Some surface coatings can protect metal surfaces and reduce scale deposition. Based on that, the biomimetic material polydopamine (PDA) can form a stable coating on many material surfaces; therefore, we propose an efficient one-step electroplating method for preparing anti-scale PDA coatings with high stability. The scale deposition test showed that the deposition weight of calcium carbonate on the coating is less than that of carbon steel after immersing in a supersaturated solution of calcium carbonate for 12 h at 70 °C and 90 °C, with a coating scale-inhibition efficiency of 55.02% and 66.96%, respectively. By using molecular dynamics simulation, it was found that water adsorption layers exist near the metal’s surface, and the existence of water adsorption layers on the hydrophilic surface is the main reason for the initial deposition of calcium carbonate. The interaction energy between the PDA molecular layer and water is weaker (−5.69 eV) for the surface with the PDA coating, and there is no dense water adsorption layer on the coating, which leads to the low probability of calcium carbonate adsorption on the PDA coating surface. Therefore, PDA coating can inhibit the deposition of calcium carbonate on the surface.

Numerous studies have speculated calcium carbonate (CaCO₃) nucleation induced by pre-nucleation clusters (PNCs) aggregation. However, it is challenging for experiments to directly obtain the relationship between PNCs aggregation and nucleation. Herein, we employ molecular dynamics simulations to explore the variation during PNCs aggregation, which can describe the beginning stage of CaCO₃ nucleation induced by PNCs aggregation in supersaturated solutions. The results reveal that the formation of CaCO₃ nucleus consists of PNCs spontaneous growth, PNCs solubility equilibrium, and aggregation of PNCs inducing nucleation. The PNCs aggregation, accompanied by the variation in the configuration and stability of CaCO₃ aggregate, breaks the solubility equilibrium of PNCs and creates conditions for the formation of the more stable nucleus. Besides, the CaCO₃ nucleus with the higher coordination number and the lower hydration number form when decreasing the CaCO₃ concentration or increasing the temperature. This work not only sheds light on the formation of the CaCO₃ nucleus but also contributes to the explanation for CaCO₃ polymorphism.

This paper describes the results of heat transfer performance tests for cooling water flowing inside the corrugated tube. Based on the experimental data, a dimensionless correlation for forced convection heat transfer inside the corrugated tube is attained. Moreover, the comparative fouling experiments were carried out between a corrugated tube and its corresponding plain tube. The experimental working fluid was water solution of CaCl2 and NaHCO3 with a hardness of 800 mg/L inside tubes, and the experiments were done under the conditions of 0.38 m/s liquid velocity, temperature of 60 °C at the water tank, and the same inlet temperature of working fluid inside the tubes. The experimental results show that the corrugated tube has an advantage both in heat transfer performance and in anti-fouling ability over the plain tube.