Corrosion Failure Study in an Oil Cooler Heat Exchanger in Marine Diesel Engine

In this article, the failure of a heat exchanger during its operation in the marine environment has been analyzed. This heat exchanger was used for cooling the oil in a marine diesel engine. Based on the existing failure history, damages in engine components were observed after 89 hours of engine working due to the leakage of the sea water to the oil. For the objective of the failure analysis, each component was investigated under the stereo optical microscopy and the scanning electron microscopy (SEM). The diameter of pits was also recorded as 8 micrometer. Besides, the chemical composition of corrosion products on the surface and in pits was additionally analyzed with the energy dispersive X-ray spectroscopy (EDAX). Results indicated that two corrosion mechanisms were failure root causes of leakages, including the crevice corrosion and the pitting corrosion. In such situation, in the engine, the oil and the sea water in tubes of the heat exchanger mixed and decreased the oil viscosity and damaged the oil film on crankshaft bearings, and finally caused damages of the engine.