[Elecraft] K3S stainless screws

[Howard Hoyt]

Properly done, hot-process black oxide finish on plain steel with a wax 
sealer can be quite corrosion resistance, there is even a MIL spec for 
that (well, there is for everything including waffles, I suspect!).  I 
would think that accounts for the reports of the plain steel screws not 
corroding.

Interestingly enough a reason a black oxide or especially black zinc 
finish is applied to stainless steel is not related to appearance nor 
corrosion resistance, but to forestall galling.  The combination of the 
intervening layer (>0.0002" of black-zinc conversion coating, 0.000005" 
for hot-process black-oxide) and the wax or other sealer aids in 
lowering interface friction.  And although the wax acts a an EP 
lubricant while tightening, it's stiction characteristic can aid in 
fastener retention.

Howie - WA4PSC