Electrochemical Corrosion Potential Abatement of 304 Stainless Steel Coated with ZrO2 Nanoparticles under Boiling Water Reactor Operation Conditions

The search for novel materials to protect stainless steel from corrosion at different working conditions has attracted researchers' attention worldwide, where ZrO2 has been of great interest. In this work, the effect of a coating of ZrO2 nanoparticles smaller than 5 nm on the electrochemical corrosion potential-standard hydrogen electrode-(ECPSHE) of 304 stainless steel (304SS), at boiling water reactor conditions, is presented. A ZrO2 coating was applied over the surface of oxidized specimens of 304SS, by deposition of ZrO2 nanoparticles with mean size of 3.75 nm. The ECPSHE of this system was determined under BWR operation conditions, through polarizing tests. It was possible to abate ECPSHE to less than - 230 mV, which is enough to protect 304SS against stress corrosion cracking. The effect of ZrO2 nanoparticles concentration on the coating characteristics and on the electrochemical performance was evaluated. Coatings were analyzed by transmission electron microscopy, scanning electron microscopy, energy dispersive x-ray spectroscopy (EDS) and by x-ray diffraction. The optimal concentration determined and the size of synthesized ZrO2 nanoparticles, allowed to obtain a coating without cracks, forming a ZrO2 physical barrier for oxidant species to avoid water and oxidants reach the 304SS surface.