By: Steve Esposito
Recently I looked around online to see if there is anything new out there for removing rust from automobile parts. Turns out, there is not much new that is useful, and plenty of bad information.
First, one needs to understand that steel and iron oxidization is indeed a natural chemical process and the steps you must take to prevent or reverse the process are chemical in nature too. Various paints applied to clean metal prevent oxygen and moisture from combining with the iron in the steel, which is the formula for rust.
There are all manner of chemicals out there, “natural” and not so natural to chose from, and some can cause more damage than if you just let your car or tractor rust into a red pile of dust. Sulfuric acid is one. Sure, it will strip that heavy rust right off of your parts, and the parts will start rusting again immediately. Plus, the vapor will spread far and wide, promoting rust in your tool box, the rest of your vehicle, and anything else containing iron.
Vinegar seems to be getting popular, acidic acid being the
active ingredient there, but it has some of the same problems as sulfuric acid in slow motion. As soon as you get the rust removed, the parts begin rusting immediately and anywhere the vinegar ran will begin rusting too, even if it was not before. Also, a rule of thumb is if you can still smell the vinegar, it is still eating something away.
Diluted molasses is a somewhat better option, if you can immerse your parts in a vat of the stuff. However, it makes an unpleasant odor that is fine if you are the only person who can smell it, and if your neighbors smell it they might quite rightly object. I recall a shop teacher telling me about cleaning old files with molasses in a bucket and it does work for some applications like that, however it works in slow motion and all of it needs to be cleaned from the metal before protecting the metal. In the case of a file, some fogging oil or just drying it quickly and keeping it protected from moisture should do.
In my case, I had the roof of a 1972 Dodge Charger to clean up. When I worked on the car after purchasing it about seven years ago, I stripped the car to bare metal and primed most of it with a high zinc content etching primer. On the roof, I
applied a durable rust preventing paint, POR-15. POR stands for “Paint Over Rust” and the stuff really is durable. It is activated by moisture, so as soon as you paint it on it is sucking the moisture away from the metal and the side you can see is sucking moisture from the air to cure. The same thing is happening in the can too, so buy the small cans because they don’t have much of a shelf life. Almost everywhere I applied the product, the rust is still gone. Everywhere except the roof, where several car covers and tops over the years mechanically rubbed through the paint and exposed the metal.
What to do? Phosphoric acid to the rescue! Perhaps you have heard of the “Coke trick” of using fine steel wool and Coca-Cola to remove rust from a bumper? That method works because one of the flavorings in colas is phosphoric acid. The citric acid might contribute to the process too. If you have real rust, you need something stronger. Phosphoric acid is the active ingredient in naval jelly, as well as in several of the “green” varieties of rust removers and converters.
A You Tube video by caponeauto (warning, his language can be a bit salty) highlighted a de-ruster from Royal Purple, however
these days it is only available by the case from the manufacturer or through Amazon.com in smaller quantities. Lowes turned out to have several products to select from (aisle 12, at the end closest to the registers). But which to select?
Since phosphoric acid is roughly 50% heavier than water, the heaviest quart bottle should have the most of what you are looking for inside. I did not tote a scale into the store, I just selected which one felt heavier, a quart of Jasco rust converter. While it did not come with a squirt-top bottle, it was almost $2 cheaper than the stuff with a squirter, which is not the only way to apply it anyway. If you are lucky enough to work on your project indoors at a decent temperature, you can get to work as soon as you bring it home.
My project is in the driveway, so I am limited to warm enough days without rain, which have been pretty rare lately. Still, I rubbed off the surface rust with a scuff pad, dusted, then sprayed on the first application with a squirt bottle I already had laying around. After it appeared dry, I covered the car back up for a couple of days until the weather agreed with the project again. Nearly all of the rust was gone,
except for places I missed or places I should have knocked it down more through abrasion. Repeating the process another couple of times knocked it all out.
Something else to note, the folks who use sulfuric acid, vinegar, or molasses to remove the rust, typically come back with phosphoric acid to keep the rust away. I say, why bother with the other stuff when you can go straight to what works best?
The next step is applying something to protect the metal. Most rust projects do not require automotive grade paints, so if you are doing your iron railing a can of rust preventing paint is fine. In my case, I’ll be using an automotive grade “cold galvanizing” paint. Essentially, it is very fine zinc mixed with clear paint. To prevent the original problem of the cover rubbing through the paint, I will be using a pad between the roof and the tarp because doing this job twice is more than enough for me!
A video of this project will be available soon at my blog.
© Steve Esposito, 2014.
Cover Photo © Genevieve Martin, 2014.