This demo banner- -
Rusty bolts are a challenge, no matter what way you look at it. They're a pain to turn, much less completely remove or replace. Unfortunately, rust is many times unavoidable when dealing with outdated componentry.
But by using the right tools and having a little bit of patience, loosening bolts doesn't have to be too much to tackle.
Why rust is so tough
First, let's take a look at what makes working with rusty bolts so difficult. Rust is a chemical reaction between the iron in the metal and the oxygen in the air or water. As rust forms, it builds up in the threading of the bolt. Over time, it forms a seal, as rust from the different metal surfaces fuses together.
"Over time, rust forms a seal."
The goal when removing a rusted-on bolt is to break that bond without damaging the bolt or the item it's attached to.
Confirm the problem
Though a bolt appears rusted on the outside, it might not necessarily be the problem keeping the bolt tightly held down. Sometimes a locking compound has been applied to prevent the bolt from loosening prematurely, Popular Mechanics pointed out. This compound can be weakened using a heat gun.
Remove as much rust as possible
Once you determine the problem is, in fact, too much rust, the first step is to brush away as much rust as possible. The more rust you remove from the exterior, the easier it'll be to get to the heart of the problem: the rust that has formed in the grooves of the threading or under the bolt itself. A steel-bristled brush or similar tool will be effective in removing the oxidation.
Heat up the bolt with your heat gun
Once you've spruced up the outside of the bolt, it's time to address the hard-to-reach rust. This can be done indirectly by using heat. Metal reacts to environmental conditions, expanding when warm and contracting when cool. Because of this behavior, heating up the metal bolt is effective in breaking the rusty bond keeping it stationary. Use gloves to protect your hands and have a fireproof welder's blanket ready to protect your car from the heat.
Using a heat gun, it should only take about a minute to get results, according to the San Francisco Chronicle. Once the rust bond has broken, or at least weakened, you can begin loosening up the bolt.