1st run with immersion elements. Brown/black coating?

[aj]

Well, I did my first immersion run this past weekend, and it was a tremendous success. I have two 1" SS half-couplers TIG welded to an old Killians keg, one 3000W (@240) element, one 1500W(@120) element, and a homemade control box with switches and plugs for both (pictures soon).

At the beginning of the run, I flicked them both on, then I killed the 1500W element about an hour into the run, leaving the 3000W (a.k.a. 750W @120) to finish up the remaining 20 minutes or so left to boil.

The run went beautifully. Afterwards, however, I noticed that my heating elements had taken on a black finish with some brown areas as well. I've taken one of those green abrasive kitchen pads to them and gotten off anything that wasn't oxidized on, but they're still pretty dark, and I wanted to know if this was considered normal and just leave them as-is, or if I should try and sand them down or something.

[Bohunk]

AJ, I had the same thing happen to me when I first ran my boiler. First the element turned dark brown, then agter a couple runs it got more of a reddish color, then finally the element turned a bright clean copper color. I worried about the color, thought my element was burning up, but it finally did settle down. My element is copper, and had a bright tin plate on it when I bought it. In my case there was nothing to worry about, I just let it do it's thing.

The Bohunk

[hornedrhodent]

one 3000W (@240) element, one 1500W(@120) element,

Are the both the same element?

[aj]

No. I'm referring to them by their labeled rating. The 1500W is rated for 120V, so it's 1500W when at normal US wall voltage. The 3000W is rated for 240V, so it's 750W when plugged into normal US wall voltage. That was the idea. My stillhead is rated at about 750W, so I use both to bring it up to a boil, then I turn off the 1500W.

[dog1976]

When I built my boiler I used a stainless steel milk can and 2 stainless steel water heating elements. I did not want electrolysis do to dissimilar metals.

[aj]

Would you be so kind as to clarify a little? Are you saying that this is what's happening to my elements or what? I was told there would be no electrolysis between these elements and my SS boiler.

[dog1976]

I am not an expert on this. When you have 2 different metals in a non neutral solution electrolysis can occure. Water heaters use a sacrificial anode. There are a few chemists on this site maybe they can put a little more light on this subject.

[markx]

The alternating main voltage sometimes induces eddy currents in the boiler's walls and the contents. These tend to cause electrolysis and corrode the boiler. If you connect a sacrificial anode of active metal (eg. magnesium) to the boiler it polarizes the system permanently so that the boiler is under cathodic potential and therefore the eddy currents have a hard time trying to dissolve it.