Steel Sweat when Heated -- What?

rhmc24

When steel is heated, my old flint pistol barrels with Mapp Gas torch, at some point it 'sweats' momentarily, which quickly evaporates. I assume the sweat is moisture driven out of pores in the metal. I put on Johnson's paste floor wax in belief that wax will better protect from rust than if waxed over a cold barrel. It seems to work the past 50 or so years. Discussion of water displacing oil started me thinking about it.

Does anyone else do this? I've never heard it mentioned before. Comments, analysis, theories, experience dog & pony stories appreciated.

11b6r

Water is coming from the flame, not the steel. Burning any hydrogen based fuel in oxygen (air- 21% O2) makes water vapor. When the steel is cold, it will condense on the steel. When steel heats, water disappears- as steel is no longer cool enough for water to condense.

When we use portable propane heaters as temp heat in a construction project, a major problem is getting water vapor OUT of the building.

charliemeyer007

Are you sure it's not just condensation from the combustion. I just use WD-40 for the last 40 years.

Jim Rehm

The momentary sweating is probably a result of combustion products from the torch condensing on the relatively cold metal.

BGHillbilly

+1 It's condensation not sweat.

rhmc24

Maybe it is just condensation of flame against cold steel but it seems to occur as the steel heats rather than the instant of heat against cold steel - seems to need the steel to heat up a bit before I see it.

Smoky14

If it has worked for the last 50 years; I don't think I'd change anything now, but a interesting inquire none the less.[:D]
Smoky

He Dog

After cleaning freckling off older rifles I use Trewax to retard the return of rust. Seems to help.