I'm finally digging into my 82 Brat to get some of these rust issues repaired. Thought I'd tackle the worst one first. This is on the drivers side below the back of the drivers door. Looks like where the back section of the body was welded to the front section. Seems to be an overlap and a great place for rust to form. There's a similar place on the passenger side, but not quite as bad. Do I need to repair this as a structural fix or just cover it up and paint over it? There are a couple of other smaller rust through spots on the rockers, but they are mainly small and I'll probably fiberglass those.

In order to completely stop the rust, you need cut out all the metal that's rusted, even slightly, clean it and coat it with a GOOD anti-rust coating, then repair it. The rocker panels are structural, so I would not use fiberglass. You'll need to find good ones and graft them in or make new panels.

2 hours ago, Bratastick said:

Do I need to repair this as a structural fix or just cover it up and paint over it? There are a couple of other smaller rust through spots on the rockers, but they are mainly small and I'll probably fiberglass those.

 

The internal rust is the issue, not what you can see.  

1-3 year fix = cover it up. 
Permanent fix = cut it out and replace the metal. 

There's unfortunately no way to get a permanent fix otherwise.   You could possibly increase that 1-3 time line by a year or a couple with an enormous amount of effort applying POR-15 into the inner reaches of the cavities. 

6 hours ago, idosubaru said:

The internal rust is the issue, not what you can see.  

1-3 year fix = cover it up. 
Permanent fix = cut it out and replace the metal. 

There's unfortunately no way to get a permanent fix otherwise.   You could possibly increase that 1-3 time line by a year or a couple with an enormous amount of effort applying POR-15 into the inner reaches of the cavities. 

That's always the issue on a fix like this. I can prep the area inside and out with some rust remover/preventative then do a patch that does not require heat (fiberglass or some type of panel bonding) and call it good. The issue with welding a patch on is that once done there is not a way to recoat to mitigate a continuation of rust caused by heat during welding since there's no way to get back in there. It's a boxed in area.

Do you know of anyway to do that?

8 hours ago, skishop69 said:

In order to completely stop the rust, you need cut out all the metal that's rusted, even slightly, clean it and coat it with a GOOD anti-rust coating, then repair it. The rocker panels are structural, so I would not use fiberglass. You'll need to find good ones and graft them in or make new panels.

I agree, metal would be preferred as to strength, and this is in an important location. I would guess finding a good rocker panel would be near to impossible, so fabricating will be the only option. 

I've got some 16 gauge cold rolled, but it's really stiff and hard to work with. What is a good sheet steel to use?

Edited May 19, 20205 yr by Bratastick

4 hours ago, Bratastick said:

That's always the issue on a fix like this. I can prep the area inside and out with some rust remover/preventative then do a patch that does not require heat (fiberglass or some type of panel bonding) and call it good. The issue with welding a patch on is that once done there is not a way to recoat to mitigate a continuation of rust caused by heat during welding since there's no way to get back in there. It's a boxed in area.

Do you know of anyway to do that?

Nah, that’s beyond me.  Giles is a member here currently doing extensive restoration work on a rusty XT.  It’s incredible at the moment.  He’s got the front done or nearly done. Cut out, strip, fab, weld, prep, etc. welding and boxing in shouldn’t be a problem if done right.  But Rust repair “done right” isn’t something I should be guiding!

The rockers have some holes you can get at from the inside.  And you could add a few if needed to get coatings inside.   But, yes, you have to coat the inside of welded repairs.

 

How to do inside rockers -

https://www.hammerite.co.uk/product/waxoyl-pressure-sprayer/

 

There are also paints you can use to coat the inside of a boxed weldment, but I'm forgetting what it's called...

23 minutes ago, carfreak85 said:

There are also paints you can use to coat the inside of a boxed weldment, but I'm forgetting what it's called...

yes, I've been looking for some sort of siphon spray gun with a flexible hose on the end that I could connect to my air compressor. I've seen one at Eastwood and Amazon that go on a spray can, but they don't get that good of a review. 

That's what is in the link I posted.  I'm not sure what powers the new version, I have one from 20 or more years ago, that has a hand pump to pressurize it.   The professional ones connect to an air compressor. 

The thing about waxoyl is that unlike paint, it does not get totally hard, it seeps and creeps into small places, and existing rust you can't see or didn't know was there.  Also, to a point, it's self healing.

Fooled around a little more last night and found another area that was covered up by a previous repair. The front fender was replaced at some point due to an accident. Looks like they just tried to pull some of the smashed area out then covered it with bondo. Some had fallen out, it was about a 1/4 inch thick.