I have seen stub axles and axle flanges in a couple of finishes recently. MSA has them for sale refurbished in yellow zinc. Should they be yellow zinc of semi gloss black?

I've seen those also.  I always have thought they were the semi gloss black.  I also think you would still see some of the zinc in the area between the hub and brake drum if they were zinc coated.

The finish is not too important. However the run out, (comsistency of the radius) is much more important. This should be check before installation. If there are high or low spots it will cause premature bearing wear.

15 hours ago, jwtaylor said:

I've seen those also.  I always have thought they were the semi gloss black.  I also think you would still see some of the zinc in the area between the hub and brake drum if they were zinc coated.

I sort of agree. Just trying to verify which way I need to go with the finishing

I would never put paint on a precision machined surface that is supposed to be a metal-to metal mounting, clamping, or reference point.

Might just be me, but a couple molecule thick layer of plating is all I would be comfortable with.