If you look around in the market you'll find many chemicals that you can use. I recommend a few. They are easy to find and they work well.
The first one is Naval Jelly by Loctite. It's reliable and very easy to use. My father has been using this stuff for over 25 years.
The second is a home made mixture that you can make yourself. Ready?
Vinegar water. Just mix about a cup of vinegar to about a half gallon of purified water. That's it. You can keep it in a bottle and it will last for about a year or so.
The third chemical is called POR-15. http://www.por15.com/ Be sure to use the Pro 15 marine clean first and follow the manufactures instructions. Easy to use but a bit more on the money side.
Another popular way of removing rust without chemicals is by sand blasting. You can purchase sandblasting media from eastwood or even a place like Lowes or Home Depot. If you plan to sandblast yourself be sure to wear safety goggles and gloves as the media will ricochet off the metal. chemicals for rust repair, and how to fix rust
After a rusted area had been cleaned and chemically treated with your choice of inhibitor to kill the rust, the next step depends on what part of the car you're working on. Next would be to patch and or fill the area and body worked smooth.
If you can get to the back side of the rusted area it is wise to spray an undercoating to seal the back from moisture. Most kinds of rubberized undercoating works well. I use the Bondo brand, Rustoleum, or 3M.
This will ensure that ou get the longest lasting repair on your project. Always treat the back if you can get to it. If you don't, it's literally a open invitation for the rust to come back sooner than later.
Another trick that my father started to do about 10 years ago is stopped using galvanized steel to weld in as patches and started to use stainless steel. When welding in galvanized steel you need to make sure to grind of the galvanized area on both sites of the metal before spot welding the patch in. If you didn't do that, you'll end up with a lot of popping durung your welds.
By using stainless steel, you only have to grind a little to ensure your spot weld tips sont slip while welding. To give it a rough surface to grip. Don't worry if you seem a little lost in this explanation, we cover all of this in great detail within the VIP Training section of this site and you can learn more about that here: http://www.learnautobodyandpaint.com/vip and show you exactly how you can repair rust on your project in step-by-step detail. chemicals for rust repair, and how to fix rust
In conclusion, when using stainless, it's not only easier and faster. It's stainless so it will NOT rust! It's a great idea and we only use this steel when using sheet metal for rust repair.