Quote:
Is there any copper in the loop that touches water and the nickel? Under standard conditions the nickel can have a tendency to oxidize (so your nickel may be pitted). also, metal oxide formation may possibly be promoted in the water. Copper oxides tend to be red or black (but other copper compounds form a blue-greenish color); nickel oxides tend to be greenish (more so than coppers).
EDIT: http://www.jim.or.jp/journal/e/pdf3/50/11/2557.pdf
Basically, they point out that copper in steel can form "green rust" especially if the water happens to be oxygenated.
EDIT 2:
One way to help the situation is to prepare your distilled water by heating it to near boiling for some time. Then let it cool down. This will produce reasonably oxygen-free water as long as you get it into your loop soon after cooling.
Edited by Quantum Reality - 5/6/12 at 12:09pm













