Synergistic corrosion inhibition of environment-friendly inhibitors on the corrosion of carbon steel in soft water

• The composite demonstrated synergistic effects and exhibited mixed-type corrosion inhibition behaviour.
• The composite showed remarkable corrosion inhibition property at a relatively low dosage.
• The composite functioned more environmental-friendly compared to traditional inhibitors.
• The composite have been adsorbed on the carbon steel surface as a protective film against corrosion attack.

The synergistic effect of the combination of polyaspartic acid (PASP), polyepoxysuccinic acid (PESA), polyamino polyether methylenephosphonate (PAPEMP), sodium gluconate (Glu) and Zn2+ on carbon steel corrosion was investigated using weight loss and electrochemical measurements. The combination of PASP, PESA, PAPEMP, Glu and Zn2+ is an environment-friendly inhibitor and exhibited mixed-type inhibition behaviour. The composite efficiently inhibited corrosion on carbon steel at relatively low dosages in severely corrosive soft water media. Atomic force microscopy (AFM) images and X-ray photoelectron spectroscopic (XPS) spectra further confirmed the formation of a protective film composed of the adsorbed inhibitor molecules on the carbon steel surface against corrosion attack.