Résumé: Abstract. This study deals with the influence of the addition of vanadium and niobium with concentrations of 1.2% and 0.14%, respectively, on the variation of the microstructure, and the tribological behavior of an AISI309 austenitic stainless steel. The studied specimens were structurally characterized by optical microscopy, scanning electron microscopy (SEM) X-ray diffraction and and differential scanning calorimetry (DSC). These samples were also subjected to a tribological study using the friction wear test. The results show that the addition of vanadium and niobium causes a precipitation of stable carbides (VC, NbC) which in turn causes a decrease of the chromium carbide precipitation rate. Tribological test results have also shown that the addition of these two elements improves the wear resistance of AISI309 austenitic stainless steel by decreasing the coefficient of friction from 0.824 to 0.554.

Résumé: Abstract The Grated Agave Americana plant (GAA), from the Algerian Eastern Coast (Annaba) was tested as a corrosion inhibitor of AISI 410 steel in 0.5M H2SO4. Stationary electrochemical techniques (Potentiodynamic polarization (PDP)) and transient (Electrochemical Impedance Spectroscopy (EIS) and the method Potential of Zero Charge (PZC)), the weight loss method (WL), scanning electron microscopy associated with X-ray Dispersive Energy Spectroscopy (SEM-EDX) and Atomic Force Microscopy (AFM) were used. The polarization curves reveal that GAA acts as a mixed inhibitor. The steel surface is positively charged. Maximum efficacy is 98.65% to 10% (v/v) after 24 h immersion at 25°C. The inhibitor adsorption on metal surface is physisorbed, and obeys the Freundlich isotherm. The inhibitory efficacy decreases with temperature increase. SEM and AFM micrographs confirm the results obtained by the WL method and the electrochemical methods. GAA is a good corrosion inhibitor of AISI 410 steel in 0.5M H2SO4. Keywords: Corrosion, Agave Americana, green inhibitor, AISI 410, 0.5M H2SO4

Résumé: The protection ability of the synthesized tetrathiafulvalene derivative namely 4,4’(5’)- [Bis-(3-pyridinemethenyl)]-3,7 dimethyltetrathiafulvalene (TTF) as corrosion inhibitor of copper in 100 ppm NaCl was investigated through electrochemical, morphological, and computational methods. The obtained potentiodynamic polarization data revealed that the TTF act as an excellent mixed type corrosion inhibitor for copper in NaCl solution reached a maximum efficiency of 99.98% at 10⁻³ M, and their adsorption obeys Langmuir adsorption isotherm. It was observed that the value of the standard adsorption free energy ΔGads0 35.53 kJ/mol, that signifying a mixed mode of adsorption. Electrochemical impedance study revealed that the TTF compound formed a thin protective film on the copper surface. The equivalent circuit was used to analyze the model of the corrosion inhibition process. Surface morphology examination by scanning electron microscopy (SEM), and atomic force microscope (AFM) confirmed the formation of a protective layer on the copper surface. Furthermore, quantum chemical calculations and molecular dynamics simulation were used to investigate the inhibition mechanism at the atomic level, the obtained results support the experimental results and confirm the excellent ability of the TTF compound to protect the copper from corrosion in NaCl medium.

Résumé: The synergistic effect of Agave Americana Extract (AAE) with KI on mild steel corrosion inhibition in 0.5 M H2SO4, was investigated by Electrochemical Impedance Spectroscopy (EIS), potentiodynamic polarization (PDP) and Potential zero Charge (PZC) methods, as well as the effect of temperature. The AAE composition and the adsorbed film were analyzed by Attenuated Total Reflection - Fourier-Transform Infrared Spectroscopy (ATR-FTIR) and Scanning Electron Microscope (SEM). Results obtained showed that the presence of Synergy increased the inhibition efficiency to 86.24%. The synergism parameter indicating a competitive adsorption. Inhibition efficiency decreased with increase in temperature from 298K to 308K but increased at relatively high temperature of 328K. The activation energy, enthalpy and entropy results indicate that the adsorption mechanism is of chemical nature.

Résumé: In the dental office, surgical instruments must be sterilized for each patient, following their contamination by saliva and blood. Repeated sterilization cycles cause corrosion. A worn out and corroded instrument may cause toxicity to the patient. The aim of our study is to improve the corrosion resistance of orthodontic pliers during sterilization using green inhibitors. The behaviour of AISI 410 stainless steel with respect to corrosion was studied in a 0.5M H2SO4, using cladodes of Opuntia ficus-indica (OFI) as a green inhibitor. Temperature effect on OFI efficacy was studied for different ranges (25, 35 and 45◦C). The study was carried out using the weight loss method, the stationary electrochemical techniques (polarization curves), the transients (electrochemical impedance spectroscopy), and the scanning electron microscopy associated with X-ray dispersive energy spectroscopy (SEM–EDX) and atomic force microscopy (AFM) observations. OFI behaves as a mixed inhibitor, with a physisorbed adsorption obeying to Langmuir isotherm and, with an efficacy ranging from 95.12 to 15% (v/v) obtained after 12 h immersion at a temperature of 25◦C. The SEM–EDX and AFM observations confirm the obtained results. In conclusion, OFI improves corrosion resistance of AISI 410 stainless steels in 0.5 M H2SO4 at 25◦C.

Résumé: The inhibitor effect of Agave Americana Extract (AAE), on mild steel corrosion in 0.5MH2SO4, was investigated by potentiodynamic polarization technique and Electrochemical Impedance Spectroscopy (EIS). The inhibitor concentration effect on the corrosion process was studied. AAE acts as a mixed type inhibitor, and the inhibition efficiency increases according to the inhibitor concentration’s increase up to 81.87% at 2000 ppm. The inhibitor adsorption process is spontaneous and follows the Langmuir isotherm, as well as its molecules are both physisorbed and chemisorbed on steel surface. The inhibitor film formation was confirmed by ATR-FTIR and SEM analyses.

Résumé: The purpose of this study is to evaluate the anti-corrosive effect of natural extract of Opuntia Ficus Indica (O.F.I) for XC52 steel in 1M H3PO4. Experimental work has been achieved by weight loss,potentiodynamic polarization and EIS measurement, as well as SEM surface characterization. Among the results obtained, we can mention an inhibitory efficiency of 90% by gravimetric method and 83.9% by electrochemical method at 10% (v/v) of O.F.I. Moreover, The O.F.I extract acts as a mixed inhibitor; however, adsorption free enthalpy indicates a physisorption. The adsorption obeys the Langmuir isotherm model.These results have been improved by SEM Micrographs.

Résumé: The adsorption and inhibitor effect of Expired Amoxicillin (E.A) on mild steel in 1NHCl was studied by weight loss, potentiodynamic polarization, Electrochemical Impedance Spectroscopy (EIS), zero charge potential method (PZC) and characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The inhibition efficacy obtained by gravimetry is 94.47% at 1800 ppm after 8 h immersion. Amoxicillin acts as a mixed inhibitor. The surface is negatively charged. E.A adsorption on mild steel surface obeys Langmuir isotherm, with a spontaneous process, the E.A molecules are physisorbed.