Evaluating the performance of zinc and aluminum sacrificial anodes in artificial seawater

摘要

The cathodic protection of the metallic structure buried/immersed in the aggressive media depends on the electrochemical properties of the sacrificial anode. The objective of this work is to evaluate the performance of the sacrificial anodes i.e. aluminum and zinc alloys developed in our laboratory. The microstructural analysis of the aluminum and zinc anodes revealed the formation of pure alpha and eta phases, respectively. However, in Al few precipitates were accumulated along the grain boundaries of alpha phase whereas the typical intragranular twin bands and dendrite structure was evident in the case of Zn anode. The performance of the anode materials was evaluated according to the standard test procedure (TM0190) as recommended by NACE. The mass loss and hydrogen evolution tests were conducted to determine the current efficiency of these sacrificial anode materials in artificial seawater. The current efficiency of the aluminum and zinc anode from the mass loss measurement was measured to be 93.3 and 66.6%, respectively. The anode capacity of Al and Zn was 2784.8 and 519.36 A h kg(-1) which was high as reported earlier. However, according to the hydrogen evolution test, the current efficiency was 86.2 and 95.3% for aluminum and zinc anodes, respectively. The open circuit potential of both anodes was also shifted to more negative potential (active state) within 336 h exposure to artificial sea water. (C) 2019 Elsevier Ltd. All rights reserved.