Effect of Er Content on Corrosion Resistance of Zinc Coating on Surface of Heat Ventilation Air Conditioner Pipes

Er element was added into the Zn-3Al zinc coating on the surface of heat ventilation air conditioner (HVAC) pipes. The effects of Er content on the microstructure, micro-hardness and corrosion resistance of the zinc coating were investigated by microstructure observation, full immersion corrosion test and salt spray corrosion test. The results show that when the amount of Er added into zinc coating was 0.06% (mass), there were no defects such as pitting in the zinc coating, and the grain size was the smallest, showing high quality of the zinc coating. The micro-hardness of the zinc coating with Er was higher in comparison with that without Er, and with the increase of Er content, the micro-hardness of the zinc coating increased first and then decreased, the maximum micro-hardness was obtained when the amount of added Er was 0.06%. The zinc coating with Er had better corrosion resistance to full immersion corrosion and salt spray corrosion compared to the zinc coating without Er. When the amount of added Er was 0.06%, the zinc coating on the HVAC pipe had the best corrosion resistance.