CATHODIC PROTECTION MODELING OF GALVANICALLY COUPLED HEAT-EXCHANGERS

Specialized materials requirements for different components of heat exchangers create an environment for galvanic coupling. Because the tubes, tubesheet, and shell serve different functions, they may be constructed from different metals. In such systems a simulation of the current and potential distribution is useful in making an estimate of local corrosion rates. This paper illustrates techniques for modeling cathodic protection systems. Some of the general difficulties (multiple-length scale and time-dependent polarization behavior) associated with cathodic protection modeling are addressed. Techniques for modeling the tube/tubesheet area and a simplified treatment are also considered. Results of finite-difference simulations applied to a large heat exchanger compare favorably with weight-loss and reference electrode measurements. The metals tested were iron, titanium, and Galvalume (Al-Zn).