When to use Rust Converter or to Spot Weld? 1979 Alfa Romeo

More of an art than a science - discuss metalworking and welding here.

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PostPosted: Wed Oct 12, 2022 9:14 pm

Complete newbie here and I am just now embarking on a massive rust removal and restoration of a 1979 Alfa Romeo Spider. I could use some advice from those of you with either professional or personal experience.

I am debating the most effective and efficient method in which to repair and replace the rusted corrosion on the cars body. For the severe **** (see details below) I intend to cut out the rust and use pieces of sheet metal and buy a spot weld MIG tool (for under $300).
For less severe or awkward curve areas where I know I am going to have trouble smoothing the metal, I was thinking of using the steel mesh that you use to fill the hole and then fill that with a metal epoxy. Suggestions or recommendations?

For the remainder of the rust issues, I was wondering how effective a rust converter would be? Is it just like a bondo that converts and stops rust? How easy or hard is it to sand and blend with the rest of the body? Is the black difficult to primer over? I don't intend to do a half **** job, but the fact is, I am a total novice, I don't know **** from shinola, so things like what kind of tools are best for each level of rust problem(s) I may encounter would really go a long way to helping me out!

It seems like the rust converter would be the most obvious given my lack of experience, but this poor Alfa deserves more respect than some slap and dash job. I realize I have a learning curve, but I don't want to start out taking short cuts on the car just because I don't have experience **** up enough times to know what NOT to do. I want to put my best foot forward, irrespective of my ignorance and incompetence, which I anticipate will invariably result in minor flaws on the finished product, but nothing more.

Like, if I am going to weld, then I want to get the right **** tool (or a reasonable one) and do it right. None of this bondo **** right out of the gate.

The Project - Car sat out exposed to the rain and fog for 15 years. The frame seems to have suffered the worst of it: There are two holes under the drivers side front panel about 5 to 6 inches each. Both front and back bumper areas have corroded about 1 inch completely off the underside of the frame. Each door panel has rust corrosion of at least an inch coming from the bottom up. There are also patches and spots on the doors interior and exterior and corrosion (though not severe) of about 1/2 inch where the windows are. Severe corrosion on hood (may buy a whole new one, depending on cost) all corrosion is near front of hood and near bumper.

The good news: No rust on pinch-bolts. The top is still usable and the frame is solid. Engine turns and has good compression. I live in California and have a garage. Car still looks great.

Thank you for time and recommendations!


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PostPosted: Sat Oct 15, 2022 6:57 pm
Please post some pictures of the areas you are describing. It is real difficult to offer advice without seeing the areas.
In order to do the job correctly, you will want to remove the rust, wherever you can.
Rust converters are basically phosphoric acid based products, that when applied will convert the rust, turning it black. They have to be properly neutralized in order to be painted over.
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PostPosted: Sun Oct 16, 2022 8:27 am
If you are really concerned about not doing a half assed job, then you will need to learn how to weld. Period. You will also need to learn how to do basic metal shaping. No mesh, no filler over anything but good, clean fully welded metal. You have a lot of research and practice ahead of you. This site is great for basic prep and paint, but there are other sites for doing metal patch panel fabrication (I assume there aren't patch panels available for your Alfa).

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PostPosted: Mon Oct 17, 2022 4:29 pm
Hello and thanks for the reply-

Will send pics shortly. And thank you for the heads up on the welding. This is the conclusion I have come to, so I guess now question is what the best tool to start with. And scheduling. This is going to require serious effort, and I guess that means calendaring my spare time..

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PostPosted: Thu Oct 20, 2022 5:36 pm
As far as welding goes on Sheet metal my Preference first is Gas welding followed by Tig welding and then Mig welding is Last. Mig weld bead is rock hard and almost impossible to planish out the bead. BUT Mig still has its place! I use all three methods just depends on what I am repairing. Yes welders are expensive yes Tig welding is challenging to learn BUT IF you learn to Gas weld switching to Tig is EASY!!!!! Tig welders are cheaper than Mig welders these days if you need suggestions I can help. But learn how to gas weld first! Its even cheaper!

A good substitute for welding is Panel bonding adhesives, I like them! and do use them!!! They are great because you have no heat affected zone to straiten unlike gas welding, draw back is set up most repairs will require a doubler or fish plate to get a good strait repair. Taking two to three times longer to get set up and make a nice repair is not unusual just part of the game.

As far as Phosphoric acids go Yes I use them, I dont use it strait though I use the Cold Galvanizing products from Dupont now Axalta and PPG has one as well.
As I said they are a Cold Galvanizing system and not really a Rust remover or converter although they do it!!!!!!
Your best off Blasting at lower pressures with a Mild Glass media such as Glass blast 80 grit then treating AFTER welding with a Cold Galvanizing compound in my opinion.

Also when welding coatings or metal treated with coatings such as the one I am Talking about "Cold Galvanizing" The metal doesnt like to be welded on once treated.
It can be done but not without sanding the heck out of it to clean it off, so just blast your metal clean then do your welding then Paint or treat your metal afterward. Thats how I do it.

I have one of Harbor frights big pressure pots I use for blasting.
Any metal that has Pitting needs to be blasted first!
(Beware The HF pressure pot is a cheap POS and will require repairs and mods daily to keep it working)
Some day I will find a decent Pressure pot blaster used but I am not buying one new for $1500+

Like was already said by the others Post up pics of your project!! & Welcome to forum!!!! Getcha a cold one start reading most of us started just like you.
We are all Paint and body work Whores and LOVE body work Porn please post Pics!!!!


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