Corrosion Protection Studies of Crude Glycerol-Based Waterborne Polyurethane Coatings on Steel Substrates

Crude glycerol (CG), a low-value byproduct from the biodiesel industry, has a significantly different composition compared to pure glycerol. Generally, crude glycerol contains various impurities, such as methanol, water, soap, free fatty acids (FFAs), fatty acid methyl esters (FAMEs), and glycerides. In this study, the performance of crude glycerol-based waterborne polyurethane (PU) coatings synthesized using crude glycerol as a sole feedstock via a thermochemical conversion process was studied. The corrosion properties of coatings were characterized by electrochemical impedance spectroscopy (EIS), polarization measurement and salt spray test. The experimental results show that crude glycerol-based PU coatings have a considerably enhanced corrosion resistant performance of metallic substrate (phosphated steel).