My 73' Pontiac is a solid southern car- with no rust holes or scale underneath, but it does have several areas of surface rust on the frame, underside trunk floor and gas tank. Floor pans are perfect.

It is not a show car, but more less in "daily driver" condition. I do not want to spend a lot of time or money, but want to be sure my undercarriage is protected from rusting further. The floor pans do not have any rust at all, but parts of the trunk pan and frame have surface rust. Can I just simply paint these areas with some black rust proof paint, or will that make it worse? I really do not want to do any sandblasting or sanding on this car to stop the rust, because like I mentioned, it is not a show car, but I do not want it to rust any more. Would I be better off leaving it alone and not painting?

I never drive it in the rain and it has not been in any salt- at least not for many years. When I wash it, I always spray real good under the undercarriage and wheelwells, so it is clean under there, as far as dirt goes. Being a southern car- it is not undercoated either. Suprisingly, not even any oil or grease under it.

Any advice appreciated.

My 73' Pontiac is a solid southern car- with no rust holes or scale underneath, but it does have several areas of surface rust on the frame, underside trunk floor and gas tank. Floor pans are perfect.

It is not a show car, but more less in "daily driver" condition. I do not want to spend a lot of time or money, but want to be sure my undercarriage is protected from rusting further. The floor pans do not have any rust at all, but parts of the trunk pan and frame have surface rust. Can I just simply paint these areas with some black rust proof paint, or will that make it worse? I really do not want to do any sandblasting or sanding on this car to stop the rust, because like I mentioned, it is not a show car, but I do not want it to rust any more. Would I be better off leaving it alone and not painting?

I never drive it in the rain and it has not been in any salt- at least not for many years. When I wash it, I always spray real good under the undercarriage and wheelwells, so it is clean under there, as far as dirt goes. Being a southern car- it is not undercoated either. Suprisingly, not even any oil or grease under it.

Any advice appreciated.

Do the bottom side just as you would the top. Clean, sand, take care of ANY rust issues and paint. Sweat the details!

Spray-bomb it with Rustoleum of Krylon. Depending on the color of your car you may even be able to get fairly close to the exterior color. I've done this a few times ... I always super clean the underside first, remove any rust scale, paint the frame with semi-gloss (you can unbolt the brake/fuel lines and cover with tape), then wrap the frame with newspaper and tape, wrap the driveshaft and exhaust and spray the floor pans. Be sure to thoroughly cover the car with plastic drop cloth or some type of cover as the the paint dust always finds a way to sneak into unprotected areas. If some overspray gets onto anything make sure to clean with rubbing compound or other products ASAP before it sets up. The longer it sits the harder it gets to remove.
You can use spray undercoating, but the look of body color paint is better in my opinion. The factory hit the floorpans with body color, but not a thorough covering.
Good luck.

If I went to trouble of removing all previous undercoating and grime I would use por-15 ... It will cost less than $100 and can be brushed on and painted over to almost any color and if done right you will never have to worry about rust again.

Check out following site http://www.por15.com/

POR 15 and like product are great ... but most effective when put over lightly rusted metal or acid etched metal. I don't think that it would provide much benefit if painted over undercarriage paint. I did use POR on my frame after cleaning it to bare metal, but I didn't use it on the floor pans for the above reasons.

[QUOTE]Originally posted by mddog:
If I went to trouble of removing all previous undercoating and grime I would use por-15 ...

I asked about this last night on the full size boards... I should have looked here first. My question is, after degreasing the frame, it is shiny like new steel... nevertheless it shows some staining. I bought the POR15 also, but what I want to know is what did the frame look like coming from the factory? Bare metal or painted?

Thanks for the replies. I guess I will have to get some goggles and a mask and start sanding the surface rust. I crawled under there today and took some photos. The floors are very solid- just the surface rust as mentioned on parts of the frame. Not bad for a 33 year old car I suppose.

Here are some photos of my undercarriage.

another

here is another

and another

yet another

Here is one of the rear suspension area- you can see the surface rust I want to eliminate.

one more of the front suspension area- again it is solid too, but surface rust.

last one

I've been using a product called Eastwoods Rust Encapsulator that works great on lightly rusted metal, no rust creep or bubbling on things that were done 3 years ago, its a primer that can be top coated and comes in black, red, or silver

Is Eastwood's rust encapsulator still a good product to use as a primer if you are going to get under there and grind/wirebrush all the rust off down to (mostly) bare metal, then paint with Eastwood chassis black?

I used Eastwood Rust encapsulator and under hood black...came out factory.

If you can afford to powder coat the frame it is the best way, usually about 600 bucks. If not, judging by the pics, I would use a 4 1/2" angle grinder, Ryobi 40 bucks, Home Depot,also from Home Depot in the tool section, a wire brush cup by Dewalt, about 14 bucks. Make sure you get one for a 4 1/2" grinder as they also come in 4" and won't screw on. They sell two kinds the thick wire and the fine, use the fine, one should be enough for the car as they do fade and be aware the little metal wires do fly so wear eye protection and a dust mask. This works very well.I can't stress enough how you can make a part look new by this method.Also works great for small parts with just as good results as sandblasting if you get a feel for it.
When done clean off with laquer thinner, prime with por 15, then paint with por 15. You have to prime first, this is where many people go wrong and tell me por 15 failed and flaked in 3 to 6 months. priming can never hurt and helps to add a strong foundation for paint. Anthony

I would also advise wearing goggles not just regular safety glasses if you are going to be using a 4 1/2" grinder with a wire wheel under the car. I went to the doctor twice to have metal removed from my eye while doing this, it's not fun.