I have a car with rust pitted hood and roof. what is the proper way to prep for painting? should I sand it until its all bear metal with pits? I don't think I can sand far enough down to remove the pits. how do you get the rust pits out? which sanding method works best. it will take for ever to sand entire hood and roof. thanks

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1970 Chevelle 454 Wagons haul A$$ in style! "The Chopped Suburban". to see some goto www.EINSTYN.com (http://www.EINSTYN.com)

To do this properly, you HAVE to remove all of the rust. If you don't, it will come back to haunt you. Some people may reccommend a 'rust convertor'. No way would I use anything like that on such prominant body panels. DA sand the panels with 80 grit. Watch for heat build up. You could warp the panels if you concentrate on one spot and build alot of heat in the metal.
On the rust spots remaining, take a 36 grit disc and gently clean out as much rust as possible. Don't go crazy with it though.
Now play like a dentist and get your dremel tool out. Get ALL of the rust out. All of it!
Now you have a bare metal surafce that looks like the moon. That's OK as long as you didn't warp it. Now use a self etching primer. Then apply three good coats of a quality urethane primer surfacer. The block sand the surface and repeat the primering until you have a smooth surface.

This is a tough one for HOME remedy.
You must remover the rust on the substrate B-4 overcoating. Wire bush ( I like the one that encapsulated in the rubber wheel ) I never tried the rust converters on outside body panels, but might be an option.
I have used a Snap-on Vacuum bead blast. but this is in a commercial body shop. IF you have access to a pressure blaster. get a few bags of walnut shell media or plastic media
to blast rust in pitted area. BUT DO NOT use SAND it will warp the panel !!!!

Wayne

I hear Aluminum Oxide media is really good for rust.. Not sure about the pitted areas though.. But Media Blasting and the wash/stch primer than a good 2K primer would be the way too go!

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Try those 3M rollock thingies - the ones that looklike round black sponges. Use that perpendicular tothe pits to get alot of the rust out, worked good for me, even with deep pits.

When all else fails, break out the dremel - those things are lifesavers.

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1970 Chevelle Malibu (http://communities.msn.com/TeamChevelleMalibuDreamerpics/shoebox.msnw?action=ShowPhoto&PhotoID=1)
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May want to try muratic acid. I don`t know how well it works on panels(never did it) but it works great for small parts you can dip. My .02....

Jim

Normie, not to be a smart A$#, but Aluminum Oxide is still to abrasive for pressure blasting body panels. It's cool , after you remove a 1/4 or front end/ and want to clean up your rad support or cowl or wheel house. Bur IMO not for hoods, roofs or other outside body panels.

Wayne

You need to take this to a professinal media blasting shop. Plastic will not remove rust, they will use alox or similar aggressive materials that will not harm your parts. Sanding will only take off top layers of the rust, pits are still there so it does need to be blasted to remove all contaminated areas. You can go over it with a self etching primer after. I would also make sure you do both sides of the hood and not just the top.

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Micky Hale Restorations
69 L-89 Chevelle
68 Biscayne 427/425
34 Plymouth Drag Car
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Wayne no Offence taken http://www.chevelles.com/forum/smile.gif The guy that told me that was looking at some of the structure parts of my car when he said that! So I wasn't positive that it would be good for sheetmetal.. which is why I posted as Hearsay...

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I've used rust remover and also have used muratic acid wixed with water to remove rust. Just make sure you rinse the metal with lots of water, then rinse with water mixed with baking soda to neutralize the acid followed by rinsing with water again. After that, the metal will flash rust, be sure to dry it off quickly. To get rid of the flash rust, I just use metal prep and wipe down the flash rust. Ready for primer!

Media blasting is the best,but for a home job i would soak the area with Naval Jelly(a rust dissolver available at most hardware/auto parts stores.Leave it on overnight.When you come back it will be black and crusty.Take a stiff wire wheel on your drill or die grinder and clean out the pits until the metal is clean and shiny.this will remove the crusty residue along with any rust leftover and you dont have to put water on the bare metal.Clean the metal good and use a self-etch primer or use a metal wash with an epoxy primer.

Media blasting is by far the best method, a wire brush will just take to long for me anyway. Plus the wire brush wont do the job a media blaster will. Like mickey said do both sides and a wire brush on the backside would be a nightmare to do. Use a self etching primer dont apply expoy primer over bare metal a big no no.

I suggest replacing the hood.
A nice non-ss hood can be had for $50, the materials to clean your hood will cost close to that. If it's an ss hood, then consider a repro for around $250, it comes ready to paint.

[This message has been edited by 68ElCamino (edited 12-05-2001).]

thanks guys. its a cowl hood and I would like to use it. I am willing to get it as good as I can and leave it at that. if it rusts again in 5 or 10 years that's ok. I do have a sand blaster. what's wrong with the the white play sand from the hardware store? if that's not good, what media is best. I just see "media blast". I was considering paint remover on the hood followed by DA sanding down to bare metal. what specifically is the product to put on the bare metal with or with out some remaining microscopic rust pits. is it the metal etching primer? what name? on the roof however I will need to be more particular, I want it to last forever! I guess I will be dremiling out every pit! or carefully blasting. but would still need product to spray over that. thanks.

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1970 Chevelle 454 Wagons haul A$$ in style! "The Chopped Suburban". to see some goto www.EINSTYN.com (http://www.EINSTYN.com)

If you're very lucky it will take five to ten years. I got rid of some rust pits on my Elky early this year. 95% of them turned out good. But a few have already come back to haunt me and it's only been 9 months. I thought I'd got it all.

I'm gonna take 'em back down this spring, cut out the metal on the really bad spot and replace with new steel.

I had no trouble cutting out the area under my rear window and welding a new panel in place. Welding flat patches to replace rusted metal will be a breeze compared to that.

Can you believe that I actually enjoy this?!? http://www.chevelles.com/forum/biggrin.gif

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Chad Landry
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'68 El Camino

[This message has been edited by cjlandry (edited 12-07-2001).]

Fo, any type of sand blasted onto those areas be it the roof or hood will warp them so fast it will make your head spin. Sand is just to abrasive and creates to much heat to be used on sheet metal just use it around door jams or the floors not sheet metal.

The term media blasting is so confusing. Media blasting is using medias other then sand to remove paint. Like plastic, glass, walnut shells, or even baking soda. Plastic will not remover rust. On the other hand baking soda will remove the rust. Or you might want to consider going to a commercial chemical stripper, they will dip the part into a solution that will remove all the paint and rust and not weaken the part.

The da sander will only remove the top layer of rust not the low laying rust. Using a 36 grit grinder also will not remove the rust, it can if you really bear down on it but leaving the metal thinner in spots.

Use a wash primer or self etching primer NOT AN EXPOY PRIMER over the bare metal. Each company has an etching primer, PPG is dx1791, Dupont is variprime. I use the stuff from sherwin williams but cant think of the name. You paint over any rust I dont care if it is just a small speck of rust it WILL not last no 5 to 10 years more like 1 to 2 if you are lucky.

If I was you I would just spend the money now and have it media blasted by a pro. It might cost more now then what you want to spend but in the long road be the best road. Repainting a hood from stracth every two years because of rust is not something I want to do or even pay for. That repaint in two years will cost more then what it will cost at the blasters, I know what I would do in your shoes.