Electrochemical performance in seawater and microstructural evolution of friction stir welded joints of dissimilar AA1050 and AZ91D

This paper presents the electrochemical performance and microstructural evolution of friction stir welded joint of dissimilar AA1050 and AZ91D in seawater, for potential applications in the transportation industry. The corrosion behavior of the dissimilar weld was compared to the corrosion behavior of the parent materials, and similar welds of each alloy. The experiments were successfully conducted with an H13 hot-working tool steel in butt-joint configuration. The results revealed the presence of intercalated microstructure in the dissimilar weld and homogenous microstructures in the similar welds. The corrosion resistance properties of the parent materials and similar welds were higher than that of the dissimilar weld sample. The dissimilar weld has a current density of 3.83×10⁻⁵ A/cm² and corrosion rate of 9.99×10⁻⁴ mm/year; and is most susceptible to corrosion, due to the galvanic coupling between the dissimilar alloys and intermetallic compounds. The similar weld of AA1050 has a current density of 1.99×10⁻⁷ A/cm² and corrosion rate of 1.44×10⁻³ mm/year, while the similar weld of AZ91D has a current density of 8.58×10⁻⁶ A/cm² and corrosion rate of 1.13×10⁻¹ mm/year.