Influence of Waste Material Additives on the Performance of a Novel Hybrid Sol-Gel Coating on Mild Steel in 3.5% NaCl Medium

This article presents the synthesis of a novel hybrid sol-gel coating and its functionalization with various waste material additives. The unmodified and modified hybrid coatings were deposited on mild steel (MS) substrates, and their anticorrosion performance in a 3.5 wt.% sodium chloride corrosive environment was assessed using potentiodynamic polarization and impedance electrochemical techniques. The Fourier Transformed Infrared Spectrometry (FTIR) spectral, thermal, surface-roughness, scratch-resistance, and contact-angle characterizations were also conducted on the fabricated coatings. Electrochemical techniques proved that the coating sample loaded with the limestone additive showed the best anticorrosion behavior in the saline environment after 4 weeks of exposure. Moreover, the obtained morphological analysis data indicated better surface integrity and cross-link density for this sample compared to other waste-modified coatings. Conversely, the tire rubber and activated carbon additives showed a severe negative impact on the thermal, mechanical, and barrier properties of the parent coating, which can be attributed to the high porosity and less integrated natures of these modified coating formulations proved by their morphological images. Still, all loaded waste additives to the hybrid coating have enhanced its adhesion to the steel surface, as indicated by scratch resistance testing. Overall, the results of the present study show the need for maintaining a balance between the economic value of the modification methodology of hybrid coatings and the type of the loaded waste material additive.