Thread: Black Coating

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I noticed while trying to get the rust off my car their is a thin coating of black stuff, is this the zinc oxide? Do I have to get that off before I start filling and primeing with the etcher? I don't want to go too far, that metal is thin enough. I'll post a picture later.

Sean

you want to sand that up abit with 36 grit or 40 i use a da so you do not over work the steel and make it to thin you want to sand it any were you are going to do alot of filling with body filler or epoxy the body and go over the epoxy primer with filler i do not like to do that much but can be done that way to you can get a stack on and have shrink marks in the finsh to many over lays of stuff less is better

Thanks again Pat,
so if the sandblaster doesn't want to take it off (I'm using a cheap siphon feed but it's doing pretty well) then I should just scuff it up not try to sand it right out? Then I'll get on with the body filler.

Thanks,
Sean

yes you just want to sand it up abit 36 or 40 at a slow speed on a DA work the best then fill if deep i would use a glass filler like mar glass them a body filler over that make sure you sand your mar glass good before top coating with your body filler

Thanks Pat, I'll go snap a picture just so you can see.

Sean

Here they are, you can see it just looks like the metal is burnt with a torch but is smooth to the touch. The top left of the second picture shows best what I mean.

Sean

go over the car with a da with 40 grit and with a 6 inch sanding paper is what i like then wire wheel or blast your pits then fill then top coat them spots with primer the every thing can be metal prep or do one panel at a time metal prep then sand were the filler needs to be then fill and sand and prime a panel at a time any thing that can be laid flat like doors on saw horse helps you want to cover the panel up with primer to seal out moister the cleaner the steel the faster it will rust you need use a da or a sander with a bigger pad looks like your using a 3 inch rollock wheel ?

LOL they're 4 1/2" Scotchbrite wheels on my grinder, I tried to find those 7" purple 3M Strip-it discs but no luck. I need to take a break between sandblasting, I don't want to kill my new compressor.

http://www.houseoftools.com/product.htm?pid=15742

I figure that should be enough for painting, sure is quiet too. I think it puts out 18.5cfm at 100psi, I don't know where I got that idea .

Sean

them wheel will put heat in the steel and could warp it they will just buff up steel that is rusty you need to cut the oxide off the steel with out making the steel to thin. what you are seeing that black is the 3m wheel buffing up the rust