CO2 corrosion is an important problem of pipeline and refinery processes and carbon capturing & storage (CCS) activity too. One of solutions for CO2 Corrosion and preventing its damage and reduction of its cost is usage of inhibitor. Inhibitor behavior changes with content of corrosion system include electrolyte and exposed metal. Products (scale) of CO2 Corrosion in some case; partial pressure, temperature and pH act as protective layer. Interaction of inhibitor and protective layer and effect of both of them on corrosion rate is important. In this research, corrosion inhibitive effect of “Azole” Derivative’s "2-Mercaptobenzimidazole" on carbon steel (API-5L, material of pipeline) was investigated. Test environment was distilled water with 3.5%NaCl. CO2 gas continuous purged to this electrolyte during tests. Test carried on three temperature; 250 C and atmospheric pressure in static condition. Result of tests revealed that inhibitor have more than 90% efficiency. Mechanism of Corrosion prevention by inhibitor (Anodic, cathodic,…) and adsorption behavior model (Langmuir)have been discussed in this paper too.