Water-soluble chitosan salt as ecofriendly corrosion inhibitor for N80 pipeline steel in artificial sea water: Experimental and theoretical approach

Chitosan, as a proficient biopolymer, has enormous potential as an ecofriendly corrosion inhibitor (CI), but their limited solubility restricts practical applications. Herein, an eco-friendly and water-soluble chitosan salt (CS) was utilized as a green CI on N80 pipeline steel in artificial sea water. Several structural and surface analytical tools were engaged in describing the characteristics of novel CS polymer. The corrosion inhibition efficiencies of CS on steel at different concentrations were investigated through gravimetric, conventional and advanced electrochemical techniques along with the surface analyses. Tafel polarization tests specified that CS performed as mixed-type CI with prevalent anodic inhibition characteristics. At a concentration of 1000 ppm, CS provided an inhibition efficiency (IE) of 96.68 %, following physiochemical adsorptions of CS on N80 surface validated by fitting Langmuir adsorption isotherm. However, the reductions in the values of IE at high temperature specified that the CS is the temperature dependent CIs. Scanning electrochemical microscopic evaluation confirmed the formation of thin CS inhibitors films with high electrochemical stability on N80 steel in saline. The performed surface characterizations on inhibited surfaces validated the adsorption of CS on the N80 surface by forming thin inhibitor film to obstruct metal corrosion. The theoretical simulation studies using molecular dynamics and density functional theory corroborated the experimentally obtained results.