Origin of Aragonite Scale Deposition on Carbon Steel at Ambient Circumstances

The deposition of calcium carbonate scale on a metal surface is undesirable in industrial processes. Electrochemical corrosion processes at the metal water interface can induce the deposition of calcium carbonate scale. In this paper, galvanic deposition and potentiostatic deposition methods were used to investigate the influence of electrochemical corrosion behavior of carbon steel on the deposition behavior of calcium carbonate. Results reveal that aragonite tends to deposit on carbon steel due to the disturbance of ferrous ions released from a micro galvanic corrosion cell. Once anodically released ferrous ions diffuse to the adjacent cathodic regions; they not only can decrease the interfacial oxygen concentration by preferentially consuming local dissolved oxygen but also can lower the local pH by forming iron hydroxides. Such processes build a relative low CaCO3 supersaturation environment at the metal water interface, favoring the deposition of aragonite.