Rust + heat = no problem, but why?

Put this in the OT forum 'cause I just didn't know where else to ask something like this.

In my (limited) experience any connection that is rusted shut can be opened with some heat. It works so well that I reach for the torch before the socket set when I see the red stuff all over. I saved a found pair of visegrips this evening with the torch. They were rusted so hard that the wouldn't even budge and now they're in my toolbox.

My theory is that the steel expands *and* the rust actually gets burned away when things get hot enough. I know this is totally frivolous, but are there any other theories about why this works so well?

Thanks

Its magic?

your actually on the right track with the expansion of the metal but the rust does not burn off it is actually broken out of the joint by the expansion and contraction of the metals.

works the other way around as well when i work on cars and trucks and have to say remove an exhaust manifold and all the nuts are rusted to the studs i take a "canned air" keyboard dusty and turn it upside down and spray the bolts down the sudden freezing from the co2 blast then quick thawing once it evaporates breaks the rust up then when you spray it with some penetrating oil the oil can actually get to the threads and bust the rest of the rust loose (sometimes oil is not even necessary after freezing but i hate drilling out broken studs so i still do it as a precaution)

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Originally Posted by ilovejunk

your actually on the right track with the expansion of the metal but the rust does not burn off it is actually broken out of the joint by the expansion and contraction of the metals.

works the other way around as well when i work on cars and trucks and have to say remove an exhaust manifold and all the nuts are rusted to the studs i take a "canned air" keyboard dusty and turn it upside down and spray the bolts down the sudden freezing from the co2 blast then quick thawing once it evaporates breaks the rust up then when you spray it with some penetrating oil the oil can actually get to the threads and bust the rest of the rust loose (sometimes oil is not even necessary after freezing but i hate drilling out broken studs so i still do it as a precaution)

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That is a *great* tip. Thanks! I gotta try that just to see it work. :-)

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Originally Posted by PartTimeScrapper

Its magic?

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(nerd mode activated)
I'll never join the dark side!
(disengage nerd mode)

yeah when i learned the canned air trick it amazed me, you may have to freeze them a couple times for it to work, and still be careful because rusty bolts can still be broken but i know i have taken many exhaust bolts loose that should have broken from all the rust by doing this trick and its safer than a torch when your working on a car that a customer wants to drive home in when your done.