I been using fast etch on a hood i am trying to clean up. I have used it on some welds before with good results where after it dried it left a white looking coating. On my hood after it dried it left a bright brown rusty looking color mixed with white. Is this normal? I hit it with my wire brush and it did rub off rather easy without to much labor. Also when I rub it with my finger it smears but that might just be the white residue smearing over the brown.