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timstar924 · Joined: 04 Jul 2004 Posts: 284

i want to remove the paint from my roof soon to fix the rust and repaint it and i'm not sure how to go about this. I am thinking of buying a power sander but i don't know what kind, like a belt sander, regular electric sander, or rotary sander. i don't really know the difference. i want to get a cheap electric sander cus i won't be using it again probably. Anyways a lot of people told me that if i don't know what i'm doing i can easly but gashes in the metal that will require filling and worse the heat from the sander can cause the metal to warp. How can i avoid doing this. i'm thinkig of using a plain hand sander but that would take a damn long time to take off the paint and smooth out the metal.

thanks

jpab924 · Posted: Thu Jul 15, 2004 12:37 am Post subject:

warpage from overheating the meatal by using a tool you are not proficient with, yes it will happen....use aircraft paint stripper (will make quick work of the paint), and use a grinder to clean up the rusted areas.

timstar924 · Joined: 04 Jul 2004 Posts: 284

are there any precautions i can take or do to not warp the metal? like if i don't keep the sander in one position for a long time can i still cause warpage. i've heard bad stuff about chemical paint removers. how will i use it on the roof and not get it on other parts of the car? also when removing the stripper by washing it off how do you not get it other parts? they have paint stripper in a spray can in canadian tire. after removing the paint this way can i use a hand block sander to do the rest of the work or will it take too long?

thanks

Smoothie · Posted: Thu Jul 15, 2004 5:24 am Post subject:

Use chemical stripper on metal surfaces. I'd use the brush-on stuff from a can instead of spraying. Water pretty much neutralizes it as you wash it off. Generally use a scotch-brite pad to finish cleaning metal after chem stripping. Don't use chemical stripper on the sunroof if you have one - they're made of fiberglass and stripper will eat them. Trouble with sanding (in addition to the warpage) is the sandpaper will quickly get clogged with paint. You may have heard of "wet sanding" - for that an air-powered sander is used along with water for finish sanding and the water helps keep the sandpaper from clogging, but that's for sanding paint between coats - I've never heard of wet sanding with coarse paper for paint removal. I'd use chem stripper, scrapers and scotch brite pads on the metal surfaces and just sanding on the fiberglass. Wear goggles, stripper-proof rubber gloves and a respirator while chem stripping; goggles and respirator for sanding.
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"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

timstar924 · Joined: 04 Jul 2004 Posts: 284

so i have to take off my sunroof when using the stripper so after taking off the paint how do i wash the chems of with the sunroof off? Also id on't want to spend too much money, do i have to use a respirator if doing this outdoors, can i just wear those paper masks? would i have to take off my rear hatch window and winshield to remove the paint on the roof? cus its a bich to get those removedand i want to leave them in. After chem stripping can i hand sand with a block for preping for primer then paint.

Also can paint from a can look decent and not ridicolous? i guess it depends who does it. And how can i find a paint that is close to my color my color is a respray so i don't know the code and its a very dark purple purple so i don't know if i can find that in a can.

Chrenan · Joined: 15 Jan 2003 Posts: 3903 Location: Canada

I wouldn't paint your entire car with spray cans, you'll realize why after you've finished the whole car...
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1987 951 - M193 Version for Japan

timstar924 · Joined: 04 Jul 2004 Posts: 284

No... i wouldn't even think abou6t painting the whole car with spray cans i don't even want to think about how horrible it would look, i would probably cry. i just want to get the rust on the roof fixed and the roof repainted with spray can. Cus i already have a cheap spray with orange peal and chips so i will get a full pro paint sometime like next year.

Smoothie · Posted: Thu Jul 15, 2004 11:24 am Post subject:

timstar924 · Joined: 04 Jul 2004 Posts: 284

damn the chemical stripper eats lungs? that doesn't sound too safe for me too use. i can't spend like 40-50 bucks on a respirator. would doing this in fresh air outside still be dangerous without a respirator? i'm thinking now sanding down to metal will be much easier and safer for me. how hard is it to hand sand the roof down to metal with coars 40 grit paper and a hand block sander? Sounds better than dealing with those nasty chemicals and shit.

Also i think my roof will eventuall be destroyed cus on the interior side where the roof panel meets andother metal of the body and is welded together there is like cap between them than i can stick my finger in but can't see and i can feel rusty metal in ther but i can't reach it or see it to sand it or even to spray rust convertor so it will probably eventually destroy my roof. Don't know how fast. Can the roof be replaced when it gets fully rusted one day, just wondering.

And the phoshoric acid your talking about is the rust convertor right? Do you need a respirator for this stuff too?

jpab924 · Posted: Thu Jul 15, 2004 1:54 pm Post subject:

The acid smoothie is refering to is a chemical ethcer. It prepares the metal for the primer to adhere to. There are primers out there that have self etching properties. Vari-prime (sp?) is one I`ve heard of. There are some out there are even sold in aerosol cans.

You should always use a respirator when doing bodywork.

Hows the rest of the car doing? Is it running right? Does it have good tires and brakes? Worry about the things it needs to keep it on the road first. If you are tight on cash, and need to repair the roof for a water leak, keep it simple.

Make it a small area (just the affected area) that you repair. Use a grinding disk on an electric buffer, and grind out the rusted area. Fill with bondo, sand it smooth, primer it, and find a close match to your paint at the hardware store. This is by no means the right way to do this job, but a temporary patch.

Do what you can afford to do, but make sure the vehicle can perform its basic functions.

Lizard · Posted: Thu Jul 15, 2004 2:06 pm Post subject:

you can use an electric sander and yes it may jet abit gummed up but it isnt that bad, and as long as you are working about a 1 foot section and are NOT leaving the sander in 1 spot ie CONSTANTLY moving the sander you will be fine, as soon as you cant touch the metal with your bare hand due to too much heat then turn it off and wait for it to cool down, however the way they are speaking of with chem strip is by far the best way hands down
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timstar924 · Joined: 04 Jul 2004 Posts: 284

yeah i am tight on cash and i have to fix a bunch of other stuff, like door stick ot and won't fully close, the headights unit is messed the headlight can't fully close cus it hits the body panel weird can't figure it out, i think i will need a whole new headlight unit from another car. Also i just had coolant leak.... but it doesn't look bad its jsut a old hose that is leaking should be cheap to replace. My brakes are ok now, not great but fine, brand new tires on the car, i cleaned the sunroof drain holes but water still leaks under passenger dash. Also i will need a new sunroof seal whichis expensive. Also another big think is my clutch pedal is very stiff and i have to get that fixed also which might become expensive. Lastly my transmission didn't go to 4th gear the one time i tried (only driven my car 2wice) so there is a chance my transmission is screwe but i don't know, i was going about 60 mph and the tranny didn't go into 4th it made a humming sound instead so i put it back to 3rd. Also headlight motor electricals dont' work on top of it not fitting. I also need a new muffler it has rusted to shits and has a hole in it.

Also my roof will eventually rust out cus i can't get to all the rust so that sucks.

Smoothie · Posted: Thu Jul 15, 2004 2:43 pm Post subject:

Actually I was saying the phosphoric acid fumes eat lungs, but the chem stripper is probably equally nasty. I use a respirator when dealing with either one. One result of breathing phosphoric acid fumes is flu-like symptoms, so if you feel like you have the flu afterward, you'll know you should have worn a respirator.

Yes, phosphoric acid is also used as a rust converter, but on clean bare metal it etches the surface to give the primer a better grip.
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

timstar924 · Joined: 04 Jul 2004 Posts: 284

Does it matter what kind of electric sander i use? i want to get one as cheap as possible to do the job. There is a mastercraft 1.8 amp sander for 34 bucks in canadian tire. its just the vibrating type sander not a belt sander or the circular spinning sander. so this can be used if i continously move it around to not overheat the metal. i'm just to scared to cause warpage cus i'll be screwed. The metal on the roof is pretty thin too. so as long as you don't continually sand and wait every for it to cool down when it gets to hot its fine?

timstar924 · Joined: 04 Jul 2004 Posts: 284

shit i actually have flu like symptoms with a sore throat from spraying the phosporic acid. is that bad?