Analysis of the synergistic effect of sodium molybdenum oxide and vanillin on the corrosion inhibition of high carbon steel and 3CR12 ferritic stainless steel in 2M HCl solution was done through coupon measurement, potentiodynamic polarization test and IR spectroscopy. Results show the admixture compound inhibited the corrosion of both steels, but performed more effectively on 3CR12 ferritic steel with average inhibition efficiency above 90% while the average inhibition efficiency of the compound on carbon steel was around 75%. Polarization studies showed mixed inhibiting properties of the compound on the carbon steel and anodic corrosion inhibition on the ferritic steel. The compound adsorbed over the entire carbon steel surface, but selectively precipitates at anodic sites on the stainless steel surface due to the passivation characteristics of the steel. Chemisorption mechanism was determined from thermodynamic calculations to be the mode of inhibition on the steels through the Langmuir adsorption isotherm. Infrared spectroscopy exposed the presence of the functional groups and bonds such as alcohols, phenols, primary and secondary amines and amides within the compound responsible for corrosion inhibition.