Corrosion inhibition of zinc by calcium exchanged beidellite clay mineral: A new smart corrosion inhibitor

• Development of eco-friendly corrosion inhibitor based on Ca2+-exchanged beidellite.
• Improvement of corrosion inhibition by progressive release of Ca2+ from host mineral.
• Role of beidellite in trapping aggressive corrosion species such as Cl−, Na+ and H+.
• Valorization of natural Moroccan clay mineral.
• Ca2+-BDT modified the physicochemical properties of electrolyte near zinc surface.

The corrosion inhibition performances of zinc immersed in 0.1 M NaCl solution with and without CaCl2, Na+ and Ca2+ exchanged beidellite (BDT) clay mineral picked up from Agadir bassin (Morocco) was studiedby potentiodynamic measurements and electrochemical impedance spectroscopy. The chemical and microanalysis of Na+-BDT and Ca2+-BDT by different techniques reveal basal distances of clays, of about 1.22 and 1.48 nm respectively, consistent with the saturation of beidellite interlayer spaces with Na+ and Ca2+ ions surrounded by one and two equivalent layers of water respectively. EIS results and surface analysis show that Ca2+-BDT acts as a smart inhibitor on zinc surface by modifying the physicochemical parameters of electrolyte near the surface. The exchange reaction in BDT involves the concentration decrease or the “suppression” of Na+, CO32- and Cl− ions near the zinc surface.