Performance of corrosion protection of carbon steel with cerium modified phosphate–permanganate coatings and a layer of silane doped with cerium

Abstract

This work was aimed to evaluate the effect of bis-[triethoxysilylpropyl] tetrasulfide (BTESPT) doped with cerium nitrate, as a corrosion inhibitor, on improved corrosion resistance of samples of carbon steel with a phosphate–permanganate layer in a 0.5 M NaCl solution. The main goal of the present work was to compare self-healing capacities of cerium conversion coatings and cerium as an additive inhibitor to silane. The composition and structure of the investigated samples were characterized by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) techniques, while the corrosion behaviour was investigated applying voltametric and electrochemical impedance spectroscopy (EIS) measurements. The results of EIS measurements performed during 24 h immersion of the investigated samples into the 0.5 M NaCl solution revealed that the layer of silane doped with Ce was more protective than that of the non-modified one. It has been determined that the presence of cerium nitrate in the silane coating can lead to high values of low frequency impedance due to the healing of the defect.