Application of PEO113–b-PS218 nano-aggregates for improved protective characteristics of composite zinc coatings in chloride-containing environment

This study reports on the influence of a very low concentration of polyethylene oxide–b-polystyrene nano-aggregates (PEO113–b-PS218 micelles of 0.5 g/l in the starting electrolyte) on the corrosion behavior and surface characteristics of zinc coatings in chloride-containing environment (5% NaCl). Both zinc (Zn) and composite Zn-polymer (ZnP) coatings were electrodeposited from slightly acidic electrolytes with a coating thickness of approximately 8 μm. The involved experimental techniques were electrochemical methods (potentio-dynamic (PD) polarization, EIS and SVET) and surface analysis techniques (SEM, EDX, XRD and XRF). The morphology, distribution and size of the PEO113-b-PS218 micelles were investigated in demi-water by TEM and dynamic light scattering (DLS), prior to their co-deposition within the metallic zinc matrix.The electrochemical behavior was studied on certain intervals (from initial measurements after OCP stabilization up to 480 h of immersion in 5% NaCl). The recorded parameters account for higher corrosion resistance of the nano-composite (ZnP) coating, compared to galvanic Zn, especially after prolonged periods of treatment. The superior performance of the composite ZnP coating in the very aggressive medium of 5% NaCl is denoted to the combination of increased barrier effects (in the presence of the nano-aggregates) and “self-healing” mechanisms (as a result from a reversible shrinkage and swelling of the polymer shells in the presence of chlorides).