My guess is it has something to do with the scales. I'd bet the problem begins there. Maybe the scales need to be passivated too.
My halperin scales are never used in conditions like that so I wouldn't know yet if they are the same way.
The dust is difficult to see and I've found it still on blades after washing them in soap and water. It takes usually a good waxing with a soft clean cloth to get that tiny particle stuff off as much of it is magnetized and stuck to the steel in the grooves left from polishing we need a microscope to see. Commercial outfits often use an acidic(?)base(?) solution to get metals passivated. Even Titanium can have problems if contaminated.
Joe