Comparative Analysis of Corrosion Resistance in Conventional versus Nanostructured Steel Alloys

Thesis Abstract

Corrosion remains a critical challenge in the application of steel alloys across diverse industrial sectors, including construction, automotive, and shipbuilding, where material durability directly influences safety, performance, and economic costs. Despite extensive research on corrosion mitigation, comparative assessments of the corrosion resistance between conventional microstructured steel alloys and their nanostructured counterparts are limited. This study aims to systematically evaluate and compare the corrosion resistance of conventional steel alloys with nanostructured steel alloys subjected to identical environmental conditions, thereby addressing the knowledge gap concerning the influence of microstructural refinement on corrosion behavior. The specific objectives are to characterize and quantify the corrosion resistance of both steel types through electrochemical testing, surface analysis, and mechanical property evaluation; to identify the microstructural features influencing corrosion performance; and to develop predictive models linking microstructural parameters to corrosion resistance. The research adopts a comparative, cross-sectional experimental design grounded in the corrosion science framework, guided by the Passivity Theory and Surface Energy Theory, which postulate that microstructural features influence passive film formation and stability. The study population comprises commercially produced conventional steel alloys and nanostructured steel alloys synthesized via severe plastic deformation techniques such as equal channel angular pressing (ECAP). A sample size of 60 specimens (30 per steel type) is selected through stratified random sampling to ensure representativeness. Data collection involves electrochemical tests, including potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), conducted in simulated saline and acidic environments to mimic harsh conditions. Surface morphology and composition are examined using scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS). Microstructural analysis employs transmission electron microscopy (TEM) and X-ray diffraction (XRD). Mechanical properties are assessed via hardness testing and tensile strength measurements to correlate structural features with corrosion performance. The data are analyzed using ANOVA to identify statistically significant differences in corrosion parameters between the two materials, with regression analysis employed to model the relationship between microstructural characteristics (grain size, dislocation density, grain boundary density) and corrosion resistance metrics. The findings are expected to reveal that nanostructured steels exhibit superior corrosion resistance owing to increased grain boundary area and enhanced passive film stability, demonstrated by higher polarization resistance and lower corrosion current densities. Surface analyses are anticipated to confirm the presence of more uniform, adherent passive films on nanostructured samples compared to conventional steels. This research contributes to the broader understanding of microstructure-property-performance relationships in steel alloys, providing empirical evidence that nanostructuring enhances corrosion resistance. The study elaborates on the mechanisms by which grain size refinement influences passive film formation, rupture, and repair processes, thereby informing strategies for material design and surface engineering. It is projected that the findings will motivate industrial adoption of nanostructured steels in corrosive environments, leading to longer service life and reduced maintenance costs. The study concludes by recommending further research into long-term corrosion performance under cyclic loading conditions and exploration of alloying elements tailored to optimize both mechanical strength and corrosion resistance. Additionally, it advocates for the development of scalable nanostructuring processes suitable for industrial manufacturing, as well as investigations into the environmental impacts of nanostructured steel production. Overall, this comprehensive comparison provides a foundational framework for advancing corrosion-resistant steel technologies aligned with sustainable engineering practices.