corrosion de clef de voûte

OBS: Corrosion observée à la partie supérieure (ou au sommet) d'un égout.
OBS: «crown» (arc, route, voûte) : «sommet».
OBS: «crown» («of an arch») : «clef de voûte».

CONT: Sulfates in sewage can result in offensive odors from the formation of hydrogen sulfide gas, with its characteristic rotten-egg odor. It also leads to a problem in sewer systems called crown corrosion.
OBS: ""crown"": The inside top of the arch in a sewer, covered channel, or conduit.