Let me be clear: the pins are not stain-less, they do rust. Really.
I have perhaps 7 years experience with pin finishers. I've left the
pins in the solution far too long at times with results similar to
Rahuls problem. Cleaning with Coca-cola works Q.E.D. I won't argue
the point that there are magnetic "stainless steel" alloys out
there. Fact is: the pins rust.
Let me be clear, the fact is that all stainless steel rusts. From
the Wikipedia entry on stainless steel:
In metallurgy, stainless steel (inox) is defined as a ferrous
alloy with a minimum of 10% chromium content. The name
originates from the fact that stainless steel does not stain,
corrode or rust as EASILY as ordinary steel."
Given the right circumstances, and the abrasive action of the pins
and work rubbing on each other and the alkaline nature of the soaps
set this up nicely. The phosphoric and citric acids in the cola
remove the rust.
With regards to magnetism here is the scoop from
Magnetic permeability is the ability of a material to carry
magnetism, indicated by the degree to which it is attracted to
a magnet. All stainless steels, with the exception of the
austenitic group, are strongly attracted to a magnet.
Fact is pins do rust and they are stainless steel
James Binnion Metal Arts