The study on zinc sacrificial anodes as an external galvanic cell in the underground cathodic protection system

Abstract

The study additional external galvanic cell in the sacrificial anode cathodic protection system in the protection for buried steel from corrosion has been performed. The exposed area of protected steel 1cm2 and it was connected as a cathode whereas the anode materials in the cathodic protection system is a scrap metal. The distance between anode-cathode is about 14.5cm and were buried in an underground environment consist of 70% seamud mixed with 10% red soil and 20% magnesium chloride solution. In the external galvanic cell, the commercial zinc sacrificial anode acts as cell anode whereas the copper plate is a cell cathode. Each sacrificial anode cathodic protection system consists of single, double and four galvanic cells and they were connected in series, parallel and one cell was connected in a combination of series and parallel. The anode and cathode materials were submerged in an electrolyte that consist 3.5wt% sodium chloride. There were 3 parameters that have been monitored within 3 weeks of the experiment which protected voltage (Vp), cell potential (Vcell) and current density. Based on the monitoring experiment, there is only a single galvanic cell has achieved the acceptable of Vp and current density that lies in -0.950V to -1.10V and 1.1μA/cm2 to 3.2μA/cm2 respectively.