Browsing by Author "Vera, Rosa"

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    Corrosion inhibition of copper in chloride media by 1,5-bis(4-dithiocarboxylate-1-dodecyl-5-hydroxy-3-methylpyrazolyl)pentane
    (PERGAMON-ELSEVIER SCIENCE LTD, 2008) Vera, Rosa; Bastidas, Francisco; Villarroel, Maria; Oliva, Alfonso; Molinari, Aurora; Ramirez, Daniel; del Rio, Rodrigo
    The efficiency of 1,5-bis(4-dithiocarboxylate-1-dodecyl-5-hydroxy-3-methyl-pyrazolyl)pentane (BDTCPP) as copper corrosion inhibitor in 3.5% NaCl solutions was studied by electrochemical polarization methods (Tafel extrapolation and polarization resistance method), electrochemical impedance spectroscopy and immersion assays. Results obtained in this study reveal that BDTCPP is a good inhibitor and the potentiodynamic polarization studies clearly show that BDTCPP is a mixed-type inhibitor for copper in chloride solutions. It decreases the anodic reaction rate more strongly than the cathodic reaction rate and it renders the open circuit potential of copper more positive in 3.5% NaCl solutions. The UV analysis of the protective layer of BDTCPP after corrosion experiments shows that the inhibitor prevents copper corrosion by physisorption on the metal surface, followed by chemisorption of a protective Cu(II)-complex. This Cu(II) is generated by oxidation of the Cu(I) ion formed at the beginning of the corrosion process in the aerated solution of NaCl. (C) 2007 Elsevier Ltd. All rights reserved.
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    Effect of Chloride Ions on the Corrosion of Galvanized Steel Embedded in Concrete Prepared with Cements of Different Composition
    (2014) Roman, Javier; Vera, Rosa; Bagnara, Margarita; Carvajal, Ana M.; Aperador, William
    The behavior of galvanized steel inside concrete prepared with different types of cement is of vital importance in the latest construction mega-projects, which demand durability in environments as aggressive as sea water. This paper presents the results of a year of study on the behavior of galvanized steel rebars against the action of chloride ions. The steel bars in question were used in reinforced concrete prepared with Standard Portland cement and Pozzolanic cement at a water/cement ratio of 0.45, and then exposed to a 2.6 M NaCl solution with cycles of 4 days semi-immersion and 3 days drying at 60 degrees C. The state of the galvanized steel bars was monitored through measurement of corrosion potential and corrosion current over time. Chloride ion entry profiles were also studied. The composition and morphology of the corrosion products formed on the galvanized steel were analyzed by MEB-EDAX. Polarization curves were used to evaluate the behavior of the galvanized steel bars in alkaline solutions; these bars were taken from concrete specimens exposed to an artificial marine media. It was shown that the behavior of the galvanized steel bars varies with the composition of the cement used depending on tricalcium aluminate content and its interaction with the chloride ions. In both types of concrete the galvanized steel bar was found to be in a passive state at the end of the test period.
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    Effect of surface coatings in the corrosion of reinforced concrete in acid environments
    (2013) Vera, Rosa; Apablaza, Judith; Carvajal Guerra, Ana María; Vera, Enrique
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    Industrial Byproduct-Based Concrete Subjected to Carbonation. Electrochemical Behavior of Steel Reinforcement
    (ESG, 2012) Aperador, Willian; Vera, Rosa; Maria Carvajal, Ana
    Samples of ASTM A-706 structural steel embedded in different concretes obtained from mixtures of alkali-activated steel slag and fly ash were exposed to accelerated carbonation under controlled conditions (4% CO2, 65% RH and 25 degrees C). Concretes prepared with Ordinary Portland Cement (OPC) (Type I) and Granulated Blast Furnace Slag Cement (GBFS) were used for comparison. Analysis of the electrochemical phenomenon taking place on the surface of the steel due to CO2 transport through the concrete matrix was performed by measurements of open circuit potential (OCP) and linear polarization resistance (LPR). The steel-concrete interface was characterized using Mossbauer spectroscopy at room temperature and X-ray diffraction (XRD). The electrochemical measurements suggest passivation of the steel in the concretes prepared using mixtures of steel slag and fly ash without cement.
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    Performance of Carbon Steel and Galvanized Steel in Reinforced Concrete Structures after Accelerated Carbonation
    (ESG, 2012) Vera, Rosa; Venegas, Ricardo; Carvajal, Ana Maria; Corvo, Francisco; Perez, Tezozomoc
    The aim of this paper is to study the effects of carbonation on the electrochemical properties of carbon steel and galvanized steel, immersed into cubic prisms of concrete elaborated with Portland pozzolanic cement. Reinforced concrete specimens using these two metallic materials were exposed in a carbonation chamber. In a short time period changes in carbon steel and galvanized steel potentials and in concrete resistivity indicated an increase in carbonation of steel rebar. During the test period it was observed that zinc, instead to be in active conditions, attains lower corrosion rate than carbon steel. This behavior allows to assume the use of galvanized steel as an option to enlarge useful life of reinforced concrete structures in carbonated environments.