On Fri, Jan 1, 2016 at 8:23 PM, Bill Rutherford <xxxxxx@comcast.net> wrote:

https://www.newscientist.com/article/mg15520981.600-space-is-corrosive/ (a 1997 link cited in the previous link that's pretty interesting)

So . . . it seems that the answer to the OP's question lies in comparing how much oxygen a sheet of iron is exposed to at sea level, versus the 10 to the 16th atoms of atomic oxygen per second per square centimeter which the relevant bits of a satellite is exposed to in low earth orbit (which is - apparently - not quite an actual vacuum).

<googling . . . >

It seems that given 1 atmosphere of pressure and a temperature of 298 Kelvin, there are 2.64 x 10 to the 25th atoms of oxygen per cubic meter.

I'm not precisely sure how that would convert to a comparable exposure rate. As there are a million cubic centimeters in a cubic meter, I think we would need to reduce that 10 to the 25th to 10 to the 19th. But we don't know how many of those sea level atoms get a chance to react with the iron. Would ambient air movement be enough that all of them would?

Of interest is that the article notes that "no satellites have been crippled by atomic oxygen." Since some of the effected satellites have been up for decades, while exposed iron at sea level can rust markedly in a matter of days (depending upon exact conditions) . . . I would say that the answer is something like: "Iron in low earth orbit corrodes very, very, very, very slowly." 

-- 

Richard Aiken

"Never insult anyone by accident."  Robert A. Heinlein

"A word to the wise ain't necessary -- it's the stupid ones that need the advice." - Bill Cosby

"We know a little about a lot of things; just enough to make us dangerous." Dean Winchester

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