The Stovebolt Site Forums The Shop Area Paint and Body Shop School me a bit on rust, please...

I have been restoring and repairing cars since I was 15. I am 63 now. I am a darn good mechanic and not bad at paint and body except for one issue. My nemesis, rust!!

My very first car, bought when I was 15, was a 1954 Austin-Healey 100-4. Bought in decent running condition for maybe $350. I was going to fix it up well in advance of getting my license. My dad was supposed to help. Long short, my dad bailed and I could not get past the rust beneath the aluminum panels.

I love Alfa Romeos and have owned about 10 of them over the years. Usually, late 70's and early 80's. Google Alfa Romeo rust. They are infamous and they melt away.

So, guess what? Now I own a rusty 1972 GMC Sprint and the time has come to conquer this dragon.

Lets leave off replacing panels or welding in patch panels and let's just address dealing with rust in place, please. This is because my 1994 GMC pickup has some serious surface rust issues that I would like to fix first.

Please give me some feedback on the following methods and feel free to correct my misimpressions:

- Muriatic acid: Obvious handling and disposal hazards. [u]Removes[/u] rust quickly but may damage substrate. Flash rust from fumes.
- Evapo-rust: [u]Removes[/u] rust slowly. Safe to use.
- Phosphoric acid: Obvious handling and disposal hazards. [u]Converts[/u] rust, does not remove it.
- Ospho: Similar to phosphoric aid.
- POR-15: [u]Converts[/u] rust and acts as a primer? Best used in areas like undercarriage, not suitable for finish paint?
- Did leave anything out? Vinegar?

So if you had a body panel with significant surface rust, how would you prep it for finish paint?

Thanks

Prep for paint... scratch off the por stuff.

Muriatic avoid
Ospho is phosphoric acid and what I use... or some mix like it.
Milkstone remover (dairy farmers use it) is about twice as strong as ospho and the top end of acidic range I'd go.
If your going to paint high end or low end, epoxy primer first. But the acid must be properly neutralized and removed despite what the ospho label says...
You could use something like Rustoleum cause cheap paints don't care.

Vinegar works too about 1/2 as strong as ospho...

I like Ospho if I can't media blast down to white metal. After 24 hours, I wet down a rag with Ospho to wipe off the white residue left from the chemical reaction. I then wipe it down with acetone (you could use wax/grease remover), before epoxy primer.
Carl

I'm right with you up to the acetone. ..
Id wash it (I have pure enough water) and blow dry (shopvac) then epoxy.

And yeah this is based on no media blaster available. Thats first choice.

I'm amazed to hear anyone suggesting vinegar as a rust remover. Vinegar is what rat rodders use to RUST new metal to make it look old; spray it on and parts are quickly rusted. I also use vinegar with a steel wool pad in it to make fence stain; vinegar completely dissolves the steel wool overnight - I mean actually GONE.

They could just use the ospho... spay on wait a few minutes and wash off...
Sure new metal will flash rust but the issue isn't harmless surface/flash rust a red skuff pad will remove.
The OP is trying to deal with real rust.

Ok, I am a novice painter but I have decent results and I look for longevity of paint adhesion. My first choice is blasting and after I may stll have pitting with rust color in them or not. If exterior metal, I knock down the blasting with scothbrite. If hidden I just blow off the sand then zero rust. Metal is thin on many of the 40's trucks. I replace panels if no metal but if still solid but thin I use zero rust to seal and then use it as the first primer coat. Eastwood has a similar product. After scuffing, I then apply bondo if needed and if I sand thru to bare metal I use an etching primer before a filler primer. From my experience I can use about anything over the zero rust that has been surface prepped for primer/paint. Again I do not restore 40k plus vehicles but they do last until someone wants to put a $10k paint job on it.

I like to use Phosphoric acid with zinc salts (there are a lot of products available already mixed). This converts the rust and then leaves a zinc phosphate coating on the surface to prevent further rust. It will give you several days without worrying about flash rust. Plus, the zinc phosphate has a chemical bond with the metal and you can paint over it. It is used a lot for powder coating when you need extra corrosion resistance.

Chad

always wear gloves using acetone,, it goes right through your skin and is captured in your Liver