Synergistic, antagonistic and biocidal effects of amino (trimethylene phosphonic acid), polyacrylamide and Zn2+ on the inhibition of corrosion of mild steel in neutral aqueous environment

Abstract

The corrosion rates of mild steel in a neutral aqueous environment containing 60 ppm C1^‐ in the absence and presence of the sodium salt of amino (trimethylene phosphonic acid) (ATMP), polyacrylamide (PAA) and Zn²⁺ have been evaluated by the classical weight‐loss method. The formulation consisting of 50 ppm PAA and 50 ppm Zn²⁺ and also the ATMP (300 ppm) ‐ZN²⁺ (50 ppm) system shows synergistic effect while the formulation consisting of 300 ppm ATMP and 50 ppm PAA shows antagonistic effect. The formulation consisting of 300 ppm ATMP, 50 ppm Zn²⁺ and 50 ppm PAA has 98 per cent corrosion inhibition efficiency and 99.9 per cent biocidal efficiency. The mechanistic aspects of corrosion inhibition are based, in a holistic way, on the results obtained from potentiostatic polarization study, X‐ray diffraction technique, UV‐visible, FTIR and luminescence spectra. Found that the protective film consists of FE²⁺‐ATMP complex, Fe²⁺‐PAA complex and Zn(OH)₂.