Magnesium and zinc organophosphonate complexonates as scaling and corrosion inhibitors

Abstract

This work deals with the creation of multipurpose formulations based on organophosphonates (OP) for simultaneous inhibition of scaling and corrosion in water consumption systems. Comparative analysis of OP-based scaling and corrosion inhibitors of various chemical composition and structure and with formulations based on the above containing OP-based zinc and magnesium complexonates was carried out. It was found that with an increase in the number of functional groups in the reagent molecule and the length of the hydrocarbon radical connecting the aminomethylenephosphonate groups, an increase in the kinetic parameters of nucleation occurs. Accordingly, the efficiency of the reagent increases, thereby working concentration can be decreased. Under the selected experimental conditions (water composition, mg/dm3: Ca2+ – 526, Mg2+ – 426, Na+ – 1127, – 871, – 1704, Cl− – 2166; temperature – 70–90°C; material: St.3), zinc and magnesium complexonates obtained at a molar ratio of 2.5:1 (OP:Ме) were tested as scaling and corrosion inhibitors. It has been found that magnesium complexonates are not inferior to zinc complexonates in efficiency. With an increase in temperature, the corrosion rate in the presence of complexonates decreases due to the formation of a “protective film” on the metal surface. The formation of a such a film is confirmed by the results of ellipsometric studies (with a SPEL-7LED spectral LED ellipsometer) and elemental analysis (an iCAP 6300 Duo atomic emission spectrometer with inductively coupled plasma). Depending on the experimental conditions, the film is 30–400 nm thick. The composition of the “protective film” includes an iron complexonate (with a molar ratio close to 1.5:1) and magnesium hydroxide. HCO− 3 SO− 2 4. © 2022, Russian Association of Corrosion Engineers. All rights reserved.