Caffeic acid was investigated as an inhibitor for aluminum-silicon alloy corrosion in 1.0 M solution of hydrochloric acid. Weight loss, Tafel polarization, and impedance spectroscopy techniques were used in the study. The data showed that caffeic acid act as an excellent inhibitor for acid corrosion of the aluminum alloy. The inhibition efficiency was found to be increased with its concentration but decreases with increasing temperature. The inhibition process was attributed to adsorption of the inhibitor molecules on the alloy surface. The adsorption is physical in nature and follows Langmuir adsorption isotherm. Thermodynamic functions of the corrosion reaction were determined and discussed.