Evaluating the Corrosion Resistance of Nanostructured Coatings in Marine Environments

Thesis Abstract

Corrosion significantly undermines the longevity and integrity of metallic structures in marine environments, necessitating the development of advanced protective coatings that can withstand aggressive saline conditions. This study investigates the efficacy of nanostructured coatings in enhancing corrosion resistance compared to conventional coatings. The primary aim is to evaluate the corrosion performance of various nanocoatings applied to steel substrates in simulated marine conditions, establishing their suitability for maritime applications. The specific objectives include characterizing the microstructural features of the nanostructured coatings, assessing their corrosion behavior through electrochemical testing, and analyzing their durability under accelerated marine exposure. The research adopts an experimental design, combining laboratory-based electrochemical analyses with field exposure tests. The population comprises commercially available nanostructured coatings formulated with different nanoparticle types, such as silica, titanium dioxide, and graphene oxide, applied onto Q235 steel panels measuring 100 mm by 100 mm. A purposive sampling technique was employed to select fifteen coating formulations, each replicated thrice, totaling forty-five samples for laboratory testing. The primary data collection instruments include electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, and surface morphology analysis via scanning electron microscopy (SEM). Additionally, field exposure was conducted in a coastal marine environment over 12 months to evaluate long-term corrosion resistance under real-world conditions. Data analysis involves statistical techniques such as analysis of variance (ANOVA) to compare corrosion rates across different nanocoatings, and regression analysis to determine relationships between microstructural features and corrosion performance. Microstructural characterization employs energy-dispersive X-ray spectroscopy (EDX) and SEM imaging, while electrochemical data are interpreted through Nyquist and Bode plots to elucidate coating effectiveness. The study is grounded in the theories of corrosion kinetics and barrier protection, notably Mott-Schottky analysis and the passivation theory, to interpret how nanostructured coatings influence electrochemical stability and corrosion inhibition mechanisms. Expected findings include statistically significant improvements in corrosion resistance in nanocoated samples over conventional coatings, evidenced by higher impedance values, lower corrosion current densities, and reduced pit formation in SEM observations. It is anticipated that coatings containing graphene oxide nanoparticles will demonstrate superior performance due to their exceptional barrier properties and chemical stability. These results are expected to contribute novel insights into the microstructural attributes that optimize protective efficacy in nanoscale coatings, thus filling existing gaps identified in prior studies regarding long-term durability and scaling effects of nanocoatings in marine settings. This research advances the body of knowledge by systematically correlating the microstructural characteristics of nanostructured coatings with their electrochemical performance in marine environments, providing a scientific basis for formulation improvements. It also refines existing corrosion theories by integrating nanoscale phenomena and barrier mechanisms within the corrosion process. The main conclusion indicates that nanostructured coatings significantly enhance corrosion resistance compared to traditional coatings, primarily through the formation of dense, defect-free microstructures and improved barrier properties. Based on these findings, the study recommends further exploration of hybrid nanocoating systems combining multiple nanoparticles to synergistically enhance protective qualities. It also suggests developing standardized protocols for field application and long-term performance monitoring in diverse marine environments. Future research should investigate environmental impacts, economic feasibility, and scalability of nanocoatings for commercial marine infrastructure, ensuring practical relevance and sustainability of these advanced protective materials.