Nondestructive Monitoring of Biofouling and Corrosion of OTEC Heat Exchangers

Nondestructive monitoring of biofouling and corrosion has been performed using a recently developed technique called Electrode Impedance Spectroscopy (EIS). EIS is based on the hypothesis that biofouling and corrosion films can be characterized by observing the steady state response to a small amplitude sinusoidal perturbing potential imposed on the heat exchanger material. Three potential OTEC (open and closed cycle) candidate heat exchanger materials were investigated -- copper-nickel, titanium and aluminum alloys. Results indicate that instantaneous corrosion rates can be determined at low frequencies, changes resulting from biofouling occur at high frequencies, the occurrence of localized corrosion and multiple fouling films can be identified, and the effect of cleaning the surface of the material can be readily determined.