Coupling of electrochemical techniques to study copper corrosion inhibition in 0.5 mol L-1 NaCl by 1-pyrrolidine dithiocarbamate

International audienceIn this work, as for the preliminary step to the protection of Al 2xxx alloys, the anticorrosion effect of environmentally friendly 1-pyrrolidine dithiocarbamate (PDTC) on Cu was investigated by combining various electrochemical methods in addition to SEM-EDS analyses and gravimetric measurements. The Cu/PDTC system was used as a model to simulate the inhibition of Cu-rich particles contained in Al 2xxx alloys. The corrosion test solution was 0.5 mol NaCl in the presence of 10(-4), 10(-3), or 10(-2) mol L-1 PDTC. The immersion time of the copper electrode was extended generally up to 24 h. By EQCM measurements, a marked protective effect of PDTC was observed for the highest PDTC used, and corroborated by voltammetry and EIS measurements. The cathodic reduction under constant current allowed determining the corrosion products remaining on the copper surface in terms of electrical charge. The protective effect of PDTC was explained by the formation of highly stable compounds on the copper surface, which decreases the rate of both anodic dissolution and oxygen reduction reaction

Cathodic behavior of pure Al in sulfate media

International audienceThe cathodic behavior of Al in 0.5 M Na2SO4 solution was studied by electrochemical methods. It was shown that the reduction of Fe(CN)63- was difficult when an oxide layer was formed on the electrode surface during 1 h immersion in 0.5 M Na2SO4 solution due to the poor ionic and electronic conductivities of Al hydroxides. This reaction required a high cathodic overpotential on Al surface pre-treated at –2 V/SCE Al and was kinetically more difficult in comparison to platinum. Rotating disk electrode measurements showed that oxygen reduction reaction (ORR) was controlled by kinetics on both Al pre-treated at –2 V/SCE and oxidized Al cathodic dissolution was controlled by the supply of OH– ions through H2 evolution and by ORR on both oxidized Al electrode and the Al surface pre-treated at –2 V/SCE. Polarization curves obtained at different pH values showed that no dissolution behavior was observed at pH 5, whereas in neutral and alkaline solutions, OH– ions production induced chemical dissolution of the hydroxide layer. In O2 supersaturated solution, it was shown that ORR kinetics were slightly favored

XANES Studies of Chromate Replacements in Oxide Films on Aluminum

The chemistry of conversion coatings on aluminum containing chromate and non-toxic chromate replacements has been investigated using XANES. Chromate conversion coatings contain 20% 6-valent chromium which is gradually lost on immersion in a corrosive environment. The most promising alternative coatings are those based on phosphotungstate. The chemistry of these and coatings containing Mo, V, and Mn are discussed

Coupling of electrochemical, electrogravimetric and surface analysis techniques to study dithiocarbamate/bronze interactions in chloride media

International audienceInteraction between ammonium pyrrolidinedithiocarbamate (PDTC) and bronze in 30 g L-1 NaCl was investigated at several concentrations between 0.1 and 10 mM by means of various electrochemical and spectroscopic techniques. Electrochemical measurements revealed a fast adsorption process of PDTC on Cu and Pb and the formation of a thick insulating and protective film with a high surface coverage. At high concentrations, PDTC prevents oxides formation. Surface analyses confirm PDTC adsorption on bronze mainly via interaction between sulphur atoms and Cu sites to form Cu I-PDTC complex