Experimental study on the relationship between metal ions and formation of CaCO3 crystalline fouling under boiling scaling system.

The effect of the addition of different concentrations of Cu2+, Fe2+, and Fe3+ on the micromorphology and crystalline structure of CaCO3 fouling was studied using the VHX-500FE digital microscope and X-ray diffraction. Results indicate that the fouling morphology becomes stubby and forms a cluster and the fouling color deepens with the increase in the concentration of metal ions. Furthermore, the relative content of aragonite increases and that of calcite decreases. Fe2+ plays a more important role in the inhibition of calcite than Fe3+ when scaling occurs in the boiling system under the condition of atmospheric environment. The reason may be that O2 participates in the inhibition process. Fe2+ and Fe3+ promote atomic transition and crystal defects, and this condition changes the absorption wavelength of fouling. Carbon steel and copper samples were immersed in test solution for 28 h as a comparative experiment. This experiment indicates that corrosion may release metal ions, which further affect the fouling morphology and phase component content in the long-term fouling process. In conclusion, fouling weight method for measuring anti-fouling property can only be used to compare materials with similar anti-corrosion property. [ABSTRACT FROM AUTHOR]