Rule of Lignosulfonate as a corrosion inhibitor for steel in neutral media, computational and reaction pathway

This study aimed to look at how lignin sulfonate (LS) inhibited corrosion of mild steel (MS) in a 1.0 M NaCl solution. Gravimetric and Electrochemical techniques were used to acquire a thorough grasp of the inhibitory effects of LS on MS corrosion. In addition, the current work used computational approaches to investigate, this connection that exists between the inhibitor compounds' functional features and their adsorption capabilities on the MS surface. Weight loss, Potentiodynamic polarization (PDP), and open-circuit studies demonstrated moderate anticorrosion properties of the investigated chemicals. Results showed that LS had the best inhibition performance, reaching 51.6% at a concentration of 0.02×10−2MLS. The polarization approach (PDP) revealed that the intended substances were mixed-type inhibitors, which prevented concurrent processes involving anodes and cathodes. In addition, the interaction pattern between the LS and MS surfaces matched, with physical interactions aiding the adsorption mechanisms of both chemicals. Furthermore, the stability of LS under several operating conditions temperature influence and submerge duration on inhibitory effectiveness were investigated. Additionally, the data fit well with both the Langmuir and El-Awady adsorption models. Molecular Dynamics (MD) and Density Functional Theory (DFT) investigations agree with those obtained through experimental methods, confirming the anticorrosion activity of the LS under investigation. Gibbs free energy value (≤−26 kJmol-1) confirms spontaneity and mainly the physical nature of the adsorption, also the mechanism of inhibition is discussed. Surface morphology indicates the formation of the LS barrier on MS.