And it's hard to think of anything made of latex that would be corrosiveIf it'd make a difference... the latices in question would probably be
things like unfinished (i.e., uncoagulated) styrene-butadiene or other
synthetic rubbers. The liquid output after the ingredients (styrene and
butadiene for SB rubber, aka GR-S or Buna-S) are co-polymerized (using
other chemicals as catalysts, emulsifiers and retardants) is called a
latex; the latex is then fed into another tank, where it's mixed with
brine and sulphuric acid to make it coagulate into little flakes of
solidified rubber that's then baled and shipped off in 40lb bales (likely
the contents of the UP boxcar I saw in another photo of the Polymer Corp.
Now, whether this latex described above would be corrosive or otherwise
dangerous to put into an unlined tank car, I don't know... perhaps someone
who understands polymer chemistry a bit more could answer that.