Finally I am getting around to restoration on my gtb. First order of business is to repair the widespread corrosion in the rear. This is what I found when I took it apart: The last time this car was painted someone "repaired" the rust with a bunch of bondo and fiberglass. The worst areas are the lower areas of the rear fenders and luggage compartment floor. Most of the damage seems to have been caused by moisture trapped by the insulation and carpeting in these areas. I plan on mig welding in panels to replace the compartment floor, and trying something new to me for the outer sheet metal which is mig brazing. Has anyone here tried mig brazing for rust repair? It is suppose to be great for non structural panel replacement as it runs about 500 degrees cooler than welding. I picked up the bronze mig wire but haven't yet got a tank of pure argon to practice with yet. Progress will be posted and advice or suggestions will be greatly appreciated! Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
Damn!! Was your trunk used as an ice chest?!! A road-salt receptacle? Good luck - very cool that you're trying to do it yourself AND learn some new tricks while you're at it.
Another hero is born, please keep us posted on your project. Will it be a full-blown project? Sorry, I can't help much on the welding info & I've only done argon on aluminium but you can try this http://en.wikipedia.org/wiki/Mig_welding
Thanks! Encouragement from LA, Singapore, Italy and UK-where else but Fchat could you get that! I am not doing a total restoration like Paul Newmans, just decent driver quality paint that will last. This car came from the northeast and must have been subjected to the elements on a regular basis. It has had sheet metal replaced in the lower portions of the doors ar some point which will have to be redone because they weren't painted on the inside and are rusty. Also I removed the windshield (did not break ) and there are rust perforations in that area.
A lot of the early 308s didn't have paint on the inside of the doors, so don't assume that it was replaced panels, may have been Ferrari's fault. re: MIG Brazing I've got the wire & Argon, but haven't used it. One nice thing about the 308 body panels is that they're fairly heavy gauge old fashioned mild steel. They don't tend to warp when heated the way the thin high strength steel body panels used on most cars built since the early '80s. The 308 panels are a real pleasure to work on with body tools. They respond very nicely & predictably. BTW, here's a tip: Get your repair metal from a commercial airconditioning shop instead of a auto body supply shop. The commercial A/C shops stock 20 Gauge galvanized mild steel panels in sizes up to 4' x 8'. It's also mild steel & works easily. The galvanizing provides significantly better protection than the thin electro-galvanizing on std body repair panels. Got this tip from a show car building/classic car restoration shop years ago.
Be sure to emphasize to our readers that anywhere there is galvanizing near the area to be welded, should be removed (grounded, or buffed off to bare metal) as the fumes produced when the galvanizing melts is very toxic... You get what's called the "zinc chills", where you start to shake uncontrollably (it attacks your nervous system). I got that once when I first started welding years ago. Drinking milk helps to get rid of the symptoms, but the damage is already done at that point. Just thought I should point that out. As for MIG brazing, I don't understand. TIG brazing yes, but MIG, no. "Metal, Inert Gas" refers to the use of the filler metal as the electrode and is therefore consumed in the welding process. Kind-of like stick welding, but instead of the flux from the stick, you use a gas for the weld area shielding. "Tungsten, Inert Gas" refers to the use of a non-consumed, tungsten electrode to provide the heat source, to melt a hand (or even sometimes in production processes, machine)-fed filler metal. For brazing, the "TIG" torch can be run at lower temps for brazing, just like an oxy-acetylene torch.
Technically 'Brazing' is the use of a lower melting point metal (typically a Cu alloy) to join two pieces of metal. 'MIG Brazing' uses a bronze wire instead of a steel wire as the filler metal. The bronze wire has a fairly low melting point, hence you can a much lower current setting than steel wire, and heat the metal being joined less. Good point about grinding back the zinc on a galvanized pane. Was taking that as common knowledge which I know better than to do on a general forum like this.
I am sure I read somewhere that bodyshops now epoxy/glue repair panels on. Does any one have a view on this? Regards Nick
Correct, its been used for almost 10 years here at our dealership. Im not a fan of it, seen it used to bond a repair panel onto a door and it failed. Maybe a roof pan or a full quarter replacement on something other than a ferrari or a high end car.
So is you recomendation is weld or braise? I only ask because I have a funny feeling that this time next year I might need a rear wheel arch repair panel or two! Cheers Nick
The panel adhesives seem to be getting better and easier to use. Eastwoods just started carrying them, and they're pretty good about making sure their products perform well. As with any adhesive, surface preparation is critical to ensure good bonding. However, An adhesive is like any other plastic, it'll age. If you want the repair to last 10-20 years or more, I wouldn't use an adhesive at this point in time. This may be overly cautious as I know that the aircraft mfgs are starting to make extensive use of structural adhesives, and jetliners have expected airframe lifetimes of 30 years or more.
I would use a mig welder and use a wet rag to cool and help keep the metal straight. when welding a long line, spot weld and tack it in every 1.5 inches or so and then go back and keep tacking until it is welded solid. The glues will not work well on rusty panels. I would sandblast as much as possible and use por 15. If you were closer I would give you a hand.
Agreed! I use it on the inside of panels where repairs are made (not on a Ferrari) and no rust has come through.
POR15 is a paint that completely blocks both oxygen & moisture. You mecnanically (wire brush, media blast, whatever), degrease the surface, use a phosphate conversion etch to 'kill' any remaining rust, then paint on 2-3 coats of the POR15 coating to completely seal it. You can then prime & paint over the POR15 if necessary. Kits are available that have the surface cleaner, 'Metal Ready' phosphate conversion etch, & POR15 coating. It's really great stuff. Well known in the classic car restoration crowd. I used it a 3 years ago on my 308 when removing some rust bubbles that had lifted the paint, but had only a couple of pinholes thru the panel. I treated both sides of the panel, then refinished the outside using standard techniques. So far no sign of recurrance. Most auto body supply shops have started carrying it. See: www.por15.com
Critical point there. This is a product that works best when it completely encapsolates the once rust infected area. Finishing the BACK side of a repair that has rusted through is essential. I repaired an MGB not too long ago where the lower edges of the doors were starting to show pin-holes of rust. The correct procedure was of course to cut away the bad metal and weld in new metal. This car didn't warrant that degree of attention. I ground/wire brushed/sanded the exposed outer and lower surfaces then from the inside of the door I wire brushed away as much rust as possible. I then vacuumed everything clean, flushed the phosphate prep inside and out and once dry, applied POR15 to the inside of the door to the point where every surface of the inner lower door was coated and the seams were saturated. I then repeated the process on the outside surfaces. From there, it was just a case of a little bodyfiller and sanding and the repair was ready for paint. One point to keep in mind: POR15 when cured is VERY HARD. If you're going to be sanding afterwards, be careful with the application. Fill with level with filler rather than sanding this pseudo-stone! I really feel that the key is to seal or encapsolate the rusted area completely in the POR15 product THEN finish as usual.
Thanks, I wasn't aware of that and have not seen these spools of "brazing wire" at our local welding suppliers. Any special gases used with this process and/or the use of a paste flux for the weld area?
You have to use Argon to shield & cool the wire. I had to have my local welding supplier order the silicon bronze wire. They hadn't heard of it & had to look it up. Think they were just being polite, as they looked a bit surprised when they found it. Anyway, I go a 1-lb spool for around $35. Probably more now that copper's jumped from $0.50/lb to almost $3/lb.
Haven't got around to getting the pure argon cylinder yet but for those interested here's some info:http://www.cadvision.com/blanchas/54pontiac/mig-brazing.html BTW the welding supply in the link just sold me a couple of roll of the wire for about $20 each plus shipping(they were 2 lb rolls) Just a little progress has been made on my project. The boxes that covered the sides of the frame were removed and new ones were made. Being very inexperienced with metalwork, I tried to measure and transfer the measurements directly onto the metal then cut and brake/bend them. What I had after a few hours was a small pile of ones that didn't fit. Probably one of the basics to you guys that know, I realized that you need to make a template out of cardboard. This helped a lot. Also I was cutting them out with a pair of dull shears, then remembered I had bought an relatively cheapo plasma cutter several years ago but had been too lazy to set it up. What a difference! Clamp a straight edge to the metal to guide the torch and you slice through the metal as easy as cutting paper with a razor! The boxes I made are not exactly like the original in detail but will do an effective job in sealing that area. I also decided to pop rivet them in place so that the metal surfaces can be coated with por 15 inside and out. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
Phosphoric acid turns iron oxide(rust) to iron phosphate(black). You must wash off the treated area, because of acid residue. Purchasing the chemical, phosphoric acid from a chemical supply house is less expensive than buying a commercial product of "Rust Begone",etc. Use plenty of ventilation, the fumes are dangerous, acid mist. Good luck Charles
