Analysis of Soft Coating Corrosion Performance on Carbon Steel Using Electrochemical Impedance Spectroscopy

Electrochemical impedance spectroscopy (EIS) was used to characterize the performance of rust preventives (soft coatings) formed on the surface of metal in different electrolytes. ASTM B117, the accelerated salt spray corrosion test, was also used to characterize the films with a 5 wt% sodium chloride (NaCl) solution. The results obtained by both methods were compared and used to explain the degradation occurring at the film/steel substrate interface. EIS was used to quantify and characterize transport mechanisms and correlate the magnitudes obtained by the film's damage evolution due to three electrolytes {3 wt% NaCl, 5 wt% NaCl, and 1.15 wt% ammonium borate [(NH4)3BO3]}. ASTM B117 and EIS were used to determine the performance of six different rust-preventive samples based on the damage evolution. The experimental and analytical results indicate good correlation between each method.