Quoted from arolden:Oils in your skin can corrode metal, but this takes a huge amount of time and it won't affect the ball across its whole surface; only where you've touched it. If the balls are rusting all over and over a short period of time, then it is more likely to be caused by the environment or the way the balls were manufactured.
It can depend on the person. Also, ofcourse this isn't within weeks. But maybe after a year. And with rust I don't mean rusted through, just effected. When you hold multiple balls in your hand and roll around you likely touched most of the ball.
It's not difficult, you don't have to clean them with alcohol of something. Just wipe hem off with your shirt or something before putting them back in the game. No need for a special ballrag