I had a steel bike on the trainer for years, no fan, no sweat guard. I have corrosion everywhere - on the frame as well as on the (aluminum) cranks. The combo of a sweat guard, a fan and a towel besides me that I use every 5-10 minutes have solved the problem. I did a complete overhaul of the dedicated trainer bike last week, and apart from the salt mine hiding under the bar tape, it was all good.