Ecologically friendly corrosion inhibitor for low alloy steels and aluminium alloys

The corrosion protective properties of environmentally friendly Ce-citrate were analyzed on AISI 4130 low alloy carbon steel and AA7075 aluminum alloy in 0.05 M NaCl solution. For this purpose different concentrations of corrosion inhibitor were analyzed in the range of 0.1-0.5 mM. Electrochemical impedance spectroscopy and potentiodynamic polarization test were used for measurements of resistance to general corrosion. Pitting potential Epit value was used for the determination of resistance to pitting corrosion. Additionally, corrosion resistance measurements and determination of pitting potential value were performed in Ce-chloride solution with the aim of comparation. SEM microscopy was used for the determination of changes on the surface of the specimens after corrosion testing. The XPS method was used for the analyses of the formed inhibitory layer on the steel specimen surface. It has been shown that significant amounts of cerium, as well as the citrate anions, are present in the inhibitory layer. Ce-citrates have proved to be an effective corrosion inhibitor for AISI 4130 steel as well as an effective pitting corrosion inhibitor for AA7075 aluminum alloy. The mechanism of action of Ce-citrate on AISI 4130 steel and AA7075 aluminum alloy has been proposed.XXIII YUCORR International Conference, 116th-19th May 2022, Divčibare, Serbia, invited talk (Bojana Radojković

Zeleni inhibitori korozije sa cisteinom i kompleksom cerijum-cisteina na 7000 seriji aluminijumske legure

The aim of this study was to investigate environmentally-friendly corrosion inhibitors based on the cerium-cysteine and their effect on 7xxx series aluminum alloy. The cysteine and cerium-cysteine complex structures were analyzed by Fourier-Transform Infrared spectroscopy (FTIR). The structure of cerium-cysteine was additionally determined using Nuclear Magnetic Resonance (NMR) and Elemental Analysis. Inhibitors efficiency was analyzed with Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic polarization techniques in 0.1M NaCl at room temperature, while Scanning Electron Microscopy analyzed the surface appearance and microstructure of the tested aluminum alloy with Energy Dispersive Spectroscopy (SEM / EDS) and Optical Microscope (OM). Different amounts of cysteine were examined in order to find an optimal concentration of inhibitor. The adsorption of the inhibitors followed the Langmuir isotherm, and based on the EIS results and calculated thermodynamic potential (Gibbs free energy), cysteine and cerium-cysteine proved to be good inhibitors for tested aluminum alloy. The optimal cysteine concentration of 0.06 mM as a corrosion inhibitor of 7xxx series aluminum alloy was determined. EIS diagrams confirmed that cysteine showed better inhibition than Ce-Cys complex

Ce-citrate as green corrosion inhibitor for low alloy steel and aluminium alloys

The efficacy of the environmentally friendly corrosion inhibitor Ce-citrate (0.1-0.5 mM) was analyzed on AISI 4130 low alloy carbon steel and AA7075 aluminum alloy in 0.05 M NaCl solution. Measurements of resistance to general corrosion were performed by electrochemical impedance spectroscopy and potentiodynamic polarization test. Resistance to pitting corrosion is determined based on the value of pitting potential Epit. For comparison, corrosion resistance measurements and pitting potential determination, for considered alloys, were performed in Ce-chloride solution. Changes on the surface of the specimens after corrosion testing were analyzed by SEM microscopy. The XPS method was used for the analyses of the formed inhibitory layer on the steel specimen surface. It has been shown that significant amounts of cerium, as well as the citrate anions, are present in the inhibitory layer. Ce-citrates have proved to be an effective corrosion inhibitor for AISI 4130 steel as well as an effective pitting corrosion inhibitor for AA7075 aluminum alloy. The mechanism of action of Ce-citrate on AISI 4130 steel and AA7075 aluminum alloy has been proposed.Invited lecture (Bojana Radojković) - International conference „Recent trends in material science“, Arasu College of Arts and Science for Women, Karur, India, 18th March 2022, online

Cysteine and cerium as green corrosion inhibitors for AA7049: Mixture vs. complexation

In this work new green corrosion inhibitors based on the synthesized cerium-cysteine complex on AA7049 aluminum alloy were analyzed and compared to the mixture of CeCl3 and cysteine in 0.1 M NaCl. The complex structures were confirmed by FTIR, NMR and Elemental Analysis. It was shown that cerium was present in two oxidation states, CeIII and CeIV, when the mixture was analyzed, while there was only a CeIV oxidation state in the cerium-cysteine complex. The mechanisms of inhibitory action of the joint effect of CeCl3 and cysteine vs. their complex were proposed and analyzed in more detail

Synergistic effect of Neodymium and Cysteine as inhibitors for AA7075 alloy in NaCl solution

The synergistic effect of neodymium chloride and cysteine in NaCl solution was investigated. The concentration ratio of these two inhibitors was 1:3 (neodymium: cysteine). The corrosion resistance of AA7075 alloy was tested electrochemically using electrochemical impedance spectroscopy (EIS). Significantly higher polarization resistance in inhibitor-containing solution, along with phase angle peak shift to more negative values, indicate good corrosion inhibition by Nd-cysteine. The morphology, analyzed by scanning electron microscopy (SEM/EDS), showed that the surface of the AA7075 alloy was wholly protected from corrosion after 24h in NaCl solution

Non‑Destructive Evaluation of the AISI 304 Stainless Steel Susceptibility to Intergranular Corrosion by Electrical Conductivity Measurements

This paper examined the degree of sensitization (DOS) to intergranular corrosion (IGC) and the level of electrical conductivity of the welded and non-welded AISI 304 stainless steel to obtain a suitable correlation. The DOS was determined by the double loop electrochemical potentiokinetic reactivation method (DL EPR), while the level of electrical conductivity was measured using a commercial device (non-destructive method). After electrochemical etching in oxalic acid, the microstructure of the specimen surface was analyzed by scanning electron microscopy (SEM). At DOS greater than ~ 0.5%, a clear linear dependence between the electrical conductivity and the value of the DOS was obtained, while there was a higher deviation from linearity for lower DOS values. The mentioned correlations were discussed in the sense of the precipitation kinetics of the Cr-carbide and the formation of Cr-depleted areas of different levels near the grain boundaries. Cr-depleted areas during anodic polarization measurements show lower resistance to pit formation. The presence of Cr-depleted areas in the vicinity of grain boundaries and the reduction of carbon content in the austenite crystal lattice increases the electrical conductivity of the stainless steel