[greenmoonshine]

I have been outside for the last 3hrs sanding the roof of my car so I can lay down epoxy primer on it but I cannot tell if its ready for it yet or not. I figured that I would just sand it down to bare metal and primer it so later I can go back and use a little filler where needed but I have been sanding for aprx. 3hrs and its not down to the bare metal but it has a blackish tent to it along with little spots of rust that just looks as if there stained in. I first started off with a knotted wire wheel on an angle grinder then moved to 60grit sand paper on an electric palm sander but it still just looks black.
Here are some pics and any input you can give would be MOST appreciated as I am on a limited time frame but also dont want to ruin it. I also thought maybe there was some old factory primer that I just cant cut threw so I sprayed a Test section with some Aircraft paint stripper and let it set for 15 min to see if it would lift anything..........nada, not a damn thing, so I am a little confuse

This is a pic of what I started off with


and this is where I am at



here is a close up

again any help is most welcome
Thanks
GM

[Pontiac_Judas]

I am not an expert (they will be along, I am certain), but that looks like a form of corrosion to me. Sometimes the steel "blackens" instead of the usual orangish rust (or is a mix of both).

Im guessing you will need some kind of rust neutralizer/converter before painting, but please wait for others to chime in.

[adantessr]

You need to get a D/A sander and some 80 grit discs to get through that stuff . It'll go much faster than what you've been using also. Trust me . I stripped a '52 Mercedes back in '85 with a D/A sander . It didn't take all that long, and it had several coats of paint .

[V8&4spd]

If you put some phosphoric acid on there, it will loosen up any loose paint and it will remove the surface rust if there is any. Leave it on there for awhile and you can rinse it off with water. You can put the epoxy primer on after.

[greenmoonshine]

I have a small 6" D/A sander but its broke. I have some week Hydrochloric acid but I think it will actually eat the metal itself, so I dont think I want to go that route.

[V8&4spd]

Phosphoric acid before and after.

[greenmoonshine]

I found some of that Klean strip acid etch at homedepot http://www.homedepot.com/Paint-Clean...atalogId=10053
its only $15 but not sure if chemical is the way to go. I do have a homedepot near me so if this is what needs to be done then this is what I may have to do. I actually took vacation from 1 job so I can get this done before the snow and cold gets here so its almost a must.

[V8&4spd]

They sell it under a few different names. The stuff I use is green. It works, I have already done it and the paint has been on for years. It says you can use body filler over it also. It kills any surface rust. It takes a while for any rust to reapear when it's left out in the elements without any primer put over it.

[greenmoonshine]

Originally Posted by V8&4spd

They sell it under a few different names. The stuff I use is green. It works, I have already done it and the paint has been on for years. It says you can use body filler over it also. It kills any surface rust. It takes a while for any rust to reapear when it's left out in the elements without any primer put over it.

I called my local homedepot and they do have it in stock, in the description it doe's say that it inhibits flash rusting so thats a plus

[V8&4spd]

This is a frame before and after. It was only on there less than 2 hours. I had it rained on and it did not rust. It will get surface rust on again if left unprimed but it takes awhile.

[greenmoonshine]

I guess my only concern with the klean strip prep/etch is, will it take off the black? I believe that may be an old rust converter as it looks to have brush marks in it, but whatever it is, the Aircraft stripper wouldnt even touch it and that stuff is strong. I used it once to take undercoating off and old gas tank that was covered with the stuff, it ate through it with no problems.

[V8&4spd]

I pour it in a jar and brush it on with a paint brush.

[deadbodyman]

Its hard to tell but it could be a few things..it would help to know how old the car is...
You should try the stripper again in a small spot, put a thick coat on ,pour it out of the can and make a little puddle about the size of a soft ball, let it sit 30 min,then scrape it off with a razor scraper ,it might come off clean. It could also be old lacquer primer ,in a very (small pitted ) (sandpaper) like surface that your not getting deep enough into ,sometimes a wire brush or wheel works with the stripper try the same thing to see if it softens it enough to get it off with a razor scraper,the razor is the key and you'll need a whole box of them...
as far as the acid goes use only phosphoric,be careful and pay attention to what your doing ...I prefer Ospho because it doesnt need to be neutralized.everything you need to know (pros and cons) about it is on a thread called "the Ospho solution" complete with videos and step by step proceedures...
...Heres a couple short vids on stripping (paint stripping ) http://www.streetfire.net/video/chem...xy_2053679.htm

http://www.streetfire.net/video/usin...-2_2050902.htm

[JohnnyK81]

I always wonder if that prep is necessary. The epoxy should seal out all moisture. Rust will not keep on going without oxygen. Rust won't form rust, it's not perpetual.

[V8&4spd]

The decklid in the picture has lacquer paint on it. I brushed it on right over the top. I have left some of it on other stuff without rinsing it off with water. It becomes sticky after it's on a few days without rinsing it off. I leave it on overnight when there is lacquer paint on the car. It will loosen some of the lacquer paint. The factory primer is some tuff stuff, it does not seem to do much to that.