I just got this 91 Z28 and it runs great and the interior is good, etc. A body shop guy looked at it and it has some rust underneath. It came from Detroit and I guess the previous owner may have exaggerated a little when he said it was never driven in the winter. The Wheel wells have a littel rust, but the back bumper support and the underside of the body along the seams has rust. I was thinking of buying a metal grinder and grinding of all the rust I could, then painting the spots with rustoleum primr and just leaving it like that. No one is really going to see it under there and Im sure it would significantly slow or stop the rust. I guess it's true what the body shop guy said that it's like cancer, its almost impossible to get it all, and its just going to come back. I wanted to keep this (or another) car for a long time, 10 years or longer. If its not this one, I might just keep it and enjoy it for a few years and then get one from California or Arizona or somewhere and make that one the long term car.

What do you think about my idea for rust treatment? Will it be worth it? Can it cause any harm?

 

I'm getting ready to coat my underbody in a paint called POR15. You can see it at their website here. This paint actually converts rust into a hard metal that wont chip even with a hammer. It also stops rust from spreading. I am curious what prep is needed though.

-Matt

 

I second the notion for POR-15,dont forget to coat the battery tray before it rusts through.The previous owner of my 85SC didnt care about the car getting rust

 

I think I'm gonna use some POR-15 on my car. I don't have any underbody rust and I wanna keep it that way. How hard is it to apply?

 

It's easier than painting a model. Brush or spray, doesen't matter. I'm going to get a large brush and paint everything. Then I'm going to paint the tranny, panhard bar, rear, and a few other things red so they stick out if you're behind me, or under it for a little extra touch. I'll post some pics when I get the paint in and on.

-Matt

 

Absolutely use POR-15. It doesn't convert the rust to metal, it seals all oxygen away from the existing metal, and unlike paint (for example Rustoleum) moisture hardens the POR-15. I have used it for years on my restorations and on my construction equipment without any failures. Its the best stuff around. Just be sure to put a dust coating of primer on the POR-15 before it drys, otherwise your paint may may not stick to it.

 

Remove any loose rust and scale. The company says POR-15 actually works best if there is a light coating of surface rust left on the metal, however I haven't had any problems on parts I've sandblasted.

 

On a similar note, i'm pulling the engine in my 84, and blasting out the compartment. People have been telling me to epoxy prime it all to keep rust out.

I know nothing about it epoxy primer. Is it better, the same, or worse then POR-15, and is it pricier???

 

I went ahead and ordered this stuff, it looks great, much better than what I was thinking of doing. I ordered the Chassiscoat Silver instead of the semi glossy black they recommended. I will use this for the undercarriage of the car and it looks more silver to me than black. I'll let you know how it comes out, thanks for the info. I may be able to salvage this car as my long term keeper yet.

 

A couple of tips:

When you get the POR15 punch a couple of holes in the lid of the can and pour out just what you need (after shaking it on a paint shaker, take it to a store if you don't have one) and seal the holes afterwards with duct tape. This tip is really good for cans that have gotten material in the cap groove, and can't be opened too. Store the POR15 can upside down so that air can't get in (make sure your holes don't leak). Remember that POR15 is light sensitive, so storing left overs in a glass container won't work.

If you do take the lid off, be sure to put a piece of celophane between the lid and can. POR won't stick to the celophane, and you'll be able to get the lid off next time.

Buy a few cheap brushes, and just throw them away after you are done with them. Don't bother trying to clean them.

Don't get it on your skin, it'll be there for a few days. Be really careful not to get any in your eyes, especially if you are using it overhead.

I use the silver too, and any POR15 that is exposed to direct sunlight will turn a yellowish color.

 

So as I said, I ordered the POR15, plus the marine clean, etc. The only surface preparation I was planning on was going to be going over the rusty areas with a power wire brush to remove any loose rust, scale, or metal, then going in with the cleaner. The way I understand it, it is not necessary to grind away all the rust, just loose stuff. Apparently the undercarriage is usually painted the color of the car as it was mentioned elsewhere on this website. My car is black and the undercarriage is kind of silver. This may be due to some previously applied protective coating. The POR15 will all be covered with the chasssicoat silver color so none should be exposed to sunlight. There shouldn't be much sunlit getting to the undercarriage of the car anyway unless I am driving terribly bad and end up upside down.

 

Thanks for the tips Blue502 and all others who have responded as well. I don't feel so bad about buying the car now that I think I can control the rust