Corrosion Behavior of Al-Mn-RE Alloy for Air Conditioning System

The effects of RE content and cold rolling and annealing on the microstructure and corrosion resistance of Al-Mn-RE alloy were studied by means of metallographic microscope, scanning electron microscope and electrochemical workstation. The results show that the eutectic phases with different sizes and irregular shapes can be seen in Al-Mn-xRE alloys. With the addition of different RE content, the amount of eutectic silicon increases, the long strip eutectic structure fines and gradually turns into spherical or short rod-like structure. When RE content reaches 0.25% or more, the eutectic structure begins to coarsen. With the increase of RE content, the corrosion potential and pore size of Al-Mn-xRE alloys increase. The corrosion potential of Al-Mn-0.18RE alloy shows a trend of positive and negative migration first, and the corrosion current density decreases first and then increases, the maximum corrosion resistance is obtained when the RE content is 0.18%. The order of corrosion potential and pitting corrosion potential of Al-Mn-0.18RE alloy from high to low is: homogenized state> cold rolled + 325 °C annealed state> rolled state> cold rolled + 475 °C annealed state. The corrosion resistance of the Al-Mn-0.18RE alloy after rolling is lower than that of the homogenized state, but the subsequent stabilization annealing treatment at 325°C can improve the corrosion resistance.