Im using the salt water and a 6v power source at 2 amps method. for the metal im using just plain old steel allen wrenches. I get non magnetic iron oxide but on the positive end of the allen wrench and shell of magnetic steel forms that is black when in the water and when dries it rusts. what i want to know is does this stuff count as iron oxide? I don't think it does because as how i understand iron oxide is that it is suppose to be nonmagnetic. i can figure out who to either prevent the black shell of stell from forming or a way to filter it out. can anyone here suggest a method?