The oil can finish is a cosmetically unique hot oil oxide process applied to the wedge that will wear off over time leaving a raw finish.  As this finish wears off, it will leave a raw wedge which will rust over time.  You can apply a thin coat of baby oil on it and keep the wedge dry after playing and this will help prevent it from rusting. 

As they fade i have found that they get a little but softer and even produce a little bit more spin. I would just let them ware!