Thiocarbamides namely thiocarbamide (TC), ethylenethiocarbamide (ETC) and thiobenzamide (TBA) have been used as corrosion inhibitors for (70/30) brass in 0.1 M HClO4. The inhibitor efficiency (% P) calculated using weight loss, Tafel line extrapolation, linear polarization and impedance methods has been found to be in the order: TBA > ETC > TC. Thiocarbamides adsorbed on the electrode surface inhibited the corrosion of brass. They adsorb following Flory-Huggins isotherms. The number of water molecules displaced was found to increase with molecular size. TC, ETC and TBA displaced 3, 4 and 10 molecules and caused a distortion at the metal solution interface. The inhibitor molecule may form complexes with the dissolved Cu and Zn ions. This may result in the formation of a film.