The effect of new corrosion inhibitor namely 1H-1,2,4-Triazol-4-amine,3,5-diphenyl-N-phenyl methylene) (HTADP) on the corrosion of brass in NaCl 3% medium pure and polluted by the yeast (eukaryotic microorganisms) as corrosion inhibitor has been studied by using electrochemical techniques such as potentiodynamic polarization and electrochemical impedance spectroscopy. Results obtained showed that the yeast accelerate the alloy corrosion. And a significant reduction of corrosion rates was observed in both media in the presence of the (HTADP). The inhibition efficiency reaches 90% at a concentration 10-3 M of (HTADP). The effect of biocide, namely cetyltrimethylammonium bromide (CTAB), on the inhibition efficiency of (HTADP) has been studied, too.