That would be the study of friction and wear of components. In watches I concern myself with this everyday but we don’t always think about it on the outside of the watch.
When gold fights with steel, steel always wins, right? Wrong!
You will notice that on this Rolex Steel & Gold Bracelet the steel spring bar wore heavily at the point where it contacts the gold center links (click on the picture for a larger view). If we were dealing with a clean bracelet the soft gold would wear a very little bit against the steel spring bar, but in the case of this very dirty bracelet what happens is that dirt and grime embed themselves in the soft gold turning it into an abrasive which tears apart the steel springbar. In this kind of “dirty” situation the soft metal always wins. You will notice however that where gold rubs against gold (2nd link from the right), both lost in this case. Both equally become embedded with grime and they abrade each other equally because the metal is still soft.
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