Corrosion is a great concern in the oil and gas industry as it affects the infrastructure in exploration, production, transportation, processing, and CO₂ sequestration. The ability to monitor corrosion online before structure integrity is compromised can have a significant impact on preventing catastrophic events resulting from corrosion. High durability is required for the corrosion sensors in extreme service conditions such as high temperature high pressure during drilling, production, and refining. A recent concept for early corrosion on-set detection involves the use of proxy materials integrated with the optical fiber sensor platform which is relatively inert and immune to electromagnetic interference (EMI). The electrochemical behavior of the proxy material could provide insight into the conditions in which corrosion is expected to occur. The proxy material was deposited on the optical fiber and tested in CO₂ containing 3.5%wt NaCl solution at 30 ^oC. The optical spectrum was measured to monitor the interaction between the proxy material and the environment. The optical spectrum calibrated with the electrochemical results in the same condition can quantify the corrosive environment. The electrochemical method and surface analysis were utilized to characterize the proxy material.