Effect of Silicon on Corrosion Behaviour of Al-Zn As A Low Voltage Sacrificial Anode for Marine Environment

A sacrificial anode is a method for material protection in the sea and coastal area. This method is widely applied in marine, subsea and ship structure. Al-Zn-In, a commercial grade of the sacrificial anode had a weakness in the possibility of stress corrosion cracking due to overprotection. This study tried to substitute indium with silicon as the alloying element with composition 0.5% and 1% wt. However, commercial grade Al ingot contained trace elements such as iron in the significant amount, which could make a β-Al₉Fe₂Si₂ as an iron-rich intermetallic phase. Therefore, this study will also examine the effect of β-Al₉Fe₂Si₂ on alloys corrosion behavior. The alloy was produced through casting process with resistance furnace. Corrosion behavior was characterized by cyclic polarization in 3.5% NaCl solution. Microstructure characterization was performed using Scanning Electron Microscope, Energy Dispersive Spectroscopy, and optical metallography. The result showed that the silicon increases the corrosion rate of Aluminum Zinc (Al-Zn) and reduced the potential protection of the alloy in high strength steel. Our research showed the corrosion took place along the interdendritic area where the β-Al₉Fe₂Si₂ intermetallic phase formed in a micro galvanic manner.