Comprehensive investigation of steel corrosion inhibition at macro/micro level by ecofriendly green corrosion inhibitor in 15% HCl medium.

HYPOTHESIS: In the present time, there is enormous need for environmentally friendly and effective corrosion inhibitor for the acidizing process. During acidization 15% hydrochloric acid is used, which causes corrosion of N80 steel. EXPERIMENTS: The present study aims at the synthesis of environmentally benign corrosion inhibitor, namely 2-amino-4-(5-hydroxy-3-methyl-1H-pyrazole-4-yl)-4H-chromene-3-carbonitrile (PCP), and corrosion inhibition evaluation for N80 steel in 15% HCl. The inhibition potential of PCP was examined by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), density functional theory (DFT), and molecular dynamics simulation (MSD). The surface morphology of N80 steel samples was characterized by atomic force microscopy (AFM), contact angle measurement, UV-vis spectroscopy, and scanning electron microscopy (SEM). FINDINGS: The EIS measurements disclosed that PCP inhibits corrosion via kinetic controlled process. PDP results confirmed that PCP is a mixed type inhibitor and reduces the corrosion process effectively at 400 mg/L concentration with 98.4% efficiency. The adsorption of PCP followed Langmuir isotherm. Surface analysis by SEM, AFM, contact angle measurement, and UV-vis spectroscopy supports PCP adsorption over the N80 steel surface. The DFT study explores the adsorption and reactive regions of the PCP molecules. The MSD reveals that the diffusion co-efficient of the corrosive species in inhibited solution is less as compared to uninhibited.

Thiosemicarbazide and thiocarbohydrazide functionalized chitosan as ecofriendly corrosion inhibitors for carbon steel in hydrochloric acid solution.

Organically functionalized chitosan macromolecules namely Chitosan-Thiosemicarbazide (CS-TS) and Chitosan-Thiocarbohydrazide (CS-TCH) were synthesized and evaluated as new corrosion inhibitors for mild steel corrosion in 1M HCl. The FTIR and 1H NMR studies confirmed the formation of the derivatives. The corrosion tests were performed using weight loss method, electrochemical measurements, surface morphology (AFM), quantum chemical investigation and molecular dynamics simulation methods. The maximum efficiency of 92% was obtained at a concentration as low as 200mgL-1. The inhibitors were found to obey Langmuir adsorption isotherm and exhibited both physical and chemical adsorption. Electrochemical impedance spectroscopy (EIS) results showed an increase in polarization resistance which supported the adsorption of inhibitors on the mild steel surface. Tafel data showed a mixed type behavior with cathodic predominance. The data of quantum chemical calculations and molecular dynamics simulation supported the experimental findings.