Two or three coats of epoxy is optimum imho. Do not apply epoxy over acid based rust treatments without properly neutralizing the acid.

Not a fan or rust encapsulator type products. You’ll never see them used by professional restoration shops.

Don

 

Not a fan or rust encapsulator type products. You’ll never see them used by professional restoration shops.

Don

I got a quote from a local shop to restore my tub. They quoted $20,000 and two years before completion. The 69 they had there in mock up was fully covered inside with black POR15. Not a restoration shop but I would say professionals.

I've used Master Series but the car has never been outdoors or completed. I will say that Master Series recommends sandblasting the surface before application. The one thing I like about this type product is it doesn't rust beyond the scratch if damaged.

I would paint or prime all surfaces before doing seam sealer.

Jeff

 

Tommy... I'm also curious about what GM originally used on the interior floor pan and sheet metal. Was it some variant of cosmoline? If you google the topic, the '70's might've been the worst for rust prevention until they switched to some sort of galvanized sheet metal. I read in a Hagarty article that cars in the 50's and earlier had sheet metal that was three times as thick as today's cars. The 60's featured so many yearly model changes which was aided by thinner sheet metal costs. While a lot of articles claim a rubberized coating is their top choice, I still think a properly applied paint is better. JMHO- Mike

 

You need to remove the rust. It would be great if you could sandblast the floor. The sand will get rid of the rust in the little pits in the metal. The next best thing would be to physically use sandpaper or wire brush the floor. If you use Rust Encapsulator, the first step in the instructions state that you need to remove the old paint and as much rust as possible. There is no getting around this dirty part of the job.

I used Eastwood rust Encapsulator inside my deck lid (trunk lid). I did not have a choice because the area that I treated was between the frame of the lid and the top sheet metal. Blasting sand or sand paper could not reach in the tight areas. I first removed the rust with Evapo-Rust and then poured the Eastwood product in the hole and sloshed it around. I have no complaints about Eastwood Rust Encapsulator. I wonder if it is similar to POR 15.

If you use an epoxy primer, read the instructions first. Different primers behave differently to treated metal. For example, PPG DPLF primer can be applied over metal that has a phosphate coating while SPI primer does not like phosphorus. Navel Jelly is phosphoric acid base product. It is commonly used as a rust remover.

If you really want to do a good job, apply seam sealer in the the joints so water cannot collect in the low areas and start new rust. Then topcoat the floor with an epoxy primer.

 

I used Rustoleum 9100 series, 2-part epoxy. It can be used over sound rust and is more geared toward industrial use. Once dry it doesn't scratch or wear. I have stuff that I painted with it 15 years ago and it is still holding up fine.

Rustoleum 9100 series

 

I used POR15 and was happy with the results. I did have the car soda blasted while on a rotisserie. POR15 gave a good finish and is very hard. Once cured I covered with dynamat on the floor door interiors and roof. Good luck!

 

Anyone can fix rust that is clearly visible, that is simple. The rust that is hidden between layers of metal is difficult to treat, and this is what I do. Initially I drown the panels in phosphoric acid, the brand doesn’t matter, the stuff is all basically the same. Let it soak a day or two, till the rust conversion is completed. Then I coat the back of the panels, as best as I can reach, with a thinned down coating of Rustolium Rusty Metal primer. The thinned primer will run down in the bottom of the panels and coat the seams. Then topcoat if you like. Or don’t. This will help in the lower, rust prone areas that you really can’t reach.

 

If you have removed all the rust, then epoxy primer would be my first choice. POR 15 as I understand it isn't meant to be top coated?
Although I'm not a big fan of sandblasting, sometimes it's the only way, it can be very aggressive and if not done properly it can even warp panels. If the rust is minor, I like soda blasting, it wont cause damage and also leaves a residue coating that buys you some extra time before the oxidization starts.
Dipping in acid gets into the seams but I wonder how these crevices can be thoroughly flushed and neutralized after. Hopefully your project doesn't need rust removal inside seams or pinch welds.