Influence of bismuth on electrochemical behavior of sacrificial aluminum anode

Abstract

PurposeTo evaluate bismuth, which is inexpensive and non‐toxic, as a substitute for mercury, indium and gallium in Al‐5%Zn‐X sacrificial anode.Design/methodology/approachThe effect of bismuth on the electrochemical behavior of Al‐5%Zn‐Bi in the artificial sea water environment was investigated. Potentiodynamic, potentiostatic, galvanostatic, weight loss and efficiency test methods were employed. The surface of the specimens were studied by SEM and analyzed by EDAX. Image analyzer was also used.FindingsAdding 0.3‐0.5%Bi to Al‐5%Zn alloy produces considerable active sites on the anode surface and, when the corrosion process continues, the corrosion will be uniform by joining these numerous shallow pits and a high efficiency sacrificial anode will emerge.Research limitations/implicationsPreventing segregation by good casting practice or homogenization heat treatment will be helpful to prevent unpredicted localized corrosion and investigating the effect of these processes on the performance of this new alloy is helpful. Investigating the performance of this new suggested alloy in environments like soil is highly recommended.Practical implicationsOwing to the toxicity of mercury and high price of gallium and indium, bismuth, which has a much lower price and showed a good performance in the present laboratory tests, can be a good substitute for the above mentioned elements.Originality/valueThe previous lack of a systematic research on the effect of bismuth which can be a good substitute for indium and gallium, on anodic behavior of aluminum gives this paper its high value.