The influence of Clotrimazole (CMZ) on corrosion and hydrogen permeation through Stainless steel 304 in 2N H3PO4 and 2N HCl has been studied using weight loss measurements and various electrochemical techniques. The inhibitor is found to be more effective in retarding the metal corrosion in H3PO4 than in HCl. Potentiodynamic polarization studies clearly indicate that CMZ behaves as a mixed inhibitor. Hydrogen permeation studies and AC impedance measurements also proved an excellent performance of the compound in H3PO4. The adsorption of this compound on the mild steel surface obeys Temkin's adsorption isotherm which is further validated by Quantum chemical calculations. © 2014 University of Manchester and the authors.