The Inhibition Effect of Polyethylenimine (PEI) on Pitting Corrosion of 304 Austenitic Stainless Steel in 3.5% NaCl Solution

Abstract One of the problems in the case of stainless steels is their low corrosion resistance against pitting corrosion in chloride containing environments, thereby leading to severe damage to industries. In this research, the pitting corrosion of 304 austenitic stainless steel was studied in 3.5% NaCl solution at room temperature (25˚C) by performing electrochemical measurements (containing cyclic polarization and electrochemical impedance spectroscopy) and immersion measurements. Moreover, the effect of adding different concentrations of PEI inhibitor with two mean molar masses (2000 and 60,000 g/mol) on pitting corrosion was investigated. Finally, the adsorption behavior of this inhibitor on the alloy surface was investigated by ATR-FT.IR and AFM methods. It was observed that both inhibitors prevented uniform and pitting corrosion successfully, but PEI (60,000 g/mol) had better inhibition efficiency than PEI (2000 g/mol)

Structural, Micromechanical and Tribological Analyses of Electrodeposited Nickel–Graphite Coatings with Different Fractions of Graphite Microparticles

International audienceNickel-graphite composite coatings were electrodeposited on a steel substrate from typical watts bath and with specific operating conditions for different weight fractions of graphite microparticles. The weight percentage of particles in coatings and the microstructure were studied, respectively, by atomic absorption, scanning electron microscope and X-ray diffraction. The influence of graphite fraction on roughness and microhardness were also investigated. It was found that roughness increases with the increase of particle content while microhardness decreases. The tribological response was examined against high chromium steel ball using linear reciprocating tribometer. The results indicated that the friction coefficient decreases when graphite content increases. This was ascribed to the development of tribo-layer on the wear track and transfer film on the counterface. However, it was found that the improvement of wear resistance was obtained until an optimal value of graphite concentration, which provided the best condition that promoted the tribo-layer stability and maintained the matrix integrity