Improving the localized corrosion resistance of 304 stainless steel in HCl solution by adsorption of molybdate ions: Interaction mechanisms at the interface using molecular dynamics simulation and electrochemical noise analysis

The present study aimed to investigate the effect of molybdate ions to modify the 304 Austenitic Stainless Steel (ASS) surface against localized corrosion in hydrochloric acid medium. In this regard, surface characterization, such as Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS) coupled with Electrochemical Noise (EN) measurements, were conducted. Furthermore, molecular simulations were used to study the interactions of molybdate ions in the steel and solution interface. EN analysis showed that by adding 0.10 mM molybdate ions to 0.5 M HCl solution, the current and potential oscillations were drastically reduced compared to the molybdate ion-free medium, and the value of noise resistance has increased from ⁓3–8 kΩ cm2. SEM observations, XPS analysis, as well as Molecular Dynamic (MD) results showed a considerable reduction in localized corrosion owing to the formation of molybdenum-contained compounds, which were chemically absorbed on the passive film and placed at 4.533 Å over the metal surface. Although 304 ASSs are inhibited by various inhibitors, molybdate ions are efficient species for inhibition of the surface against both general and localized corrosion. Investigation of what happens on the 304 ASS surface from both macroscopic and microscopic points of view through electrochemical measurements and molecular simulations is the focus of this work.