Blanca M. Rosales

Comparative study of organic inhibitors of coppercorrosion

Abstract The corrosion behaviour of copper in the presence of two organic inhibitors that belongto the oxime group (salycilaldoxime (SO) and benzoinoxime (BO)) has been investigated inneutral aqueous NaCl solutions. Weight-loss measurements and electrochemical impedancespectroscopy (EIS) were applied to analyse the effect of the organic compounds on the corrosioninhibition of copper. Morphology of the copper substrate after corrosion in the presence andabsence of the inhibitors was examined using scanning electron microscopy (SEM). Fouriertransform infrared (FTIR) and X-ray photoelectron (XPS) spectroscopies were used tocharacterise the surface film. A polymeric Cu (II)-inhibitor complex that totally covered thecopper surface was identified, exhibiting strong corrosion inhibition. In the first stage, copperoxides are formed adhering to the metallic surface. The inhibitory mechanism on the Cudissolution process was related to both the chelating effect of Cu (II)ions close to the coppersurface, which avoids the action of aggressive Cl− or OH− ions in solution, and the blockingaction of the organic complex surface film.

Inhibitory action of 8-hydroxyquinoline on the copper corrosion process

The effect of 8-hydroxyquinoline (HQ) on the corrosion inhibition of copper has been investigated in neutral aqueous NaCl solutions. Weight-loss measurements and electrochemical methods (impedance spectroscopy and potentiodynamic polarisation) were applied to analyse the metal corrosion behaviour in the absence and presence of the inhibitor, which is a copper ion complexing agent. Surface analysis using XPS, FTIR, and SEM–EDX allowed us to clarify the mechanistic aspects and evaluate the relative inhibitory efficiency. It was stated that a protective film is formed on the surface by polymerisation of Cu (II)–hydroxyquinoline complexes, films that plays an essential role in the inhibition of Cu corrosion. The inhibitory mechanism on the Cu dissolution process was also related to the adsorption of the HQ molecules on the surface, avoiding the adsorption of aggressive ions in solution, such as Cl− or OH−.

A survey of Argentinean atmospheric corrosion: I—Aluminium and zinc samples

The atmospheric corrosion of aluminium and zinc samples exposed at six test sites with known ambient parameters in Argentina was investigated after different outdoor exposition periods. Corrosion damage was determined by weight-loss measurements. Both D.C. and A.C. electrochemical techniques, performed in 0.1 M Na2SO4 solution employing the exposed face of the test samples, were used to characterize the protectivenesses of the surface layers generated on the metals at different exposure times during the atmospheric corrosion process in the distinct environments. The time dependence of corrosion rates as compared with the weight-loss data as well as with information from SEM and EDAX observations of the rusts concerning the structure and morphology of surface corrosion products and the presence of pollutants.

Evaluation of the protective properties of natural and artificial patinas on copper. Part I. Patinas formed by immersion

Abstract The variable character of the ambient parameters determine different passivating properties of the corrosion products formed during outdoor exposure. Three year tests, at least, are necessary in the atmosphere where the patina should be naturally formed, to have long term information about the protectiveness it can develop, its stabilisation rate and the morphology of the attack suffered by the metal. Patinas formed in laboratory, on the contrary, can have well defined chemical composition and morphology, allowing accelerated formation through uniform attack, with controllable corrosion rate of the metal. The protective properties of the corrosion products of copper forming light blue, green, purple and brown artificial patinas and of patina naturally formed during outdoor exposure were evaluated through different characterisation techniques. Potentiokinetic polarisation, scanning electron microscopy (SEM) and EDX surface analysis were applied on the weathered metal samples. The composition of the corrosion products was determined through X ray diffraction and IR spectroscopies. Comparison of the results allowed the classification of the green patina, among the artificial and the naturally formed by outdoor exposure, as the best, from the protective properties point of view. The other 3 presented different failures, consisting of poor adherence, high porosity and exfoliation of the underlying metal.

A survey of Argentinean atmospheric corrosion : II-Copper samples

Abstract Copper samples were exposed at six sites with known ambient parameters in Argentina and the atmospheric corrosion was investigated after different outdoor exposition periods. Weight-loss measurements used to determine corrosion damage were complemented with both DC and AC electrochemical techniques, performed in 0.1 M Na2SO4 solution employing the exposed face of the test samples, in order to characterize the protectivenesses of the surface layers generated on copper in the distinct environments. While the ambient aggressiveness could be well evaluated from meteorological and pollution parameters and from weight-loss data, the product protective characteristics estimated through SEM and EDAX observations and electrochemical methods yielded valuable information to understand mechanistic aspects concerning the effects of physical properties, structure and contaminant content of surface corrosion products.

Corrosión de Aleaciones Aeronáuticas de Aluminio y sus Componentes Relacionada a la Expresión Proteica del Hongo Hormoconis resinae

Resumen Este articulo muestra que los requerimientos nutricionales de oligoelementos constituyen la fuerza impulsora de la corrosion influenciada microbiologicamente que produce Hormoconis resinae en aleaciones aeronauticas de aluminio. Se compararon perfiles proteicos de biopeliculas del hongo cultivado en turbocombustible aeronautico mediante electroforesis en geles de poliacrilamida. Se caracterizo la morfologia de ataque de las aleaciones y de sus componentes metalicos puros y el crecimiento de hifas sobre cada metal mediante microscopia electronica de barrido ambiental. Se concluyo que la corrosion estaria asociada a aleantes que actuarian como oligoelementos para el microorganismo. Palabras claves: aleaciones aeronauticas, Hormoconis resinae, expresion proteica, biopelicula Corrosion of Aeronautical Aluminium Alloys and its Components Related to the Proteic Expression of the Fungus Hormoconis resinae Abstract This article shows that the metabolic needs of oligoelements constitute the driving force of the microbiologically influenced corrosion produced by Hormoconis resinae on aeronautical aluminium alloys. Protein profiles of biofilms generated by fungal strains cultivated in aeronautical fuel were compared by electrophoresis in poliacrylamide gels. The morphology attack of alloys, its component metals and the growth of hyphae in cultures were characterized by means of environmental scanning electronic microscopy. One of the main conclusions is that corrosion would be associated to alloying elements that would act as oligoelements for the microorganism.