Effect of Impressed Potential on the SCC of Al-Brass

J. Ocean Eng. Technol. 2004;18(1):69-74.

Al-황동의 응력부식균열 특성에 미치는 인가전위의 영향

정해규,임우조

현대중공업,부경대학교 기계공학부

Keywords: SCC, Al-brass, Dezincification, Constant Displacement Tester, Impressed Potential

핵심용어: 응력부식균열, Al-황동, 탈아연, 일정변위형 실험장치, 인가전위

Abstract

In general, the protection method of Shell and Tube Type heat exchanger for a vessel has been applied as a sacrificial anode, which is attached at the inner side of the shell. However, this is an insufficient protection method for tube. Therefore, a more suitable method, such as the impressed current cathodic protection for tube protection, is required. Al-brass is the raw material of tubes for heat exchanger of a vessel where seawater is used for cooling the water. It has a high level of heat conductivity, excellent mechanical properties, and a high level of corrosion resistance, due to a cuprous oxide (Cu$_2$O) layer against th seawater. However, in actuality, it has been reported that Al-brass tubes for heat exchanger of a vessel can produce local corrosion, such as stress corrosion cracking (SCC). This paper studied the effect of impressed potential on the stress corrosion cracking of Al-brass for impressed current cathodic protection in 3.5% NaCl +0.1% NH$_4$OH solution, under flow by a constant displacement tester. Based on the test results, the latent time of SCC, stress corrosion crack propagation, and the dezincification phase of Al-brass are investigated.