Epoxy is THE best thing for coating bare steel, but as far as cure rate goes, it can be a bit unforgiving. I would suggest that everyone doing refinish work in colder weather buy an
infrared thermometer. I have one now and couldn't live without it during the winter. It's really important to keep metal temps above 60°F, As Barry says you can go down to 55° but in my experience the cure rate is VERY slow below 60°, plus there is always a margin for error, and as far as I know, somewhere in the mid 50's, catalyzing of the material just plain STOPS.