Bare and Rusted Steel Beams

[Kenneth A. Townsend]

It will out last the home!

[Marcel R. Cyr]

I wouldn't worry to much about paint in that picture.
Before their is enough moisture in that crawlspace to affect that heavy duty beam, the whole floor would be rotted to hell.

Steel members that will be enclosed in normal ambient conditions, which is most of them—typically do not need to be painted.

The inside environment of most buildings to-day is conditioned for human occupancy (low humidity).
Although the crawlspace is not for human occupancy, I doubt if the relative humidity will be above 70, and if it is, other problems will arise.

Detrimental rusting of steel takes place when the relative humidity is above 70%. Therefore, if steel is to be exposed for a short period during construction and subsequently clad and enclosed, the structural steelwork will not corrode and does not need any paint protection.
Specifying no paint saves the costs for cleaning, painting, inspection, touch-up paint, and the cost of the paint materials

I have built a few School Buildings where the shop primer was eliminated altogether for the whole structure.