Comparative Analysis of Corrosion Resistance in Aluminum Alloys for Aerospace Applications

Thesis Abstract

The increasing reliance on aluminum alloys in aerospace applications necessitates a comprehensive understanding of their corrosion resistance to ensure safety, durability, and performance longevity. Despite the widespread utilization of various aluminum alloys such as 2024, 6061, 7075, and newer variants, there exists a notable gap in comparative data concerning their corrosion behavior under simulated aerospace operating conditions. This study aims to systematically evaluate and compare the corrosion resistance of these widely used aluminum alloys, thereby contributing to informed material selection for aerospace structures. The specific objectives include (1) to characterize the corrosion mechanisms specific to each alloy via electrochemical techniques, (2) to quantify corrosion rates through weight loss measurements, (3) to analyze surface morphology and corrosion product formation using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), and (4) to investigate the influence of alloy composition and microstructure on corrosion performance through statistical analysis. The research adopts an experimental, comparative research design grounded in the positivist paradigm, incorporating laboratory-based corrosion testing complemented by statistical analysis to establish significant differences among alloys. The population comprises four aluminum alloys (2024, 6061, 7075, and a newer aluminum-lithium alloy), with a sample size of 15 specimens per alloy, generated through random sampling to ensure representativeness. Data collection methods incorporate electrochemical impedance spectroscopy (EIS), potentiodynamic polarization tests, and salt spray tests to evaluate corrosion parameters, complemented by weight loss measurements over a 90-day exposure period in a standardized saline environment. Surface analyses are conducted using SEM and EDX to observe corrosion morphologies and identify corrosion products. To ensure validity and reliability, instruments are calibrated according to industry standards, and tests are performed in triplicate to account for variability. Data analysis involves analysis of variance (ANOVA) to determine differences in corrosion rates, regression analysis to explore relationships between alloy composition and corrosion resistance, and thematic analysis of surface characterization data. The conceptual framework integrates the classic corrosion theory with the Passivation Theory, elucidating the role of alloy microstructure and alloying elements in corrosion resistance. It is anticipated that the study will reveal significant variations in corrosion behaviors among the evaluated aluminum alloys, with certain alloys demonstrating superior resistance due to microstructural characteristics or alloying elements such as lithium or zinc. It is expected that the aluminum-lithium alloy will exhibit improved corrosion resistance compared to traditional alloys, attributable to its refined microstructure and altered electrochemical properties. The findings will underscore the importance of alloy composition and heat treatment processes in corrosion prevention and lifespan extension of aerospace components. The study contributes to the existing body of knowledge by providing a detailed comparative analysis, establishing correlations between compositional variables and corrosion performance, and advancing the understanding of corrosion mechanisms in modern aluminum alloys used in aerospace. The main conclusion emphasizes that alloy selection must consider specific operational corrosion environments, with tailored heat treatments further enhancing resistance. Based on the findings, the study recommends adopting alloy-specific protective coatings and microstructural optimization strategies to mitigate corrosion risks. It advocates for ongoing research into novel aluminum alloys with inherent corrosion resistance and encourages the development of standardized testing protocols for aerospace-grade materials. Future studies should explore long-term field testing under operational conditions and investigate the synergistic effects of corrosion inhibitors and surface modifications. Overall, this research aims to inform industry standards, guide material selection, and promote sustainable aerospace manufacturing with enhanced corrosion management strategies.