Effect of Saline Atmosphere on the Mechanical Properties of Commercial Steel Wire

The effect of saline solution on the mechanical performance of a commercially available galvanized stainless steel wire is studied in detail. Stainless steel of a grade primarily used for automotive applications is used for this study. The investigation is important, especially for considering applications where such wire is subjected to a saline environment. 3.5 pct NaCl solution which replicates seawater composition is used. The quasistatic and fatigue strengths, ductility as well as hardness, and elastic modulus are systematically characterized for the galvanized stainless steel wire pre-immersed in this saline solution. In essence, the role of surface as well as bulk conditions of a material along with the presence of corrosive media in affecting its properties is thoroughly investigated. The results show that pre-immersing the galvanized wire in saline media for a limited time duration of one day produces a protective oxide layer on the surface. This surface layer enhances the resistance of the steel wire against further corrosion. Consequently, the fatigue strength of the material, primarily depending on its surface conditions, improves. On the other hand, the cross-sectional microstructure, protected by the corrosion-resistant outer shell, remains unaffected. The quasistatic strength is also controlled by the bulk of the specimen and therefore varies only nominally. Nanoindentation on the cross-section of the wire reveals no significant changes in the hardness and elastic modulus values as well. This study highlights that optimally pre-immersing in a saline solution improves the fatigue resistance of the galvanized stainless steel wire at the expense of only nominal variations in its tensile properties, hardness, and elastic modulus.