A metallographic case study of formicary corrosion in heat exchanger copper tubes

This paper presents the results of tests for corrosion damage that occurred on the inner surface of copper tubes of a shell and tube heat exchanger. A typical image was observed for corrosion caused by the presence of organic decomposition products on the copper surface, leading to the formation of carboxylic acids. Light microscopy and SEM was used to describe the nature of the ant-nest corrosion. It has been observed that the orientation of the formed tunnels can be related to their movement along the grain boundaries. The research also focused on the important role of the surface condition caused by technological processes and non-metallic inclusions on the initiation of corrosive features.