Synthesis And Study Of The Polyether Terpolymer AA-APEm-H₃PO₃ As Scale And Corrosion Inhibitor

The main problems of water cooling systems are scaling phenomenon and corrosion, which have a great impact on economy and technology. Calcium carbonate and calcium sulfate are considered most frequent among the commonly occurring scales with the use of water for cooling purposes. Corrosion, within plants and in reservoirs or on heat transfer surfaces, widely occurs in numerous industrial processes when kinds of equipments and facilities are mainly made of carbon steels and stainless steels in cooling water systems.A novel low-phosphorus terpolymer, used as scale, corrosion inhibitor, and dispersant for iron oxide, was prepared through free-radical polymerization reaction of acrylic acid (AA), oxalic acid-allypolyethoxy carboxylate (APEM), and phosphorous acid (H3PO3) in water with redox system of hypophosphorous. Structure of the synthesized AA-APEM-H3PO3 terpolymer was characterized by Fourier transform infrared spectrometer (FT-IR)、1H-NMR and TGA. The polymer possesses excellent scale inhibition performance for CaCO3 and CaSO4, outstanding ability to disperse ferric oxide, and good corrosion inhibition properties. The study showed that AA-APEM-H3PO3 exhibited excellent ability to control calcium carbonate scale, with approximately 80.97% CaCO3 inhibition and 93.94% CaSO4 inhibition at levels of 18 and 8 mg/L AA-APEM-H3PO3, respectively. The data of the light transmittance showed that, compared to hydrolyzed polymaleic acid and polyepoxysuccinic acid, AA-APEM-H3PO3 had superior ability to control iron ions scaling. The light transmittance of the solution was about 12.2% in the presence of the terpolymer when the dosage was 8 mg/L. Moreover, the corrosion inhibition efficiency could reach up to 87.14% at a dosage of 70 mg/L, with ethylene diamine tetra methylene phosphonic acid just 80.5%. Scanning electronic microscopy (SEM), transmission electron microscope (TEM), and X-ray powder diffraction (XRD) analysis were used to investigate the effect of AA-APEM-H3PO3 on morphology of calcium carbonate and calcium sulfate scales. The low-phosphorous terpolymer has also been proven to be effective inhibitor of calcium carbonate even at increasing solution temperature, pH, and Ca2+ concentration. The proposed inhibition mechanism suggests the surface complexation and chelation between the functional groups -P(O) (OH)2,-COOH and Ca2+, with polyethylene glycol segments increasing its solubility in water.