Insights into the use of two novel supramolecular compounds as corrosion inhibitors for stainless steel in a chloride environment: experimental as well as theoretical investigation

Novel supramolecular (SCPs) compounds such as: {[Ni (EIN)4(NCS)2]}, SCP1 and {[Co (EIN)4 (NCS)2]}, SCP2 have been studied using weight loss (WL) and electrochemical tests on the corrosion performance of stainless steel 304 (SS304) in 1.0 M hydrochloric acid (HCl) solution. The experimental results revealed that inhibition efficacy (eta%) rises with increasing concentrations of SCPs and reached 92.3% and 89.6% at 16 x 10-6 M, 25 degrees C, from the WL method for SCP1 and SCP2, respectively. However, by raising the temperature, eta% was reduced. Polarization measurements (PDP) showed that the SCPs molecules represent a mixed-type. The SCPs were adsorbed on a SS304 surface physically, and the Langmuir adsorption isotherm was found to govern the adsorption process. The determination of thermodynamic parameters was carried out at various temperatures. Quantum chemical calculations were calculated to prove the adsorption process of SCP components, using the molecular dynamics (MD) simulations and electron density map. The inhibition performance of SCPs for SS304 dissolution in an acidic medium was proved to be excellent through FT-IR and AFM analysis. The results obtained from all measurements exhibit a high level of agreement with each other. Novel supramolecular (SCPs) compounds such as SCP1 and SCP2 have been studied using WL, PDP and EIS tests on the corrosion performance of SS304 in 1.0 M HCl solution.

Automated summary

This study investigated the corrosion performance of stainless steel 304 (SS304) in hydrochloric acid (HCl) solution using novel supramolecular compounds (SCPs) SCP1 and SCP2. Weight loss, polarization measurements, and electrochemical impedance spectroscopy (EIS) tests were conducted. The results showed that the inhibition efficacy of SCPs increased with higher concentrations and decreased with higher temperatures. The SCPs physically adsorbed on SS304 surface and followed Langmuir adsorption isotherm. Quantum chemical calculations and FT-IR/AFM analysis proved the excellent inhibition performance of SCPs. The results from multiple measurements were highly consistent.