Green rust = copper?
 

I am taking care of a large tank. I found out on day 1 the ATO is just running straight off a copper line into the tank. I have turned off the ATO and have been manually adding RO/DI water until the new tunze ATO arrives. My question was, I noticed the metal arm of the float valve for the ATO has some green rust on it. Does that mean this piece is either made of copper or is a copper alloy?

Green corrosion indicates copper-based material :surprise:

And pretty much only copper right?

I guess that is why they have not had much luck with inverts to this point.

Copper-based includes brass and bronze
Silver- and chrome-coated copper-based material will also do this if the coating is compromised
Regardless, it's not good
Might be hard to get a reading, but it wouldn't hurt to run a copper test

I might run a test now that you brought that up. Thanks.