El modelo CIELAB, las fórmulas de diferencia de color y el uso de la norma europea EN 12878 en morteros y hormigones coloreados

Embellecer las mezclas cementíceas es una alternativa que se utiliza cuando surge la necesidad de valorar la apariencia de superficies. Esta cualidad, puesta de manifiesto por su color y brillo, admite disímiles terminaciones. Las diferentes alternativas de apariencia están directamente relacionadas con los materiales elegidos y sus posibles combinaciones, con la superficie obtenida tras el contacto con los moldes o por someterla a algún tratamiento superficial, y con las condiciones del curado. Otro aspecto muy importante es cuantificar qué tan diferente es un color de otro. El objetivo del presente trabajo es definir el color comparando la fórmula de diferencia de color total CIEDE1976 con la CIEDE2000 para indicadores de diferencias o similitudes. Con ese fin se utilizó la norma Europea EN12878. El color se midió en morteros elaborados con proporciones fijas de cemento gris o blanco, agua, fíller calizo, arena y pigmento (óxidos de hierro o ftalocianinas cúpricas de distinta procedencia). Por último, se comparó el color de morteros con el de hormigones que contenían dicha matriz. Los resultados muestran la variabilidad del color en función de la procedencia de pigmentos de un mismo color y de los diferentes tipos de cemento. A la vez se cuantifica lo parecido que puede ser el color de un hormigón al de su mortero.Embellish the cementitious mixtures is an alternative that is used when the need to assess the appearance of surfaces arises. This quality, evidenced by their color and gloss, supports dissimilar endings. Different alternatives of appearance are directly related to the chosen materials and combinations thereof, with the surface obtained after contact with the molds or by subjecting it to a surface treatment, and with the curing conditions. Another very important aspect is to quantify how different is a color of another. The aim of the present work is to define the color comparing the CIEDE1976 total color difference formula with the CIEDE2000 one for indicators of differences or similarities. To this end, the European EN12878 standard was used. The color was analyzed in mortars made with fixed proportions of gray or white cement, water, filler limestone, sand and pigment (iron oxides or cupric phthalocyanine from different sources). Finally, the color of the mortars was compared with the obtained in concretes containing the same matrix. The results show color variability depending on both the origin of pigments of the same color and the different types of cement. Also how similar can be the color of a concrete and its mortar is quantified

Corrosion Resistance of Steel/Zinc with Silicate Nanoparticles/Polyurethane Paint Systems in NaCl Solution

Surface characteristics and corrosion behaviour of bare electrogalvanized steel coated with polymer/nano-silicate particles added to the electrogalvanizing bath were studied by scanning electron microscopy (SEM), energy dispersive spectrometer (EDXS) and electrochemical impedance spectroscopy (EIS). After applying a barrier polyurethane paint, the paint hardness, porosity, flexibility, colour, gloss, blistering and rusting degrees, and anticorrosive protective properties in 0.05 mol·L-1 NaCl solution were also evaluated. The results correlated well and, being demonstrative of the very slow deterioration rate of the immersed coated electrogalvanized steel, they enabled to assume that if a chemically analogous but thicker coating system was applied; it could be an acceptable alternative in real service conditions.Fil: Célia R. Tomachuk. Energy And Nuclearresearch Institute; BrasilFil: Elsner, Cecilia Ines. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Tecnología de Pinturas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones en Tecnología de Pinturas; ArgentinaFil: Di Sarli, Alejandro Ramón. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Tecnología de Pinturas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones en Tecnología de Pinturas; Argentin

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

55%Al-Zn alloy coated steel sheets pre-treated with 5% Fe (NO3)3 + 15% H3PO4 solution, coated with acrylic (AC), alkyd (AQ), vinyl (VL), solvent-based epoxy (ES) or waterborne epoxy (EA) corrosion-inhibiting primers + a barrier topcoat alkyd paint, and exposed to different media were studied. Exposure conditions included salt spray or continuous immersion in solutions containing chloride or sulphate ions. The state of the exposed samples was evaluated by visual inspections, standardized physicochemical tests and electrochemical impedance (EIS) measurements. Their results allowed inferring that: 1) under immersion conditions, the best performance was offered by the ES samples; 2) most of the painting systems performed satisfactorily during their exposure to the salt spray chamber; and 3) the correlation between them permitted to explain some problems arising in service and opened the door to extend the useful life by adjusting the painting system formulation.Fil: Di Sarli, Alejandro Ramón. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Centro de Investigación y Desarrollo En Tecnología de Pinturas (i); Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; ArgentinaFil: Elsner, Cecilia Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Centro de Investigación y Desarrollo En Tecnología de Pinturas (i); Argentina. Universidad Nacional de La Plata. Facultad de Ingenieria; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentin

Corrosion Performance of Steel Coated with Different Duplex Systems and Exposed to Salt Spray and Continuous Immersion Tests

55%Al-Zn alloy coated steel sheets pre-treated with 5% Fe (NO3)3 + 15% H3PO4 solution, coated with acrylic (AC), alkyd (AQ), vinyl (VL), solvent-based epoxy (ES) or waterborne epoxy (EA) corrosion-inhibiting primers + a barrier topcoat alkyd paint, and exposed to different media were studied. Exposure conditions included salt spray or continuous immersion in solutions containing chloride or sulphate ions. The state of the exposed samples was evaluated by visual inspections, standardized physicochemical tests and electrochemical impedance (EIS) measurements. Their results allowed inferring that: 1) under immersion conditions, the best performance was offered by the ES samples; 2) most of the painting systems performed satisfactorily during their exposure to the salt spray chamber; and 3) the correlation between them permitted to explain some problems arising in service and opened the door to extend the useful life by adjusting the painting system formulation.Centro de Investigación y Desarrollo en Tecnología de Pinturas (CIDEPINT

Pinturas históricas de la Casa Rosada

Se atribuye al Presidente Domingo F. Sarmiento que la Casa de Gobierno se pintara de color rosado, utilizando la mezcla de los colores blanco y rojo para simbolizar la unión de todos los sectores políticos de la época. En esa época, nuestro país utilizaba al máximo productos derivados del matadero tales como sangre, grasa, carne y cuero. Para proteger la mampostería y evitar la humedad se le agregaba sebo a la pintura haciéndola más oleosa y así impermeabilizar los muros. Para obtener el color rosado utilizado en el pintado de las casas en el interior del país, en el momento del apagado de la cal viva se le agregaba cierta cantidad de grasa y de sangre animal fresca. La grasa hacía las veces de plastificante e impermeabilizante en tanto que la sangre animal actuaba como pigmento de coloración y plastificante. Al llevarse a cabo la restauración y puesta en valor de la fachada Balcarce de la sede del Poder Ejecutivo Nacional, los restauradores encontraron distintas capas de pintura sobre sus paredes. Se verificó que las mismas habían sido repintadas en diversas oportunidades no obstante lo cual conservaban las capas más antiguas. Este hallazgo despertó la inquietud de constatar si en las capas más profundas se confirmaba la presencia de los materiales usados en la época de la Presidencia de Sarmiento

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

Atlas de hormigón arquitectónico: resultados preliminares de los aspectos estéticos obtenidos con moldes de madera

El hormigón arquitectónico, como cualquier otro tipo de hormigón, es un material de construcción compuesto por cemento, adiciones, arena, piedra, aditivos químicos, etc., junto con el uso de pigmentos. La característica arquitectónica de este tipo de hormigón viene dada por varios aspectos estéticos de su superficie tales como el color y la textura que proporcionan diferentes acabados. El color es la consecuencia de incorporar cemento y pigmentos. Los Sistemas o Atlas se elaboraron siguiendo diversos principios que dibujan láminas, clasifican los colores de acuerdo a su diferente luminosidad, saturación y tono. Para ello, se propone una sistematización de los conceptos de color y acabado de la superficie y de los ingredientes involucrados en su producción. El presente trabajo presenta láminas diagramadas con información resumida para desarrollar un Atlas. Se elaboraron dos grupos de morteros, cada uno de ellos con pigmento rojo, amarillo o negro. El color fue definido por el espacio de color CIELAB y su evolución fue comparada por las fórmulas de diferencias de color CIEDE1976 y CIEDE2000. El brillo también se analizó. Los resultados fueron representados en seis láminas para permitir la cuantificación y visualización de los diferentes morteros coloreados. Se observó una importante variación de color desde el día 7 hasta el día 28. La fuerte formación de depósitos de carbonato de calcio asociados a un creciente brillo fue un resultado desalentador.The architectural concrete, as any other type of concrete, is a construction material composed of cement, admixtures, sand, stone, chemical additives, etc., together with the use of pigments. The architectural characteristic of this type of concrete is provided by its surface which presents several aesthetic aspects, such as color and texture that provide different finishes. Color is the consequence of cement and pigments incorporation. Systems or Atlas were elaborated following diverse principles that sketching figures, classify colors according to their differente lightness, saturations and hues. For that, a systematization of the color-surface finish concepts and the ingredientes involved in their production is proposed. The present work presents diagrammed pichtures with information summarized to develop an Atlas. Two groups of mortars were elaborated, each group with red, yellow or black pigment. The color was defined by CIELAB color space and their evolution was compared by CIEDE1976 and CIEDE2000 color difference formulas. The gloss was analised too. Results were represented in six pictures to allow quantification and visualization of the different colored mortars. An important color variation was observed from day 7 to day 28. The strong formation of calcium carbonate deposits associated to an increasing gloss was a discouraging result

Anti-Corrosion Performance of Cr+6-Free Passivating Layers Applied on Electrogalvanized

Hexavalent chromium-based passivation treatments have been successfully used as promoters of conversion coatings for many years. Their effectiveness is without question although there are many problems with regard to their environmental suitability. Hexavalent chromium compounds are carcinogenic and toxic. These problems have lead researchers to evaluate other potential systems, with lower toxicity, to ascertain if they can replace chromates as effective passivators. Researchers have proposed several alternative passivation treatments; these are processes based on molybdates, permanganates, titanates, rare earth metal and Cr3+ (considered to be non-carcinogenic) compounds. In this work, zinc coatings obtained from free-cyanide alkaline bath and submitted to a Cr3+ based passivation treatment with different colors were studied. The corrosion behavior was studied by polarization measurements and mainly by electrochemical impedance spectroscopy in 0.6 N NaCl solution. Morphological observations on the coatings surface were also performed. The results indicate that the green-colored Cr3+ passivated coatings have a good corrosion resistance followed by yellow and blue-colored passivation respectively. They could be a less polluting alternative to the traditional chromated coatings.Centro de Investigación y Desarrollo en Tecnología de Pintura

Anti-Corrosion Performance of Cr+6-Free Passivating Layers Applied on Electrogalvanized

Hexavalent chromium-based passivation treatments have been successfully used as promoters of conversion coatings for many years. Their effectiveness is without question although there are many problems with regard to their environmental suitability. Hexavalent chromium compounds are carcinogenic and toxic. These problems have lead researchers to evaluate other potential systems, with lower toxicity, to ascertain if they can replace chromates as effective passivators. Researchers have proposed several alternative passivation treatments; these are processes based on molybdates, permanganates, titanates, rare earth metal and Cr3+ (considered to be non-carcinogenic) compounds. In this work, zinc coatings obtained from free-cyanide alkaline bath and submitted to a Cr3+ based passivation treatment with different colors were studied. The corrosion behavior was studied by polarization measurements and mainly by electrochemical impedance spectroscopy in 0.6 N NaCl solution. Morphological observations on the coatings surface were also performed. The results indicate that the green-colored Cr3+ passivated coatings have a good corrosion resistance followed by yellow and blue-colored passivation respectively. They could be a less polluting alternative to the traditional chromated coatings.Centro de Investigación y Desarrollo en Tecnología de Pintura

Characterization and Corrosion Resistence of Galvanized Steel//Passivation Compositive/Polyuethane Paint Systems

The corrosion performance of electrogalvanised steel sheets pre-treated with a Cr3+ or Cr+6-based conversion layer and then covered with polyurethane-waterborne topcoat paint has been studied. The pre-treated metallic panels were coated with one of the three tested polyurethane (PU) topcoat paints, in which the dispersion type was the formulation variable. The pigment was TiO2 (rutile) with a PVC value of 10. Before and after the immersion in 0.05 M NaCl (pH 5.70) or 0.1 M Na2SO4 (pH 6.36) solutions, replicates of the different samples were subjected to standardized tests (porosity, gloss and color, hardness, flexibility). During the immersion, blistering and rusting degrees were evaluated through periodical visual inspections, while the coated steel performance was monitored by Electrochemical Impedance Spectroscopy (EIS) measurements. Initial (dry) and final (wet) paint adhesion was also determined. EIS data were interpreted and discussed in terms of the time dependence of the electrical (paint coating) and electrochemical (steel substrate) parameters associated with interfacial processes describing the metal/paint system deterioration. According to the electrochemical properties, visual inspection a standardized tests results, it was concluded that the studied polyurethane-based polymeric films applied on pretreated electrogalvanised steel provided a very effective protection against corrosion as a result of their excellent barrier properties.Centro de Investigación y Desarrollo en Tecnología de Pinturas (CIDEPINT