LG&E sent us a letter stating that our cast iron gas pipe bringing gas into the house was rusting and needed to be cleaned and painted. The letter went on to say it was our responsibility to maintain our pipes and by not doing so could lead to gas leaks.
So one of the generous residents of our neighborhood that works for a paint company gave us some gray paint even though they did not have to and we got to work. Once I had brushed and sanded the rust off the pipe, my wife painted it. I think it turned out very well.