I noted John comment and must admit that I had never heard that the old timers used 'tin' pans - I have heard the expression 'To use a tin pan to pan gold' but they also used 'tin cans' to preserve foods - in truth I would highly doubt that tin pans were made of tin - at the outside they might have been tin plated but the plating would wear out within an extremely short time - tin cans were not made of tin either. Tin cans were made of sheet steel and tin plated only.
Old time pans were made of the best quality of Russia iron, stamped out of a single sheet, with the edge turned over a stout wire. (Nevada-outback-Gems.com)
As I said in my last contribution above the old chap who came gold mining with me had spotless pans, shiny and well preserved without one speck of rust. These pans were extremely old ones having come down through his family before him as his father (died 1904) and his grandfather (One of New Zealands pioneer miners) were both well known in mining circles - he used them during the depression era for week end panning and was still using them up until he was around ninety years of age.
The secret was simple - when it was the end of the day it was dried and it was kept dry. They were not stored in a damp environment, left on the ground under the cellar or in any other damp location but hung up as he had leather straps riveted to them for carrying.
The thing that kept them rust free was simply caring for them and never leaving them wet or in a damp place.
I guess most guys on here are like me - use them and abuse them, leave them outside the hut, boil water in them, use them to wash the dishes and then throw them onto the tray of the truck to fill full of rain and exposed to the elements. I also learnt the hard way that heating them red hot seems to promote rusting!