Corrosion Behavior and Electrochemical Stability of Additively Manufactured Copper-Based Alloys for Marine Applications

Abstract

The fabrication of metallic components through advanced 3D printing has created new opportunities for producing intricate geometries and complex shapes that are difficult, if not impossible, to achieve using conventional manufacturing methods. While additive manufacturing (AM) offers these advantages, industries such as the marine sector require a thorough understanding of the properties of AM-produced alloys to ensure they meet the minimum performance requirements for service. In particular, marine applications demand not only sufficient mechanical strength but also reliable corrosion resistance. This thesis focuses on a comprehensive investigation of the corrosion behavior of additively manufactured nickel–aluminum bronze (NAB) and Monel 400—two alloys widely used in marine engineering. Their corrosion performance in 3.5 wt.% NaCl solution, representing seawater, is systematically compared with that of their wrought counterparts. To achieve this, the microstructural features, crystallographic texture, and phase distribution of the alloys are first characterized using advanced analytical techniques. Subsequently, their passivity and electrochemical corrosion behavior are evaluated over different immersion periods. The findings reveal that NAB develops a relatively stable corrosion product film after approximately 40 hours of immersion. However, post-heat treatment, while necessary for achieving the desired mechanical properties and reducing susceptibility to localized corrosion, negatively impacts the alloy’s overall corrosion resistance. The results further indicate that the corrosion response of heat-treated AM NAB is primarily governed by its microstructure and remains isotropic regardless of the AM technique used. Surface condition also plays a significant role, with a moderately roughened surface providing the best corrosion resistance. In the case of AM Monel 400, chemical composition emerges as the dominant factor influencing corrosion resistance. Unlike NAB, heat treatment enhances the corrosion performance of Monel 400. Although extended immersion reduces its resistance, the performance remains satisfactory for marine service.