This article describes an investigation of the corrosion behavior of carbon steel in 2M HCl solution with the addition of some cyanoacetohydrazide derivatives by weight loss, galvanostatic polarization, and potentiodynamic anodic polarization techniques. The explored methods gave almost similar results. Results obtained reveal that inhibitor (I) is the best inhibitor and the inhibition efficiency (IE%) follows the sequence IIIIIIIV. The percentage inhibition efficiency was found to increase with increasing concentration of inhibitors and decreases with increasing temperature of the medium. The addition of KI, KSCN, and KBr to cyanoacetohydrazide derivatives enhanced the inhibition efficiency due to synergistic effect. The effect of temperature on C-steel corrosion in 2M HCl and with the addition of 11x10-6M of investigated compounds in the temperature range 30 degrees-50 degrees C was studied. Some thermodynamic functions were computed and discussed. The inhibitors are adsorbed on the carbon steel surface according to Temkin's adsorption isotherm. Polarization data suggested that the additives used act as mixed-type inhibitors. It was found that the cyanoacetohydrazide derivatives provide good protection to carbon steel against pitting corrosion in chloride-containing solutions.