Rust - methods used.

[katsi]

OK guys and gals, I now have my rust exposed, and ground down to metal. What I was wondering was (besides welding, which I don't know how to do) which is the best way to fix it. Let me go a step further and explain that it's few spotts going along the floor pans allong the outside beam. I was thinking of using (on the under side of the car) a bead of that spray foam and then covering that with some of that rubber undercoating. Then following it up on the top side with some fiber glass and a few screwed in metal patches for the larger areas. Yes? No? Any other meathods used successfully for a non welder? The cross member is strong and unrusted.

[amsiegel]

Pop riviting might be better than screwing.

Instead of spray foam you might want to try some automotive seam sealer.

[stefhahn]

I did try maaaany methods in former lifes - if you cannot weld yourself the best method that prevents further rust is taking the car to a body shop. All others will result in a mid-term (and more expensive) rust fest that typically ends in "selling for parts".
ciao,
Stefan

[wachuko]

I did try maaaany methods in former lifes - if you cannot weld yourself the best method that prevents further rust is taking the car to a body shop. All others will result in a mid-term (and more expensive) rust fest that typically ends in "selling for parts".
ciao,
Stefan

+1. I don't have a Fiat Spider... but for any car that requires metal work due to rust, the best thing to do is to cut the bad and weld a replacement panel. Anything else will be wasting your time and money... if you can't weld, get the replacement metal and take it to a shop to do the welding. Then you can continue with the sealer, primer, and paint if you are confortable with those tasks.

[NitroDemon]

If you've got surface rust thats just causing dimples in your metal and you want to effectively stop the rusting, theres this stuff called "Rust Mort" that does an amazing job of turning rusted metal back to solid metal again. Well, you'd wanna knock off all the loose stuff then spray the Rust Mort on the area and let it sit. The metal will turn black and thats when you know its done. you can sand it back to a nicer color afterwards then do your body work. Its a bit expensive, around $25 for a QT and $60 for a gallon but it works great at killing rust!

[Foster48x]

Katsi,
Like the guys said welding is probably the best route but I didn't have access to a welder either so here's what I did.

Cut out as much of the rusty pitted metal as possible.
Sand or wire wheel the rest of it (front and back) down to bare metal.
Treat all of the rusted metal with Phosphoric Acid or some type of rust converter.
Cut out and and treat your new sheet metal.
Rivet the new sheet metal in place.
Seal (front and back) the new sheet metal with Bondo Fiberglass Resin Jelly (The green stuff from just about any hardware store).
Sand down any rough edges.
Prime and paint or seal it over again with something like POR15.
I also went over that with sound deadening material.

Rick

[Foster48x]

I'm pretty sure most of the rust converters convert rust with Phosphoric Acid. Instead of paying for all of the fancy name brand stuff I just bought a gallon of Phosphoric Acid from Home Depot and dispensed it out of a spray bottle.

Rick

[wachuko]

Just one suggestion to that list. If you are riveting the new sheet metal to the old one, use some epoxy glue between the parts to avoid any condensation build up and future rust in that joint... Done right, you can even avoid using rivets. This is the stuff they use to bond the door skins to the door frames.

Katsi,
Like the guys said welding is probably the best route but I didn't have access to a welder either so here's what I did.

Cut out as much of the rusty pitted metal as possible.
Sand or wire wheel the rest of it (front and back) down to bare metal.
Treat all of the rusted metal with Phosphoric Acid or some type of rust converter.
Cut out and and treat your new sheet metal.
Rivet the new sheet metal in place.
Seal (front and back) the new sheet metal with Bondo Fiberglass Resin Jelly (The green stuff from just about any hardware store).
Sand down any rough edges.
Prime and paint or seal it over again with something like POR15.
I also went over that with sound deadening material.

Rick

[Foster48x]

wachuko, good point about using the resin between the parts. The Bondo Fiberglass Resin is also just about strong enough not to use rivets. On some of the smaller pieces I chose not to rivet them but decide to rivet the larger pieces for the added strength.

Rick

[wachuko]

wachuko, good point about using the resin between the parts. The Bondo Fiberglass Resin is also just about strong enough not to use rivets. On some of the smaller pieces I chose not to rivet them but decide to rivet the larger pieces for the added strength.

Rick

That epoxy is better than using the fiberglass resin. Is what I used on my motorcycle to glue a canard to the tank (tank extension) and also what I am using to glue the quarter panels in the RSR I am building...very little need for rivets. Once cured, the rivets are not providing the bond. They are embedded in epoxy so they will not back out over time. It was recommended by a local race shop and I have received the same recommendations from folks that are using it for other car projects. If it holds in race cars, production car doors skins, it should work just the same for this task.

No, not affiliated with the company, blah blah blah... just sold on it based on what I have see that stuff withstand.

[pooldoctorstl]

I have to agree with Stefan. If you don't have the ability to weld in new metal yourself, take it to someone who can. I have not seen the rusted through areas, but you said it is in the "outside beam". Remember that ALL of the structural integrity of our cars is in the floors and unibody structure (outside beams). By patching areas where the metal is gone with anything other than welded in metal you are loosing some of that structural strength. It will cost a bit more but it will be done right and last a lot longer.

Good luck,
Jeff

[eddy314]

I was told by a classic Jaguar restoration place that they will use the fiberglass matt and resin method to cover holes in the pan. The same as what's used on boats. It adds strength and sound deadoning. That is as long as the hole is not too big. Then either weld or pop rivet a panel, then glass over. If its all glassed over no more moisture can get to that area. Thats what I intend to do.

[htchevyii]

I agree that covering up the rusted area will just lead to more rust, but I do feel that other methods can be nearly as good or possibly better than welding for non-structural areas PROVIDED THAT ALL POSSIBLE RUST IS REMOVED. The problem that I have noticed with welding is that unless you can get to both sides of the weld to clean the weld and paint it you have a contaminated bare metal surface that is allready starting to rust. I feel that removing all possible rust, coating with Master Series and bonding new metal with body panel adhesive or fiberglass the repair will be strong and quite possibly more rust resistant than by welding, provided a good job is done and there aren't cracks or gaps for moisture to hide in. Of course it won't work in structural applications, (actually I think I read somewhere about a car with a carbon fibre and aluminum frame that was held togeather with panel adhesive, Lotus?). The repair also might not look as good as a well done welded one, but with prober attention to detail and some sanding could. Opinions are sure to differ, but there are some good products out there these days, good luck.

[Foster48x]

wachuko, good point about using the resin between the parts. The Bondo Fiberglass Resin is also just about strong enough not to use rivets. On some of the smaller pieces I chose not to rivet them but decide to rivet the larger pieces for the added strength.

Rick

That epoxy is better than using the fiberglass resin. Is what I used on my motorcycle to glue a canard to the tank (tank extension) and also what I am using to glue the quarter panels in the RSR I am building...very little need for rivets. Once cured, the rivets are not providing the bond. They are embedded in epoxy so they will not back out over time. It was recommended by a local race shop and I have received the same recommendations from folks that are using it for other car projects. If it holds in race cars, production car doors skins, it should work just the same for this task.

No, not affiliated with the company, blah blah blah... just sold on it based on what I have see that stuff withstand.

That 3M Automix is good stuff. I also have friends that swear by products like it. I guess it just depends on your budget; rivets and fiberglass resin will run you 10-15 bucks, a really good commercial grade adhesive like Automix will run you around $40 (200ml).