The addition of sulfide ions to a solution of 0.58 M NaCl containing benzotriazole (BTAH) results in a decrease of the inhibiting efficiency of BTAH and a momentary increase of the dissolution rate of alpha brass at potentials above the corrosion potential. The effect depends on the sulfide ion concentration and the potential selected for the tests. The results are explained by decomposition of the protective Cu(l)BTA film, caused by the extraction of Cu(I) ions from the film and formation of Cu2S: nS(2-) + 2[Cu(I)BTA](n) --> nCU(2)S + 2nBTA(-). The breakdown of the film allows metal dissolution from the bare surface and further promotes the effects of sulfide ions.