SYNTHESIS AND STUDY OF METAL OXYNITRIDES THIN FILMS FOR ANTICORROSIVE APPLICATIONS

Abstract

Corrosion is the deterioration of materials due to the continuous reaction of the materials to the surrounding environment. This event is occurring in all kinds of materials, either natural or manmade. The prime impact of such a reaction is the loss of functionality of metals in various applications. Corrosion of metallic material causes high economic losses and fatalistic catastrophe, which can be observed from the different survey studies, cost of corrosion is estimated to be around 3.4% of the national gross domestic product (GDP). Along with these, corrosion products are responsible for the deterioration of quality in the food and pharma industries. It leads to grievous effects due to environmental pollution. The solution to the corrosion problem is explored in an interdisciplinary way among material science, metallurgy, physics and chemistry with many more. In the same direction, in the last decade, various methods of overcoming corrosion issues were developed. The common among them was chemical conversion coating, alloying, organic/inorganic barrier coating and use of corrosion inhibitors. Coating-based solutions to corrosion problems became effective, cost-effective and easy to implement in comparison to others. For the coating, the physical vapor deposition method provides a low impurity and eco-friendly route to deposit the nanoscale materials with tunable surface morphology. The features help in the enhancement of the anti-corrosive performance of the coatings. Researchers have investigated various metal oxides i.e. TiO2, ZrO2 and HfO2, metal nitrides i.e. CrN, MoN, TiN and ZrN, metal carbides i.e. WC, Cr3C2 and SiC and many more compounds of metal as an effective anti-corrosive coating. The understanding of the factors affecting the corrosion rate is very important, which leads to better control over them. Effective implementation of research study results in the fields can hamper the detrimental effects of corrosion on health, economy and environment. The prime objective of the present dissertation was to synthesize different transition metal oxynitride thin film materials such as Tantalum oxynitride, Vanadium oxynitride Titanium oxynitride etc. by physical vapor deposition (PVD) technique i.e. reactive magnetron sputtering. To investigate the corrosion behavior concerning different factors/conditions i.e. salinity, pH, availability of dissolved oxygen in the electrolyte, temperature etc affecting corrosion rate and protection of different industrial base metals like stainless steel, aluminum alloys etc. Optimized deposition conditions result in the deposition of films with very good uniformity and nanoscale roughness, which affects the interaction at the surface-electrolyte interface. The coating surfaces with low roughness exhibit hydrophobicity and in turn support the anti-corrosive nature of the coatings.