Alejandro Ramón Di Sarli

Effect of zinc crystals size on galvanized steel deformation and electrochemical behavior

Hot-dip galvanized steel sheets with different spangle sizes were deformed by means of rolling and tension. The change of preferential crystallographic orientation and of superficial characteristics due to the deformation was analyzed by means of both X-rays diffraction and optical and scanning electronic microscopy. A correlation between such changes and the involving deformation modes was intended to be done and the spangle size influence on these modes was studied. Coating reactivity change due to the deformation was investigated by means of quasi-steady DC electrochemical tests. The results allow to infer that, in great spangle samples, the main deformation mechanism is twinning whereas in small spangle ones, pyramidal slip systems happen as well. The increase of the reactivity with the deformation is greater in tension than in rolling and it is more important in small than in great spangle samples.

Preparation and Characterization of Silanes Films to Protect Electrogalvanized Steel

Silanes are an interesting alternative to chromate-based surface treatments for temporary protection of electrogalvanized steel. In this work, the protective behavior of 3-mercaptopropyltrimethoxysilane (MTMO), 3-aminopropyltriethoxysilane (AMEO), or 3-glycidoxypropyltrimethoxysilane (GLYMO) films applied on electrogalvanized automotive quality steel sheets has been studied. The silane coating morphology, composition, and porosity were characterized by scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), x-ray fluorescence, immersion in copper sulfate, and cyclic voltammetry. The corrosion protection was evaluated by polarization curves, electrochemical noise measurements, electrochemical impedance spectrometry, and accelerated humidity chamber tests. The results showed that the silanes protect temporarily electrogalvanized steel from corrosion. MTMO forms a relatively thick and cracked film. AMEO and GLYMO films were so thin that they could not be observed by SEM but silicon was detected by EDS. MTMO provided good temporary protection, being an alternative to replace Cr(VI) as protector of electrogalvanized steel.

Zeolites as reservoirs for Ce(III) as passivating ions in anticorrosion paints

Abstract The aim of this paper was to evaluate the performance of two different modified zeolitic minerals as anticorrosion pigments in order to reduce or eliminate zinc phosphate in paints. In the first stage, the selected minerals were characterized and modified with cerium ions to obtain the anticorrosion pigments. Their inhibitive properties were evaluated by means of electrochemical techniques (corrosion potential measurements and polarization curves) employing a steel electrode immersed in the pigments suspensions. In the second stage, solvent-borne paints, with 30% by volume of the anticorrosion pigment, with respect of the total pigment content, were formulated. The performance of the resulting paints was assessed by accelerated (salt spray and humidity chambers) and electrochemical tests (corrosion potential measurements and electrochemical impedance spectroscopy) and compared with that of a control paint with 30% by volume of zinc phosphate. Results obtained in this research suggested that zeolites can be used as carriers for passivating ions in the manufacture of anticorrosion paints with at least reduced zinc phosphate content.

Corrosion performance of steel coated with different duplex systems and exposed to salt spray and continuous immersion tests

Fil: Di Sarli, Alejandro Ramon. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico la Plata. Centro de Investigacion y Desarrollo En Tecnologia de Pinturas (i); Argentina. Provincia de Buenos Aires. Gobernacion. Comision de Investigaciones Cientificas; Argentina

Hojalata: Evaluación de su Comportamiento frente a la Corrosión en Medios Acuosos

The first deterioration steps suffered by commercially available tinplate sheets exposed to different saline solutions were studied using electrochemical and surface analysis techniques, as well as optical and electronic scanning microscopy. Their results were analyzed and interpreted utilizing models able to adequately describe the degradation of those as complex as reactive metallic interfaces. It was concluded that: 1) independently of the medium, the main degradation of the metallic surface takes place within the first 24h immersion, but then its behavior is relatively stable and reproducible; 2) except in the buffer solutions based on borax or carbonate where the scarce corrosion products provided a protective effect, in the other electrolyte medium such products were, in general, a variety of non-protective iron oxyhydroxides; and 3) these results are in agreement with the electrochemically determined corrosion rates and, therefore, with the coating useful life.

Estudio de las Propiedades Anticorrosivas del Benzoato de Hierro (III) en Pinturas Base Solvente

La accion inhibidora del benzoato de hierro en electrodos de acero SAE 1010 en contacto con una suspension acuosa fue estudiada mediante ensayos electroquimicos. Paralelamente, la eficiencia anticorrosiva de este producto incorporado a cubiertas organicas base solvente fue evaluada mediante ensayos de envejecimiento acelerado (camara de niebla salina y de humedad). La evolucion del comportamiento protector de la cubierta aplicada sobre paneles de acero pintados e inmersos en una solucion 0.5M de NaClO4 fue periodicamente monitoreada por espectroscopia de impedancia electroquimica. Los resultados obtenidos indican que las pinturas formuladas con benzoato ferrico presentan una capacidad anticorrosiva comparable a las formuladas con fosfato de cinc.