Corrosion Behavior and Sacrificial Properties of Zn and Zn-Al Coatings in Conditions Simulating Deep Geological Disposal of Radioactive Waste at 80 °C

In France, it is planned to manage high-level radioactive waste via deep geological disposal. The carbon steel overpacks containing the will face corrosion processes specific unusual environment of To protect these against corrosion, use metallic sacrificial coatings was considered as a possible solution. Therefore, behavior thermally sprayed Zn and Zn-15wt.%Al (500 µm thick) studied in solution simulating Galvanic experiments were performed with coated electrode connected bare one, which simulated coating defect. First, observed that had lost its properties after ~2 months coupling. XRD µ-Raman analysis carried out experiment demonstrated covered protective hemimorphite (Zn4Si2O7(OH)2·H2O)-rich layer. contrast, kept all along 6-month experiment. It proved be layer mainly composed Zn-Al hydroxysulfates, did not contain hemimorphite. However, SEM cross-sectional observations showed electrolyte seeped into even reached surface. This infiltration led oxidation splats inside coating, close surface, induced large swelling coating. Its thickness increased by 50%.