Effect of Aging Time of Sulfuric Acid Cleaning Solution Containing a Surface Activating Agent on Protective Performance of Silane Coating

The stability of acid treatment solution containing 100 ppm hydrogen peroxide, as a surface activating agent and 1 mM benzothiazole, as a corrosion inhibitor during 12 days of storage was investigated using electrochemical impedance spectroscopy (EIS), polarization test, high resolution scanning electron microscopy (HRSEM) and atomic force microscopy (AFM). The results of EIS and polarization showed that in the presence of H2O2, corrosion resistance is much less than the one contains no H2O2 after aging. According to the results of HRSEM, corrosion products became denser and more porous. Surface roughness increased over aging time and therefore confirmed the previous results. In the following, protective performance of silane sol-gel coating applied on mild steels treated in acid solutions in both fresh and stored conditions was examined using EIS. It was founded the coating resistance decreased during storage. However, the coating on the surface treated by fresh acid solution containing H2O2 had the superior protection compared to the one containing no activating agent.