The only criteria I can think of that might apply is from ASTM A6. Section 9.3.1 of that spec gives a limit for "injurious imperfections or surface depressions". For a W27 x 281 the limit seems to be 1/16" max. before repairs need to be made.
It is difficult to quote the spec in this forum and I don't want to lead you astray, so by all means, get ahold of a copy to read for yourself. But, I think it might be helpful to you.

CHGuilford

I entirely agree with Mr. Guilford's opinion. A word of warning: are the columns painted or not? If you're supposed to paint them, then, considering that they're pitted, the minimum surface preparation would be "sandblasting to near white metal".
Giovanni S. Crisi
´Sao Paulo - Brazil