There are a couple of things about galvanic corrosion that blows kionrads theory out of the water.

1.  Galvanic corrosion occurs where disimilar metals are touching.   So the corrosion would not occur at the surface of the race, but where the steel is contacting the aluminum case.

2.  Galvanic corrosion always causes the less noble metat to corrode while protecting the more noble metal.  In pipelines sacfrifical anodes are connected to the pipe at regular intervals.  They are usually zinc and the zinc corrodes requiring them to be dug up and replaced at regular intervals.  In the case of steel bearings of any grade steel and a aluminum case the aluminum is the less noble metal and the one that will corrode.