I may be wrong, but I believe you mean "galling". Spalling is another thing all together.
russb-there is some damage there that may or may not mean the hardware
is salvagable. The microscopic flakes are the culprit.
Thread galling seems to be the most prevalent with fasteners made of stainless steel
, titanium, and other alloys which self-generate an oxide surface film for corrosion
protection. During fastener tightening, as pressure builds between the contacting and sliding thread surfaces, protective oxides are broken, possibly wiped off, and interface metal high points shear or lock together. This cumulative clogging-shearing-locking action causes increasing adhesion. In the extreme, galling leads to seizing - the actual freezing together of the threads. If tightening is continued, the fastener can be twisted off or its threads ripped out.