Effect of Si Content on Microstructures and Electrochemical Properties of Al-xSi-3.5Fe Coating Alloy

• Published in: Materials Vol. 16; no. 23; p. 7407
• Main Authors: Wu, Yufeng, Shen, Ying, Wang, Qi, Liu, Yuhang, Shi, Dongming, Liu, Ya, Su, Xuping
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 28.11.2023
• Subjects: Al-xSi-3.5Fe coating alloy; Alloys; Aluminum alloys; Aluminum base alloys; Aluminum plating; Analysis; Atoms & subatomic particles; Chemical properties; Coatings; Computer animation; Computer programs; Corrosion and anti-corrosives; Corrosion resistance; Corrosion resistant alloys; Electrochemical analysis; electrochemical performance; Electrode potentials; Electrodes; Electrolytic cells; Galvanic corrosion; Hot dip aluminizing; Immersion coating; Intermetallic compounds; Iron; Low carbon steel; Mechanical properties; Metal industry; Microstructure; Morphology; Plating; Protective coatings; Qualitative research; Silicon; Software; Spectrum analysis; Technology application; Zinc; United Kingdom; China; Beijing China; United Kingdom > UK; United States > US; Germany; microstructure; Al-xSi-3.5Fe coating alloy; electrochemical performance
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma16237407

Hot-dip aluminum alloy is widely used in the engineering fields. However, during the aluminum plating process, Fe inevitably enters and reaches a saturation state, which has a significant impact on the corrosion resistance and microstructure of the coating. Currently, adding Si during the hot-dip aluminum process can effectively improve the quality of the coating and inhibit the Fe-Al reaction. To understand the effect of Si content on the microstructure and electrochemical performance of Al-xSi-3.5Fe coating alloys, the microstructure and post-corrosion morphology of the alloys were analyzed using SEM (Scanning Electron Microscope) and XRD (X-ray Diffraction). Through electrochemical tests and complete immersion corrosion experiments, the corrosion resistance of the coating alloys in 3.5 wt.% NaCl was tested and analyzed. The results show that the Al-3.5Fe coating alloy mainly comprises α-Al, Al Fe, and Al Fe. With the increase in Si addition, the iron-rich phase changes from Al Fe and Al Fe to Al Fe Si. When the Si content reaches 4 wt.%, the iron-rich phase is Al Fe Si , and the excess Si forms the eutectic Si phase with the aluminum matrix. Through SKPFM (Scanning Kelvin Probe Force Microscopy) testing, it was determined that the electrode potentials of the alloy phases Al Fe, Al Fe, Al Fe Si, Al Fe Si , and eutectic Si phase were higher than that of α-Al, acting as cathode phases to the micro-galvanic cell with the aluminum matrix, and the corrosion form of alloys was mainly galvanic corrosion. With the addition of silicon, the electrode potential of the alloy increased first and then decreased, and the corrosion resistance results were synchronous with it. When the Si content is 10 wt.%, the alloy has the lowest electrode potential and the highest electrochemical activity.