The study of aluminium sacrificial anode as an external galvanic cell in the underground cathodic protection system

Abstract

The focus of this study is to determine the effectiveness of external galvanic cell as an addition power supply in the sacrificial anode cathodic system. A unit in an external galvanic cell has a cell consisting of sacrificial Al anode, copper bars as a cathode and a solution of 3.5 wt. % NaCl as the electrolyte. A set of galvanic cell consists of a single cell, a double and a combination of series-parallel connection. The protected steel have an expose surface area of 1cm2 while the anode was scrap metal. Both anode-cathode were buried in the underground medium consisting of 70 wt. % sea mud, 10 wt. % laterite soil and 20 wt. % MgCl2. The monitoring was carried out for two weeks to observe the changes on the protection potential, Vp, cell potential, Vcell and current density for different connections. All voltage measurement was carried out using a saturated calomel electrode (SCE) as reference electrode. The analysis showed that all connections suitable for the use of cathodic protection system but the most suitable connection is four galvanic cells with combination of series and parallel connections galvanic cells because their protection potential was between -0.780 to 1.030 V versus SCE. The corrosion product is protected efficiently at higher current density.