Modified chitosan-oligosaccharide and sodium silicate as efficient sustainable inhibitor for carbon steel against chloride-induced corrosion

The aim of this work is to study the potential of modified chitosan-oligosaccharide (MCO) and sodium silicate as sustainable corrosion inhibitor for carbon steel. MCO was synthesized firstly and then its corrosion inhibition efficiency for carbon steel in 3.5 wt% NaCl solution was explored using electrochemical measurements and weight loss methods. Test results show that MCO as a mixed type inhibitor displays good inhibition property, but the protection effect became unsatisfactory under higher temperature, longer immersion time or worse flow condition. A feasible approach that is combination with sodium silicate (SS) was applied to improve the anti-corrosion performance of MCO. The effect of immersion time, temperature and flow condition on the protection performance of MCO and MCO + SS was investigated. And the inhibition efficiency of MCO is 81.86%, 82.73% and 82.11% at 333 K, 600 rpm rotation speed and 48 h immersion time, respectively, while that of MCO + SS mixture is 96.93%, 96.36% and 98.25%. Surface observation confirms the adsorption of the investigated inhibitors on the steel surface. XPS analysis and inhibition mechanism section present further vision into the protection form of inhibitors on the steel surface. It is believed that these results are of some importance for the rational design of efficient corrosion inhibitor. (C) 2019 Published by Elsevier Ltd.