The lock geometry seems to lend some self-cleaning capabilities to the knives, as the lock bar can push away any dirt or debris that's on the blade tang. I don't get mine too dirty but I think the Axis lock is near the top in terms of locking system designs that tolerate debris.
Of course, your washers are going to feel awful when they get dirt in them, but just about any knife short of a MUDD will. The locking system should still function 100%.