Study on corrosion resistance of copper matrix composites reinforced by Al₂O₃ whiskers

Abstract

The corrosion behavior of copper matrix composites with different Al 2 O 3 whisker content in NaCl solution (3.6 wt%) at different temperatures was studied by electrochemical test and electron microscope. The results showed that with the increase of Al 2 O 3 whisker content, the corrosion tendency of the composites first increases and then decreases. The charge-transfer resistance (Rct) value and corrosion current density tend to decrease first and then rise slowly. The whiskers can cause huge differences in performance in different directions so that it is easy to agglomerate and entangle in the matrix, which can increase the heterogeneity of materials in copper matrix alloys, hence, the addition of whiskers will cause the increase of corrosion phenomenon. As the whisker content continues to increase, a large number of reinforcing phases will form a natural protective layer when exposed on the metal surface, which will slow down the corrosion situation. As the temperature increases, the corrosion resistance decreases first and then increases. When the temperature increases from 25°C to 50°C, the electrochemical reaction is accelerated, the free electrons between the metal atoms obtain external energy, the ion migration rate is accelerated, and the corrosion reaction is more likely to occur. When the temperature increases from 50°C to 75°C, the corrosion reaction rate is mainly controlled by the diffusion of oxygen. As the temperature increases, the solubility of oxygen decreases and the cathode reaction requires oxygen to participate, consequently, the corrosion rate decreases. For the microstructure of the corrosion specimen, corrosion mainly occurred at or around the reinforcement phase/matrix interface. Intermetallic compound particles often appear near corrosion initiation points along the reinforcement phase/matrix interface, and the corrosion behavior of composites is mainly determined by copper. Copper is used as the anode of the battery, and the corrosion products are mainly copper chloride salts.