I use an E-tank and it does a fair job at breaking down rust, however i have noticed that it tends to leave a black almost powdery feeling residue. I use dawn, white vinegar, barkeepers friend, magic eraser, more dawn, steel wool, and green 3M all in separate stages. I get to a nice grey surface but 2 minutes later it is a bull black again and generally has a much more metallic odor during seasoning cycles. Is this a normal reaction for cleaned skillets with rust issues?