Scale and corrosion inhibition performance of carboxymethyl chitosan

Abstract

A series of carboxymethyl chitosan (CMCS) with various degrees of carboxymethyl substitution was prepared from two chitosan samples with different molecular weights. Static scale inhibition method, scanning electron microscope (SEM), X-ray diffraction (XRD), weight-loss method, and electrochemical measurements were taken to study the effects of internal structural factors (molecular weight, degree of carboxymethyl substitution, etc.) and external environmental factors (dosage, temperature, etc.) of CMCS on the inhibition of CaCO 3 scale and the corrosion on carbon steel, respectively. The results showed that CMCS had good scale and corrosion inhibition effects. Under the similar degree of carboxymethyl substitution, the scale and corrosion inhibition efficiencies of CMCS with low molecular weight were higher than that with high molecular weight; and the higher the degree of carboxymethyl substitution was, the better scale and corrosion inhibition effects it had. SEM and XRD results indicated that the scale-inhibition mechanisms of CMCS were mainly ascribed to its notable chelation and complexation with Ca 2+ , dispersion effect on CaCO 3 microcrystal, and the distortion of the CaCO 3 lattice, which caused the formation of unstable vaterite and aragonite structures. The results of electrochemical method showed that CMCS was a kind of mixed-type corrosion inhibitors, which could inhibit both cathode and anode reactions. The corrosion inhibition mechanisms were mainly ascribed to that the active functional groups such as hydroxyl, amino and carboxyl groups of CMCS were easy to chelate with Fe to form a monolayer protective film, so as to isolate the corrosion media and achieve the purpose of corrosion inhibition for carbon steel. In short, CMCS, as a green and environmental-friendly water treatment agent, has good scale and corrosion inhibition effect, and a wide application potential.