Relationship between corrosion product and fouling growth on mild steel, copper and brass surface

Abstract

The corrosion and fouling, accumulating on the heating transfer surface of the water supply system and the steam turbine system, are two main concerns in condenser tube maintenance. This work studied the coupling mechanism of the corrosion products and fouling on different materials, as well as the crystal forms of fouling products under diverse working conditions. The common materials of condenser tube, mild steel, brass and copper, and they were firstly pre-oxidized in different dissolved oxygen concentrations and temperatures in the reaction kettle. Then fouling experiment was performed on the corroding specimens. Consequently, at 40℃, specimens have the highest oxidation corrosion rate and the corrosion rate in turn are mild steel 2.472 mm·year−1, copper 0.789 mm·year−1 and brass 0.147 mm·year−1 at the same temperature. Slightly corroded surface is prone to foul while fouling growth rate on brass and copper surface decreases with time. Moreover, the crystal form of fouling on different surfaces are distinct. The surface free energy of mild steel, brass and copper are 55.262 mN·m−1, 33.126 mN·m−1 and 46.954 mN·m−1, respectively. Thus, specimen surface shows hydrophobicity and the adhesion probability of calcium carbonate fouling on brass, copper and mild steel surfaces increases in turn correspondingly. Calcite is the main crystal structure on mild steel, copper and brass surface after dissolved oxygen corrosion. Contrastively, aragonite only show in large numbers on corroded mild steel surface. Thus, this work provides evidence that fouling growth rate is influenced by the dissolved oxygen corrosion in the fields of heat transfer.