Adsorption and Surface Analysis of Sodium Phosphate Corrosion Inhibitor on Carbon Steel in Simulated Concrete Pore Solution

Abstract

Corrosion of steel-reinforced concrete exposed to marine environments could lead to structural catastrophic failure in service. Hence, the construction industry is seeking novel corrosion preventive methods that are effective, cheap, and non-toxic. In this regard, the inhibitive properties of sodium phosphate (Na3PO4) corrosion inhibitor have been investigated for carbon steel reinforcements in 0.6 M Cl− contaminated simulated concrete pore solution (SCPS). Different electrochemical testing has been utilized including potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and Mott‒Schottky plots to test Na3PO4 at different concentrations: 0.05, 0.1, 0.3, and 0.6 M. It was found that Na3PO4 adsorbs on the surface through a combined physicochemical adsorption process, thus creating insoluble protective ferric phosphate film (FePO4) and achieving an inhibition efficiency (IE) up to 91.7%. The formation of FePO4 was elucidated by means of Fourier-transform infrared spectroscopy (FT–IR) and X-ray photoelectron spectroscopy (XPS). Quantum chemical parameters using density functional theory (DFT) were obtained to further understand the chemical interactions at the interface. It was found that PO43− ions have a low energy gap (ΔEgap), hence facilitating their adsorption. Additionally, Mulliken population analysis showed that the oxygen atoms present in PO43− are strong nucleophiles, thus acting as adsorption sites.

Inhibitive Action of Sulfide Ions on Corrosion and Enhancing Charge‐Discharge Efficiency of Zinc and Zinc‐Indium Alloy as Anode for Alkaline Batteries

“…In addition, as seen in Figure 10, the E LUMO is mostly localized around the sulfide ion (S 2− ), indicating that S 2− can not accept electrons and form feedback bonds. The chemisorptions portion of the inhibitory process is responsible for these two quantum features, where the sharing of electrons with the metal surface occurs [71] …”

“…In today's scientific landscape, computational chemistry has emerged as a critical component in comprehending the inhibitory mechanism at the metal contact. [64] Quantum chemical properties can be utilized to evaluate corrosion inhibitors' reactivity and adsorption sites, thereby establishing a correlation between the molecular structure and the inhibition process. Various quantum chemical parameters were computed for the optimal arrangement of the sulfide ion (S 2À ) when placed in a water solvent.…”

“…The chemisorptions portion of the inhibitory process is responsible for these two quantum features, where the sharing of electrons with the metal surface occurs. [71] The electrostatic potential mapping (MEP) of the sulfide ion (S 2À ) is shown in Figure 10. The color red indicates the most negative areas, while the color blue indicates the most positive regions.…”

Corrosion Prevention of Copper in 2.0 M Sulfamic Acid Using Novel Plant Extract: Chemical, Electrochemical, and Theoretical Studies

“…Based on this information, oxygen and nitrogen atoms are the sites of the reactions within the molecules. Therefore, one of the most popular ways to present this characteristic is through Mulliken analysis . Mulliken partial charges for the various atoms of the optimized molecules under study are illustrated in Figure .…”

“…Therefore, one of the most popular ways to present this characteristic is through Mulliken analysis. 66 Mulliken partial charges for the various atoms of the optimized molecules under study are illustrated in Figure 11 . Mulliken charges can also show the locations of the inhibitor molecule binding on cell surfaces.…”