EXPERIMENTAL STUDY TO CONTROL REBAR CORROSION IN A RCC MEMBER THROUGH SACRIFICIAL ANODE CATHODIC PROTECTION METHOD

Abstract

Steel reinforcement corrosion in concrete is a complex electrochemical process. Electrochemically active areas namely anode and cathode are created on the steel surface in concrete due to various factors related to steel rebar and the surrounding environment of steel in concrete. The steel rebar undergoes dissolution (corrosion) at anodic area. The presence of cathodic site is essential to support the balancing chemical reaction although no corrosion takes place at cathode. Cathodic protection is a technique where the steel reinforcement is protected from corrosion by converting it in to a cathode through supply of electrons from an external anode. Two methods i.e. Sacrificial anode cathodic protection (SACP) method and Impressed current cathodic protection (ICCP) method are very useful cathodic protection (CP) method to control/arrest the on-going corrosion of steel in concrete structures. This report first presents a brief review of steel reinforcement corrosion in which the importance of steel reinforcement corrosion monitoring in concrete are discussed, different techniques for evaluating the state of steel rebar corrosion of RCC structures, especially half-cell potential (HCP) technique are elaborated, and various techniques involved in the repair of corrosion affected concrete structures are presented, and then the results of an experimental based demonstrative study where a corroding steel reinforcement in a concrete beam was repaired through sacrificial cathodic protection technique by attaching zinc plates to the cleaned reinforcement are presented. The progress/regression of corrosion before and after application of the protection method potential was monitored through measurement of corrosion potential. The test result observations show that the corrosion potential, after repair, moved in positive (less corrosion) direction, indicating that the protection method adopted can arrest steel rebar corrosion in RCC structures. It was concluded that the sacrificial anode based cathodic protection technique can be adopted to protect reinforcement from corrosion in structures where concrete cover is low and cannot be increased due to various reasons, and where impressed current cathodic protection technique is not suitable or uneconomical.