Water vapour migration through stainless steel
Water vapour migration through stainless steel
(OP)
Hello all,
I read a line a technical manual recently which stated that water vapour can migrate through stainless steel piping. The context is a high pressure (300 bar), very dry (dew point is <-50 deg C), air system. It stated that it is possible for water vapour to migrate through the pipe wall and to therefore be wary of the dew point increasing over time. It did not seem to be talking about migrating through loose/leaking fittings, but through the pipe wall itself.
I have never heard of this before - and could not find any references to it in some quick research.
Is stainless (or any other steel, or metal for that matter) permeable to water vapour? How do coatings (paint, linings etc) affect it?
I read a line a technical manual recently which stated that water vapour can migrate through stainless steel piping. The context is a high pressure (300 bar), very dry (dew point is <-50 deg C), air system. It stated that it is possible for water vapour to migrate through the pipe wall and to therefore be wary of the dew point increasing over time. It did not seem to be talking about migrating through loose/leaking fittings, but through the pipe wall itself.
I have never heard of this before - and could not find any references to it in some quick research.
Is stainless (or any other steel, or metal for that matter) permeable to water vapour? How do coatings (paint, linings etc) affect it?





RE: Water vapour migration through stainless steel
RE: Water vapour migration through stainless steel
RE: Water vapour migration through stainless steel
There can be a lot of moisture absorbed onto the inside surface of a pipe that has been exposed to the air.
On thing that people don't appreciate though is that a very tiny leak in a high pressure line will let impurities IN. the result is that very small leaks can be the source of significant system contamination.
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P.E. Metallurgy, Plymouth Tube
RE: Water vapour migration through stainless steel
Ditto what EdStainless said: if there's a concentration gradient, you'd be surprised how large an advective gradient (pressure difference) molecules can climb up to get into your clean medium. Think salmon swimming up a waterfall.
Smaller molecules like hydrogen and helium can make their way through metals and glass, but water is pretty big.
RE: Water vapour migration through stainless steel