Well Damn... Yes it will! From here:

http://www.metalwebnews.com/howto/rust/rust.html

Phosphoric Acid etch will leave a hard, bright metal finish. This is because it will etch the surface slightly, exposing new, bare metal. Often this is desirable. It leaves an attractive surface and a surface ready to paint. A common product which contains Phosphoric Acid is Naval Jelly. The soft drink Coca-Cola contains Phosphoric Acid, so Coke will etch rust. But Coke also contains carbonic acid and other nasty things. You're going to drink that stuff?

Auto body shops treat metal with acid metal wash, a solution of Phosphoric Acid and alcohol before painting. This removes waxes and oils, removes slight amounts of rust that form between sand blasting and painting, and leaves a thin protective coat of iron phosphate. One commercial solution for this is DuPont Quick-Prep. Sherwin Williams has a similar product called Metal Prep.

 

Id like to know what you think of metal ready and the results. I was thinking of using this product this spring when i begin the work on my own rustang

 

I have a lot of surface rust on the bottom of the car, would this be a good idea to clean that up, then just put some kind of sealer on? I live on the Gulf Coast, and if the humidity drops below 90% we think something's wrong when we can't feel the air around us, so rust is a big issue.

 

These work great for surface rust. Rust that is not set deep into the metal. If you have rust under the car or into the frame that is very severe, the correct thing to do is cut it out and replace it. A lot of people can't do that for a variety of reasons, so there are some that have come up with ingenious solutions. I would only use these as temporary fixes until the metal can be replaced.
You would want to use a Rust Chelant. They contain NO acids and completely remove rust. I just saw an article on Evapo-rust of a guy who used it to remove the rust from his frame. Pretty amazing. But you have to keep the rusted area wet or dipped in the products.. they get around this by setting up tarps to catch the liquid, using a circulating pump and hose to keep the fluid moving over the rusted area.
After all the rust is removed, use a product like POR15 to coat and prevent rust from EVER coming back. (It's a rust converter with a super hard paint that blocks air from getting in)

Here are the links to two of these products Evapo-Rust and D-Rust-It (this one has a large quantity at a good price). They both have articles on how people removed rust from their frames and tons of before and after pictures. I'm sure there are others, but these are the two I know of. I have used evapo-rust and it is absolutely amazing!

http://www.d-rust-it.com/
http://www.evapo-rust.com/

be sure to check out this article on Rust, it will tell you all your options for treating and removing rust:

http://www.metalwebnews.com/howto/rust/rust.html

Hope that helps some.

 

Not sure if the purpose of the zinc is the same here, but zinc is used to galvanize steel. There also are zinc rich paints. Zinc prevents rust from forming on the steel by sacrificing itself, if necessary. Of the two type of zinc galvanizing (hot and cold) hot actually makes the zinc a part of the steel structure (not just a coating) and it becomes virtually indestructible. Cold galvanzing is more common on parts of our cars and is recognizable by the pattern it forms on the metal. Heavy steel, such as communications towers are usually hot dip galvanzed. Light gauge steel can't really be hot dip galvanzed because the extreme temperature (840 degrees I think) warps the metal.
Not that you are going to galvanize your car...so all this info is probably pretty worthless.

 

HGC.. great explanation and far from useless.

64.5stanger.. The POR-15 products (metal ready) and great. I used the POR and their prep products on our car and will use it on the next again.

As for Coke being used.. not! The amount of PA it contains is of course low compared to these automotive products and would take way to long to etch.

 

That's the theory behind it.. Supposed to leave a protective zinc topcoat for the primer, fills in minor pitting. Much thicker that the Iron Phosphate coating that Phosphoric acid alone leaves behind. That is what made my decision to switch to the Phosphoric/Zinc product (POR15 Metal Ready) since I am a fan of PA already... maybe fill the pitting with a little more protection (Zinc) before the epoxy primer.

 

hey guys thanx for the info. Im planning to cut all the rot out and replace, however the hood/roof/deck lid only have surface rust. Should i strip or sand,I want to stay away from blasting as i dont want any media in my paint. I helped restore a 64 1/2 in Highschool bodyshop but it was in very good condition from the getgo. Im not so lucky. thankx again everyone

 

My zinc galvanizing education comes from 13 years with a large company which manufactured all sorts of stuff...from communications towers to parts of the starship Enterprise (for you trekkies it was NCC1701-D), which incidentally, had a lot of zinc galvanized parts.

 

Another good product along these lines is OSPHO. I used it where there is more serious rust conditions that I do not plan on cutting out. Here, I wire brush the surface to remove any loose rust, then take a spray bottle and soak the area with ospho, keeping it wet for 15-20 minutes. overnight, it dries, and the phosphoric acid turns the iron oxide (rust) into iron phosphate. This is inert and can be coated over.