The adsorption and inhibition behaviors of an organic corrosion inhibitor (C12) on the surface of the carbon steel in chloride solution were systematically investigated by using electrochemical measurements. The results indicated that C12 exhibited inhibition and curative effects on the depassivation steel in the presence of chloride. The inhibition efficiency (IE) of C12 was also studied at different temperature. It was seen that the IE was enhanced with an increase in C12 concentration. The Gibbs free energy (ΔG) calculated based on the proposed isothermal adsorption formula for the adsorption process showed that the absorption of inhibitor on steel surface including stably chemisorption. XPS and AFM analyses suggested that after C12 being incorporated, the C12 molecular was tightly adsorbed on the steel surface, resulting in a dense layer formation. This study provides an insight into better understanding of corrosion inhibiting mechanism of C12 in the chloride solution.