Sodium alginate and its modified counterpart as sustainable-based corrosion inhibitors for N80 pipeline carbon steel: Experimental and theoretical approach

Sodium alginate is a highly promising biopolymer for use as an eco-friendly/green corrosion inhibitor (CI), despite its limited solubility. In this study, a green and water-soluble modified sodium alginate (MSA) salt was synthesized and employed as a CI on pipeline N80 carbon steel (N80CS) in artificial sea water (ASW) medium. Various analytical tools related to surface and structure were utilized to describe the properties of the newly synthesized MSA polymer. Along with surface analyses, the corrosion protection characteristics of MSA on N80CS substrates at various concentrations were examined using gravimetric, traditional, and sophisticated electrochemical experimentations. Tafel polarization tests revealed that MSA exhibited mixed-type CI characteristics, with a predominance of anodic inhibition. Inhibition efficiency of MSA raised with increasing concentration, attaining a maximum of 89.85 and 94.90 % at 500 and 750 ppm, respectively. The physiochemical adsorptions of MSA on the N80CS surface were verified through the Langmuir adsorption model isotherm. The corroborated adsorption of MSA on the N80CS surface through the formed inhibitor thin film to prevent metal corrosion was confirmed by the surface characterizations carried out on inhibited surfaces. The experimentally obtained results were confirmed by the theoretical investigations using the molecular dynamics and density functional theoretical aspects.