My car was delivered yellow in 1969 then at some time it was painted green. The PO removed all the paint from all exterior surfaces with paint remover. (I know this because I find some hard goop in behind the doors) but not from the trunks and engine and then painted it metallic brown some time in the late 70s. I have been removing all the paint with 3M pads with air die grinder and 60 grit-sanding disks. I have removed all paint from the doors Front and rear trunk lid and engine lid and then put the engine lid in my bead blaster to remove all the color from the inside so I can do a perfect color change. When I remove the paint I find small areas where the paint seems like it had water in it or something and that caused bubbles in the paint. This car sat in a garage in Southern California for the last 18 years and it is an original Southern Southern California Cal. Car.

The thing is there are these small rust like spots after I remove all the paint. There are in the arrears where the bubbles show in the brown paint. This is like weard surface rust. It is not coming from behind. I have clean panels and the backsides are clean. I cannot pick at them. They are so small.

I do not want this to creep out from under the new paint job.

What to do,

Bob

Scotty B is a pro painter and must have an idea how to stop this. These spots are only where the paint was removed with paint remover and repainted. This was almost 30 years ago. The body had red brown primer over the bare metal and then the metallic paint. There is none of this going on where the paint was not removed and just primed over like under the lids. I have sanded all of these of layer by layer so I know.

Bob

Don't know what Scotty would say but those look like rust pits.
I would wire (die grinder) wheel them, then make sure to totally clean the panels with pre-kleeno (wax and grease remover) then seal it with something like PPG DP-40 epoxy primer.

I think Scott uses Heckler-Spies (now part of Dupont).

a friend of mine who does high end european sports car restorations actually takes the time to fill each and every one of them holes with lead ...
he hates using body filler ... all his cars are works of art, most better than factory.


anyways, plenty of chances to go crazy with this, it all depends on what you feel comfortable with ...
Andy

I worked it and the stuff is still there. It would be better if it could be neutralized if it was surface rust. It will make lots of little spots in different areas that will need super thin filler or blocking out. I will spend the time. When I finish removing the paint the body shop next door will paint the primer on it and it will come back here for blocking out.

Bob

that's because those are actually tiny holes in the metal. a brush won't do you any good there.

try metal ready or ospho and see if it reacts with the holes. if so, it should eliminate any rust still lurking in there.
Andy

The only right way to do it is to sandblast the rust pits.
Remove the rust, dont encapsulate it with any phosphoric acid (ospho etc)

I got a handly little mini blaster that is perfect for these little things.
It holds about 1 liter of sand.

Rich

it actually chemically changes the rust into "something not so rusty" ™ ...
Andy

I put a door in my glass beading cabinet. It softened it but it is not easy to do. It is so strange when you look so close at it. It looks like small stress cracks. One think is for sure; with all of the money that I am spending on my prep work I do not want to revisit this at a later date. My car is solid, sound on the larger level. On the micro level I am not just how these patterns got there from the old paint.

Bob

Yes rust pits. You have a couple options.

1 : best bet would to glass bead/ sand blast them

2 : clean as you already have and buy a GOOD quality etching primer. Most etch primers contain a bit of phosphoric acid which is a rust "neutralizer" This DOES NOT mean you can take a rusty panel and cover it with etch primer. All it means is that any small amount of rust or a very light flash rust ( 1-2 days) will be held at bay. Follow the etch up with a good sealer, best to use the same brand paint at this step.

3 : Ospho any areas in question, neutralize as directed and apply your primer over the ospho, Ospho is basicaly a FULL strength phosphoric acid, VERY nasty stuff, VERY dangerous but it does seem to work. I typically use it with a spray wand to get into hard to reach areas like longs or any closed in panel that isn't being removed.

I do use primarily Spies Hecker for several reasons. I will soon be performing a "test" of some various etching and epoxy primers to satisfy my own curiosity as well as to provide some REAL information for you guys. I am going to use both Spies, and at the opposite end of the spectrum, I will use U-tech primers. Opposite end because of price, and U-tech allegedly has an epoxy primer that is really good. I myself have serious doubts about epoxy primer because of some questionable results I have seen. What I can say right now, is I have a Jeep hood with nothing but Spies etching primer outside for almost a year and NO rust has come up. One spot where the hood was scratched has rust and it HAS NOT spread beyond the scratch meaning the surrounding metal is still protetcted and the rust is not creeping under the primer. My 944 also has been stripped bare and coated with Spies etch and Vario selaer. Been outside coverd up for going on 2 years and no signs of damage yet. + 2 for Spies

BTW Spies etch primers are also weld through. + 3 for Spies

For me the only area Spies dealer is an almost 3hr round trip -1 for Spies.

or I would have tried it by now....

Everything everyone told you already. I am a devoted DuPont user for 35 years. Spies is DuPont Premium line. +1 for DuPont and Spies.

BTW: Careful with the blasting, sanding etc. you can easily raise the metal and cause damage you don't want.