Restoration in Steps: Rust and Best Practices [Archive] - SaabCentral Forums

: Restoration in Steps: Rust and Best Practices


SvenskBil
22nd March 2010, 01:15 PM
Hi all,

So, I've decided to put my 1986 900 SPG in better shape by steps. The first step will be rebuilding the rear suspension and taking care of rust issues on the back half of the underside. After this first step, I will analyse and think about my progress and the sense of the project... ;-)

What are the best practices?

- Naturally, for a hole, cutting and welding (with I assume weld-through primer) is the only way.

- For small corrosion at seams, what is the best approach. Cleaning as best as possible, sandblasting and then rust converter?

Actually, this car has very little rust. One small hole in the trunk and that's about it. But, some rust in the seams. Just a tiny bit. Personally I'm terrified of rust and have battled in on all my used SAABs... When I bought this car 16 years ago, I went along the underside with a Dremel tool, used rust converter and then painted. Very time consuming, but it's held up really well...

JP

pegasus50
22nd March 2010, 07:14 PM
[..] Personally I'm terrified of rust and have battled in on all my used SAABs... When I bought this car 16 years ago, I went along the underside with a Dremel tool, used rust converter and then painted. Very time consuming, but it's held up really well...JP

I'm seriously impressed with dedication you've shown your car(s) especially since you've shown that it's a solid investment, at least for collectors. :D

Hope this thread gets warm. I'm considering a modest underside rebuild and have a minor amount of rust damage to deal with. A Best Practices discussion could be interesting. I'm also curious about which products you used 16 years ago; and more importantly...do they still sell it? :p

SvenskBil
23rd March 2010, 02:34 AM
Thanks for the vote of seriousness!

I got the car at 50'000 miles. I immediately took care of the small rust spots in the seams and had to have one rear quarter replaced because of an accident. Now I've got 190'000 on the odometer. But, my car hasn't really been an "everyday driver" because I've often been in situations where the only real option was public transport on a daily basis.

I don't remember which rust converter I used back then. But, I cleaned the metal to the point where I couldn't see any rust. What always bothered me in the back of my mind was that I could not get all the rust out of the seams, i.e. the joints where two metal panels come together. There are, of course, always little "burrs" of rust that you grind into the metal, while removing the rust. You don't see them, but they are there.

After the cleaning, I used the rust converter. Then, I used rust-oleum rusty metal primer and black matt paint. The black matt paint wore off on the areas around the door frame etc. This paint is not durable, but the primer has held up... I heard by the way that the fishhook oil in rust-oleum is completely unsuitable for automotive applications. Don't know why though.

I got my first experience fighting rust on my (Belgian) 1977 99EMS and then on my 1980 900 T. All the cars from the Belgian plant just rusted away like Japanese cars of that era... The 99 EMS actually broke in two when I drove over a grade railroad crossing once... :-O

JP

pegasus50
29th March 2010, 02:03 AM
[...]After the cleaning, I used the rust converter. Then, I used rust-oleum rusty metal primer and black matt paint. The black matt paint wore off on the areas around the door frame etc. This paint is not durable, but the primer has held up... I heard by the way that the fishhook oil in rust-oleum is completely unsuitable for automotive applications. Don't know why though.

I got my first experience fighting rust on my (Belgian) 1977 99EMS and then on my 1980 900 T. All the cars from the Belgian plant just rusted away like Japanese cars of that era... The 99 EMS actually broke in two when I drove over a grade railroad crossing once... :-O JP

Rustoleums FAQ says that the reason for this is that when you take away the rust the oil has nothing to bond to and just sits on top of the bare metal. For smaller areas I think I would use leaded solder and a wooden wax coated paddle to get it into the seams then prime and paint. I've read this is popular with classic car collectors.

I'm looking for simple,fast and affordable techniques though; something that a guy could do himself in a small garage and not involve an air compressor. :roll: POR-15 is a Rust Convertor product that has grown in popularity over the last several years and has been discussed in some detail. It's affordable, but I'm uncertain if I can use it in tight applications-- like behind an inaccessible door panel. Maybe I should restrict myself to surface rust treatment only.

I gotta great laugh from imagining your car breaking apart from a completely rusted frame. Sounds like something from an old (silent) movie. You wouldn't happen to have any pictures of that? :o

saabismi
20th April 2010, 05:38 AM
I got my first experience fighting rust on my (Belgian) 1977 99EMS and then on my 1980 900 T. All the cars from the Belgian plant just rusted away like Japanese cars of that era... The 99 EMS actually broke in two when I drove over a grade railroad crossing once... :-O

JP
OT: That reminded me when we were taking our rather large neighbour to the hospital, as soon as she sat in the car, the rear doors wouldnt close anymore since the body was too bent.
I hate rust.

SOAB
20th April 2010, 04:57 PM
Im also quite interested in this! I just pulled my engine and would really like to de-rust and re-finish the engine bay before putting the engine back in! Don't mean to thread jack but this seems like it could become a real good thread to have in my subscribed threads :P

c900
14th May 2010, 03:43 AM
One thing I have learnt (the hard way) is that rusting under a layer of paint always goes further than you think it does. When I repaired a LOT of rust on the 82 900 turbo sedan I had a few years ago (silver one) the rusting came back with a vengence in some areas because it was impossible to get at all the rust without cutting away big chunks of metal in areas where welds meant it's hard to renew without professional attention.

Something I haven't quite resolved regarding rust converter is whether the rust converter should be removed after it's done it's job before repainting, or left in place and painted over. Up to now I've always painted it over.

Craig.

milos
25th May 2010, 04:36 PM
As i have found out the phosphoric acid based rust converters are the best (least aggressive to metal), acid convert the rust into ferric phosphate which can be scrubbed or left in place.... so, it is your choice, I would (and I did) always scrub it though, bare metal sounds more solid than iron phosphate to me...