Two new cationic surface-active compounds namely; N,N-dimethyl-N-(3-tetradecanoamidopropyl)-1-ammonium
bromide and N,N-dimethyl-N-(3-hexadecanoamidopropyl)-1-ammonium bromide referred as (ACS3.1 and ACS3.2),
respectively were synthesized and their chemical structures confirmed by spectra tools (FT-IR and 1H-NMR). The
inhibition effect of the synthesized cationic surfactants on carbon steel in 1 M HCl solution was evaluated using weight
loss and potentiodynamic polarization methods. The study show that cationic surfactants (ACS3.1 and ACS3.2) are
excellent inhibitors even with very low concentration and their adsorption on carbon steel surface obeyed Temkin
adsorption isotherm. The polarization measurements indicated that the two synthesized surfactants acted as mixed-type
inhibitors. Thermodynamic parameters were obtained from weight losses at various temperatures and discussed.