The invention relates to an outer coating (9) for an underground piping member (7) made from iron, in particular cast iron, the outer coating comprising a first porous layer (11) and a second porous layer (13) positioned on the first layer and capable of plugging the pores of the first layer (11). The first layer comprises substantially pure zinc or an alloy or pseudo-alloy of zinc, the alloy or pseudo-alloy comprising at least 50 wt % zinc, and preferably between 0.5 wt % and 40 wt % aluminum. The second layer comprises a paint with a base of at least one organic resin, the paint being either single-component in an organic solvent or co-solvent, or dual-component. At least one among the first layer and second layer comprises a bactericidal agent.The invention also relates to a corresponding coated piping member and method for depositing the coating.