Siezed Up / Rusted Nuts And Bolts?

[Theland1]

What happens when over a period of time, a nut becomes rusted almost solid to a bolt?
The rust is soft as I can crumble it between my fingers, but I often have to use Plus Gas and a flogging spanner with a big hammer to get the nut and bolts apart.
(20mm nuts and bolts and above).

[Clanad]

It has a lot to do with the original quality of the nuts and bolts, Theland... If the bolts are going to be in a rust conducive location, it's best they be at least galvanized, but even better would be stainless steel. The rusting action acttually welds the two parts together over a period of time. (By Plus Gas, I'm supposing it's the Brit example of a small blow torch powered by propane or some sort). But as far as a flogging spanner... the only thing I deciper is a spanner is what we call a wrench. But a flogging spanner? Haven't got a clue! I've had bolts on ranch equipment here in the western U.S. that have had to be cut off with a good cold chisel and two pound sledge hammer or even an acetylene cutting torch.
Good to see you back, by the way. I hope things are going better. I'd be happy to talk to you about that, but that would be difficult in this type of a forum. At any rate... Good luck!

[wildwood]

The rust initially only happens on the surface of the metal. In the limited space of the thread the oxidisation expands and virtually locks the two together. This also means that no oxygen can reach the space and so the chemical reaction stops there but the outside of the bolt/nuts will continue to be exposed to air and so rust further.
This can be validated by considering a rusty scew in wood. It always breaks close to the head as the end is not usually subject to oxygen so can not rust.

[Theland1]

Clanad, thanks for your kind sentiments.
Plus Gas is a spray on chemical that dissolves rust and helps release the nut and bolt.
A flogging spanner is a single ended ring spanner with a short handle and a steel block on the end to take the hammer blows.
I've been confronting these problems for 41 years but never stopped to consider why at times we had to resort to heat or a cold chisel / nut splitter.
On a similar theme, we always apply, "Copperslip" paste to prevent this happening in the future.

[heathfield]

I've never been at all impressed with the results from using PlusGas. Personally, I've found brake fluid to be a better means of helping to free up rusted nuts and bolts.