Grade 8 vs Grade 5 Bolts

That's minimal yielding there to compensate for tolerances and such. The point is to have sufficient ultimate strength and to maintain preload in the bolted joint. Without preload the bolt must carry 100% of tension load on the joint.

makes sense - the microsopic surface would then be a choppy field of carbon bits poking up. Little holes for water next to electric rods. That kind of dovetails with the theory given for lowered corrosion rates of lapped steel, a process which smears the surface

thanx..