I still haven't had a chance to try it (we seem to have run out), but as soon as I can get my hands on some again I want to add a small amount of Sodium Metabisulfate to my coolant (which is currently distilled water and water-wetter)
I'm very slowly getting either a thin white film forming on the insides of my tubing, or the coolant itself is getting slightly cloudy, I can't tell without draining it (which I don't want to do, though I suppose I will have to when I finally decide what to upgrade to and rebuild my system).
Anyways, this chemical is used primarily (in my experience) to sterilize home-brewing equipment before use. In the strengths we use it in for wine-making, it has a fairly strong smell (though less than water-wetter) and will sterilize anything it comes in contact with in under a second - this is using it at saturation (there is still solid stuff sitting in the bottom of the storage bottle). Research with google shows it to be both a bactericide and an antioxidant, but I can't find much more than that. I'm hoping that adding just a small amount to my coolant will prevent growth, while not smelling too bad (though my system is sealed to the point that I can pressurize it to a low pressure, so there is no evaporation, I can't even smell the water-wetter).
What I worry about is it will react with the water-wetter itself. It is used in brewing, so it should be safe with the copper/brass of WB's/rads as they also use many copper/brass fittings, and I use chem-grade Tygon which is pretty much invincible. We store it in an old plastic milk-jug and it didn't eat that, so the pump should be ok. But if anyone who has the resources to do these tests with putting a few pieces of acrylic/copper/etc. into a tub with a coolant mixture for a week or two is testing various coolant mixtures again, I'd love to see some of this stuff added to one and the results posted up here.
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