I went to do a boat yesterday the customer said it was oxidized pretty bad. When I got there the oxidation wasn't bad at all. What he thought was oxidation was the waterline and down. It wasn't that brown nasty scum but I acid washed it anyway and it was still there. I used Makita rotary and wool pads with marine 31 heavy oxi remover and it hardly touched it. Then I sanded the hell out of it with 1000 and buffed again. sand then buff then sand then buff then sand then buff. When I got there it was solid white now it is blue like it should be but you can still see the line where it was. WHAT WAS THAT and is there something else I could have done?