Hi Greg, id you make it all the way down the thread? The post I was refering to was Re: Stainless electrodes
Posted by: larry rusch -- Friday, 27 February 2004, at 3:29 p.m.
This was nearly to the very bottom of the thread. What I meant by convincing is that this gentleman seems to be knowledgable. His post is copied below. Here it is in full:
Briefly, concerning hexavalent chromium. In any electrolytic cell there are basically two types of chemical reaction occuring; reduction at the cathode and oxidation at the anode. What this means essentially is that the anode (the so-called sacrificial electrode) dissolves. Electrons are removed from the neutral metal of the anode material and it goes into solution as positively charged metal ions. In the case of stainless steel (at least most of the common ones) there is substantial chromium present in the alloy. Chromium exists in primarily 2 ionic states in solution, +3 and +6, trivalent and hexavalent. This means that either 3 or 6 electrons have been removed from the neutral metal atoms during the oxidation process. While trivalent chromium is relatively benign, hexavalent chromium can be rather nasty, especially at high concentrations. It is also carcinogenic. Under most electrolysis conditions the amount of hexavalent chromium generated is small so the acute effects are not generally a problem provided one takes normal precautions when dealing with chemicals/solutions. Disposal of the solution is more of a problem however, because hexavalent chromium is a highly controlled environmental pollutant and must be controlled down to very low levels, much lower than you might see in a used electrolysis bath. There are ways to reduce or even eliminate the production of hexavalent chromium by adjusting solution composition, current, voltage, passivation techniques and so on, but it gets complicated very quickly. But, why bother? The aim here is to clean old iron. It's easiest just to avoid the problem by not using stainless steel for your anodes. Concerning acute effects, these are highly individual, I know people who worked up to their elbows in plating solutions for years with no ill effects. Then all of a sudden one of them became sensitized so severely he couldn't walk through a plating room without breaking out in a rash. This was a nickel sensitivity, not chromium. I hope I didn't bore you with all of this, but I wanted to try to give an understandable explanation without giving a course in chemistry at the same time. Hope this helps.
