I absolutely love my old tinware, especially the frying pans. Like my cast iron, the tin is versatile too. I can take it from the stove, to the fireplace, to the grill or the campfire.
However, every once in awhile a pan gets some rust. Either it didn't dry well or somehow got some dampness in it that sat.
I have found that I can save the pan if it isn't too awfully bad, with a steel wool soap pad and vegetable or olive oil.
I simply clean the rusted area with a little water and the soap pad. This may take a few washings. In between washings, dry quickly on a warm stove burner. When rust has gone, generously rub the surface with the vegetable or olive oil and let sit for a few hours. Then, wipe out any oil that may be "floating" yet in the pan. The pan should not be wet with oil when you put it away.
When you put the pans away, layer waxed paper between to keep bottoms clean. It also doesn't hurt to do this occasionally as a rust prevention step.