, bad connections, wrong current density, and wrong anodizing time are all possible reasons you are seeing problems. To a degree, there is some latitude on some of these parameters, but you still have limits to stay with in, and depending on some of the primary factors the other factors need to be inline. In other words, you have to have a relatively well balanced system. Without knowing any more of your system, that's about all the help I can give.

[PeterM]

Thank you M_D
Atleast i can focus on other parameters than the distance then to find the problem.