Experimental Study on the Design Criteria of Sacrificial Anode Cathodic Protection

Abstract

Corrosion may cause a serious deterioration on the steel structures

thus, corrosion protection is an important issue to maintain structures’ integrity. Various corrosion protection methods have been applied to solve the corrosion of the steel structures. Thermal spray coating with aluminum and zinc and cathodic protection (CP) are the most frequently used methods. Specifically, CP has been used over several decades, and it becomes a proven technology. CP can be divided into two categories, which are sacrificial anode CP (SACP) and impressed current CP (ICCP). Especially, for marine structures, SACP is beneficial to use maintenance free because it requires not only small capital expenditure (CAPEX) and operational expenditure (OPEX) but also less maintenance and monitoring than ICCP. In addition, external power source are unnecessary, and there is no over protection in the SACP system.

In this study, experiment has been performed for the structure to present the relationship between sizes and weight of sacrificial anode and current density generations. Following results are obtained from experiments.

1. There are significant difference between the used anode weights in the structures located in South Korea and CP standards, current density and anode weight standards.

2. As the surface area of the sacrificial anode increases approximately two times, a consumption rate of the sacrificial anode also approximately increases two times.

3. It is confirmed that even if required current in the structure is smaller than the generated current by the sacrificial anode, the structures are well protected by the anode.

4. In case of the CP design, an anode weight is more important than required current in the structure. In other words, entire structure is cathodically protected when weight of the sacrificial anode is satisfied with CP design criteria even if required current in the structure is lower than generated current.

Therefore, it is economically beneficial to revise the design criteria of SACP system properly according to environmental conditions and type of structures.