Development and Optimization of Ti-Based Composite Coatings for Corrosion Resistance

Thesis Abstract

Corrosion significantly compromises the longevity and performance of metallic structures, especially in aggressive environments such as marine and industrial settings, underscoring the urgent need for effective protective coatings. Titanium (Ti) and its alloys are renowned for their high strength-to-weight ratio, excellent corrosion resistance, and biocompatibility; however, their application is often limited by surface-related corrosion issues under extreme conditions. This study aims to develop and optimize Ti-based composite coatings with enhanced corrosion resistance through innovative material integration and surface engineering techniques. The research specifically seeks to identify optimal composite formulations, evaluate their corrosion performance, and understand the underlying mechanisms contributing to improved durability. A mixed-methods research design comprising experimental coating fabrication and quantitative performance assessment was employed. The study population consisted of commercially available titanium substrates, with a sample size of 150 specimens prepared for coating treatments. The composite coatings were synthesized using a plasma spray technique, incorporating varied weight percentages of ceramic reinforcements such as titanium carbide (TiC), titanium boride (TiB2), and carbon nanotubes (CNTs). Parameter optimization was guided by a factorial experimental design that manipulated variables including coating thickness, reinforcement percentage, and spraying voltage. Data collection instruments included scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and confocal laser scanning microscopy for surface and phase characterization, alongside electrochemical testing methods — specifically potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) — to evaluate corrosion performance. The analytical framework involved analysis of variance (ANOVA) to determine the significance of process parameters on coating quality, regression analysis for model development, and surface roughness and corrosion data were statistically analyzed to identify optimal conditions. Additionally, the study applied the Theory of Composite Materials to interpret the influence of reinforcements on barrier properties and corrosion resistance. Principal component analysis (PCA) was employed to elucidate relationships among multiple variables and performance metrics. Expected findings include the identification of a composite formulation, likely with 20 wt% TiC and 10 wt% CNTs, that exhibits superior corrosion resistance characterized by a decrease in corrosion current density by up to 70%, enhanced impedance modulus, and improved surface integrity. SEM and EDS analyses are anticipated to reveal homogeneous dispersion of reinforcements within the titanium matrix, while XRD patterns are expected to confirm phase stability post-coating. The study is projected to demonstrate that the optimized composite coatings significantly outperform conventional Ti coatings and uncoated titanium substrates under simulated aggressive environments, such as saline solutions. This research contributes new knowledge by providing a comprehensive understanding of the role of specific ceramic reinforcements in augmenting the corrosion resistance of Ti-based coatings and by establishing a predictive model for coating performance based on process parameters. It advances the field of surface engineering by illustrating how tailored composite formulations can extend the service life of titanium components in corrosive environments. The study concludes that plasma-sprayed Ti-based composite coatings incorporating TiC and CNT reinforcements, produced under optimized parameters, offer a feasible and effective strategy for corrosion protection in industrial applications. Recommendations include the adoption of the developed coating system for marine and chemical processing equipment, further investigation into long-term durability and mechanical properties, and the exploration of environmentally friendly spraying techniques. Future research should focus on scaling the coating process for industrial deployment and investigating the synergistic effects of alternative reinforcement materials on corrosion and wear resistance.