Corrosion Behavior of Tin-Plated Carbon Steel and Aluminum in NaCl Solutions Using Electrochemical Impedance Spectroscopy

The corrosion behavior of both tin-plated carbon steel and aluminum (Al 1100) in NaCl solutions were studied using electrochemical impedance spectroscopy (EIS). The study objectives were to compare their corrosion behavior in concentrated brine solution, establish the equivalent electrical circuit diagrams of their corrosion phenomena, and consequently develop steady-state corrosion models for estimating the corrosion rates in the given solution. The steady-state corrosion rates for the tin-plated carbon steel increased significantly when the concentration of NaCl was increased from 1.0M to 1.5M. The increase in corrosion rate of the tin-plated steel is attributed to reduced charge transfer resistance due to the breakdown of the surface tin plating at high chloride concentrations. In contrast, there was little incremental change in the corrosion rates of aluminum when the NaCl concentration was increased from 1.0M to 1.5M. This is attributed to the known formation of a stable, passivating surface oxide film on aluminum which inhibits corrosion. The surface passivating film did not show any significant evidence of degradation with increase in chloride concentration. Using MATHLAB and the experimental corrosion rate data, a mathematical corrosion model was derived for the two samples to describe their steady-state corrosion in NaCl electrolyte solutions.