High performance specialized coatings for applications in corrosive environments

Abstract

In this paper a short review of various coatings developed based on facile as well as industrially scalable methods and the challenges encountered in enhancing the durability of the coatings in simulated service conditions are presented. These coatings include (i) development of noble metal (Pt/Pd) nanoparticle coated titanium electrodes for electrochemical processes employed in spent nuclear fuel reprocessing, and (ii) development of superhydrophobic (SHP) coatings on titanium, stainless steels, low-chromium steels and copper alloys to address corrosion and biofouling issues in chloride environments of condenser materials in nuclear power plants. Nanostructured noble metal (Pt, Pd) coatings on Titanium and titania nanotube for electrode applications were developed using a novel seed mediated coating technology involving electrodeposition assisted hydrothermal method. Studies demonstrated that by engineering the particle size of Pt, and nano-tubular self assembled arrays of TiO2 (TiNT), the electrocatalytic activity for methanol oxidation could be enhanced ten times compared to polycrystalline Pt. By employing electrochemical cerium oxidation studies, excellent durability of this Pt nanoparticles coated TiNT electrode surpassing 1000 h in 11.5M nitric acid was also demonstrated. In the second part of the manuscript development of SHP coatings to address corrosion and biofouling issues in chloride medium of condenser materials such as titanium, stainless steels, low chromium steels and copper alloys is detailed. Inspired by the lotus effect two step techniques were adopted for creating a micro-nano roughness pattern, and reducing surface energy by coating with low surface energy material. Micro-nano texturing of different materials was achieved by various methods like polishing, pickling, anodization, sand blasting etc. Attempted different organic fatty acids and silica nanoparticles mixed silane, to enhance durability. Finally durable and stable SHP coatings were demonstrated with high water contact angle and corrosion resistance and reduced microbial attachment indicating superior bio corrosion resitance of the materials studied. Facile techniques were adopted for both coatings in order to support scaling up for real time applications in future.