Analysis on Corrosion Leakage Causes of Stainless Steel Corrugated Heat Exchanger Plate

Abstract

During the operation of plate type radiator used in a certain project, the stainless steel corrugated heat exchanger plate experienced a leakage fault. In this paper, the leakage causes of corrugated heat exchanger plate were comprehensively analyzed by means of macro morphology analysis, chemical composition analysis, metallographic microstructure examination, observation of microscopic morphology by scanning electron microscope (SEM) and X-ray energy dispersive spectroscopy (EDS). Results indicated that the roughness of the high temperature oxidation film formed on corrugated heat exchanger surface, especially the center of Newton's ring, was large. This point was also the bulge of the cold stamping groove with high density of dislocations. And this point was the protrusion of the cold stamping groove, with a higher dislocation density. During the process of long-term operation, Cl- continuously accumulated at this location, forming pitting nuclei and ultimately inducing pitting. In addition, under the effect of the cold stamping residual stresses remained in the heat exchanger substrate, the stress corrosion in local areas would also be triggered. With the increasing degree of pitting corrosion and stress corrosion, the thickness of the corrugated heat exchanger plate was gradually decreased and ultimately led to leakage. It was suggested that the source of Cl element and the formation causes of high-temperature oxide films should be investigated, then the targeted improvement measures could be developed.

Keywords

• plate heat exchanger|corrugated heat exchanger plate|pitting corrosion|newton's ring|leakage