The Study of Corrosion Behavior of Aluminum Heat Exchange Tubes in a NH_3 Condenser

摘要

This case study was performed to shed light on the corrosion mechanism of aluminum heat exchange tubes of a condenser, used for condensing NH_3 vapor. To understand the corrosion cause and mechanism, many supporting tests were carried out. The corrosion of aluminum heat exchange tubes was observed by using scanning electron microscopy (SEM). The chemical compositions of corrosion products were measured by energy dispersive spectrometer (EDS). Spark and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) were used to clarify whether the proper material was applied. The corrosivity of cooling solution was also evaluated by ICP-AES. Potentiodynamic polarization test was conducted to verify whether the inhibitors added in the cooling solution work or not. The damage of the heat exchange tubes can be attributed to the deposition of rust originating from the corroded shell and bottom plate of the condenser (made of carbon steel) on the surface of aluminum heat exchange tubes, resulting in the occurrence of crevice corrosion or so-called deposit corrosion. In addition, the presence of chloride ion (Cl~-) in the cooling solution has further accelerated the attack to the aluminum heat exchange tubes.