Corrosion inhibition by sodium potassium tartrate-Zn~(2+) system for carbon steel in rainwater collected from roof top

摘要

A synergistic effect exists between sodium potassium tartrate (SPT) and Zn~(2+) in controlling corrosion of carbon steel immersed in rain water collected from roof top and stored in concrete tank.The formulation consisting of 50 ppm of SPT and 25 ppm of Zn~(2+) has 91% corrosion inhibition efficiency (IE).As the immersion period increases IE decreases.Polarization study reveals that SPT-Zn~(2+) system functions as a mixed inhibitor.AC impedance spectra reveal that a protective film is formed on the metal surface.FTIR spectra indicate that the protective film consists of Fe~(2+)-SPT complex and Zn(OH)_2.A formulation consisting of 50 ppm of SPT,25 ppm of Zn~(2+) and 50 ppm of a biocide,N-cetyl-N,N,N-trimethyl ammonium bromide,has 98% corrosion inhibition efficiency and 100% biocidal efficiency.