Microstructure and Corrosion Behavior of Sn-Zn Alloys

Area of Science:

• Materials Science
• Electrochemistry
• Corrosion Engineering

Background:

• Binary tin-zinc (Sn-Zn) alloys are utilized in various applications, necessitating an understanding of their corrosion behavior.
• The microstructure and phase constitution influence alloy performance, particularly in aggressive environments.
• Investigating Sn-Zn alloys is critical for developing materials with improved durability.

Purpose of the Study:

• To investigate the microstructure, phase constitution, and corrosion behavior of binary Sn-xZn alloys (x = 5, 9, 15 wt.%).
• To evaluate the corrosion performance of these alloys in hydrochloric acid (HCl) and sodium chloride (NaCl) solutions.
• To determine the effect of zinc content on corrosion mechanisms and product formation.

Main Methods:

• Alloy preparation via induction melting of tin (Sn) and zinc (Zn) in argon, followed by solidification into cast cylinders.
• Microstructural and phase constitution analysis of the prepared Sn-Zn alloys.
• Corrosion behavior assessment in 1 wt.% HCl and 3.5 wt.% NaCl aqueous solutions at room temperature, measuring corrosion potentials and rates.

Main Results:

• Sn-9Zn exhibited a eutectic microstructure, while Sn-5Zn and Sn-15Zn showed dendritic (Sn or Zn) and eutectic phases.
• Corrosion potentials and rates were significantly higher in HCl compared to NaCl.
• Corrosion occurred via a galvanic mechanism, with Zn-rich corrosion products forming on higher Zn alloys (Sn-9Zn, Sn-15Zn), leading to spallation.
• Corrosion rate in HCl decreased with decreasing Zn weight fraction, with Sn-5Zn showing the lowest rate.

Conclusions:

• The corrosion resistance of Sn-Zn alloys in HCl is strongly dependent on the zinc content.
• Reducing the proportion of zinc in Sn-Zn alloys considerably improves their corrosion resistance in HCl.
• The Sn-5Zn alloy offers superior corrosion resistance in HCl due to its lower zinc content and resulting corrosion product characteristics.