La Plata, Argentina
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Tomachuk C.R.,Brazilian National Institute of Technology | Elsner C.I.,CIDEPINT | Di Sarli A.R.,CIDEPINT | Ferraz O.B.,Brazilian National Institute of Technology
Materials Chemistry and Physics | Year: 2010

The corrosion resistance of pure zinc coatings can be improved through the application of suitable chemical passivation treatments. Hexavalent chromium compounds have widely been used to formulate conversion layers providing better anticorrosive protection as well as anchorage properties to painting systems. However, taking into account that they are produced using hazardous chemical compounds, the development of alternative and "green" technologies with equivalent protective performance is a paramount purpose of many R&D laboratories working around the world. In the present paper, the corrosion behavior of zinc coatings obtained from free-cyanide alkaline baths and later subjected to a Cr3+ based passivation treatment, with and without a sealing treatment, was studied. The experimental work involved electrochemical impedance spectroscopy measurements in 0.5 M NaCl solution, surface microstructural and morphological characterization by electronic microscopy as well as chemical analysis by EDXS. The salt spray test was also performed. The analysis and interpretation of all the data coming from this battery of tests allowed inferring that both the Cr3+ based conversion treatment + adequate sealer presented a good corrosion resistance and, therefore, they could be used as neither a polluting nor toxic alternative to the traditional chromate coatings. © 2009 Elsevier B.V. All rights reserved.

Giudice C.A.,CIDEPINT | Pereyra A.M.,National University of Costa Rica
Fire and Materials | Year: 2010

The objective of this paper is to know the fire performance of wooden panels (Pinus radiata) impregnated with silica nanoparticles added to silica/alkali colloidal solutions. Two series of impregnated panels were prepared with diverse penetrations and retentions (a) after drying/curing the impregnants at laboratory conditions until reaching constant weight and (b) after finishing this stage with prior distiller water immersion for seven days and a later air exposition for attaining moisture balance. Panels were tested in a limiting oxygen chamber and in a two-foot tunnel. Some results displayed a high fire-retardant efficiency. Copyright © 2009 John Wiley & Sons, Ltd.

Rosales B.M.,CIDEPINT | Vera R.M.,Pontifical Catholic University of Valparaíso | Hidalgo J.P.,Pontifical Catholic University of Valparaíso
Corrosion Science | Year: 2010

Copper-based statuary alloys were submitted to accelerated patina formation and degradation in well-defined laboratory conditions. Analogies and differences between these patinas and patinas developed on monuments during long-term outdoor exposure are discussed. A very simple patina growth and degradation technique is proposed to better understand the electrochemical processes involved. Patinas were analysed in many replica samples and using destructive techniques not applicable to monuments due to their historic and cultural value. The best quantitative information obtained by "in situ" open circuit potential and current density measurements demonstrated the significant contribution of these electrochemical tools to Cultural Heritage maintenance. © 2010 Elsevier Ltd.

Bellotti N.,CIDEPINT | Del Amo B.,CIDEPINT | Romagnoli R.,CIDEPINT
Progress in Organic Coatings | Year: 2012

The international trade by marine transportation has increased continuously since the 70s. The undesirable accumulation of a wide variety of marine organisms (biofouling) on ship hulls can lead to significant increased costs, principally by increased fuel consumption. On the other hand, there is a great concern about the biocides commonly used in commercial antifouling (AF) protective systems due to the high concentration encountered in coastal areas and the potential damage they could cause to marine organisms. As a consequence, the development of alternative AF coatings with new natural products as biocides inhibit is a key factor. In this approach, tara tannin (TT) is being proposed as a promising solution. It is important to note that TT is obtained from the pods of the tree avoiding its cutting down. The aim of this research was, primarily, to explore the possible application of a natural and abundant product, such as the TT, in the preparation of AF coatings. So, a TT derivative was obtained and characterized to be employed as the bioactive compound in AF coatings. Previous to the immersion in natural environments, the dissolution of TT from AF coating in artificial sea water (ASW) was studied. TT was incorporated into the coating as zinc "tannate". One of the tested coatings proved to be efficient in AF protection in natural sea water (NSW) at Mar del Plata (38°08′17″S-57°31′18″W) harbor during eight months. The addition of 2% by weight of zinc oxide to the coating extended its service life until the year. © 2012 Published by Elsevier B.V.

Journal of Adhesion Science and Technology | Year: 2013

Coatings are one of the most used protection methods for metals. Metallic coatings, such as zinc and its alloys, are used to protect steel in mild corrosive environments. In aggressive environments, on the other hand, organic coatings must be employed in the so-called duplex systems. However, the galvanized steel/organic coating adhesion is a problem and many attempts had been done to solve it with the incorporation of a chromate-based or phosphate-based interlayer. Nowadays, the use of these compounds is questioned due to their environmental impact and new adhesion promoters, like silanes, are being investigated. The aim of this paper was to study the adhesion and the anticorrosive behavior of a duplex system with a layer of glycidoxypropyltrimethoxysilane (γ-GPS) between the zinc and the coating. Polarization tests and corrosion potential measurements were done on the γ-GPS/galvanized steel to select the better anticorrosive pretreatment conditions for the application of an organic traditional paint. Dried and wet adhesion of the coating to the pretreated substrate was studied by the standard tape test. Salt spray test and electrochemical noise technique were employed to study the corrosion behavior of the duplex systems. Results showed that the films of γ-GPS formed on galvanized steel diminished the corrosion current of the metal, but they do not protect the substrate by a barrier effect. The incorporation of the pretreatment in the duplex system increased the adhesion of the paint, especially when the pretreated substrate was cured 1 h at 200 °C. © 2013 Copyright Taylor and Francis Group, LLC.

Deya M.C.,CIDEPINT | Del Amo B.,CIDEPINT | Spinelli E.,CIDEPINT | Romagnoli R.,CIDEPINT
Progress in Organic Coatings | Year: 2013

Zinc phosphate and related compounds are convenient replacements for chromates. However, more eco-compatible pigments are being investigated. The objective of this research was to develop a modified zeolitic rock which is intended to replace phosphate pigments in anticorrosive paints. The modified zeolitic rock was obtained by grinding the rock followed with ionic exchange with molybdenyl ions. This "composite" has an intelligent behavior because molybdenum compounds are leached from the zeolite particle by corrodent species. The anticorrosive properties of this zeolitic rock were studied by electrochemical techniques, employing inhibitor suspensions, and formulating anticorrosive coatings. Coatings performance was evaluated by accelerated tests (humidity chamber and salt spray) and electrochemical noise measurements (ENM). Electrochemical noise data were analyzed in the time domain. The noise resistance (Rn) was compared, as far as possible, with the polarization resistance. It was demonstrated that zinc phosphate content could be reduced to one-third with respect to the recommended value in the literature. The electrochemical noise technique allowed to differentiate the anticorrosive performance of the different coatings formulated in this research. © 2012 Elsevier B.V. All rights reserved.

Bellotti N.,CIDEPINT | Del Amo B.,CIDEPINT | Romagnoli R.,CIDEPINT
Progress in Organic Coatings | Year: 2014

It is well known that during the first minutes of the immersion of any substrate in marine environments microbial colonization takes place. This event will condition the attachment of other more complex organisms and the substrate biodeterioration with concomitant loss of its functionality. The aim of this work was to assess antifouling coatings performance at early stages of immersion, in natural and artificial sea water, observing the surface condition, by scanning electron microscope (SEM), in order to predict possible results in long time immersion tests. The use of short time tests to predict future behavior is useful to adjust formulations, reduce testing time and economics cost. In this research antifouling (AF) coatings formulated with two "quebracho" tannin derivatives were chosen to be evaluated by short and long time tests. One of this coatings possessed in a longer service life, until 10 months of exposure, and at the same time, this resulted correlated with surface analysis at early stages of immersion by SEM. © 2014 Elsevier B.V.

Deya C.,CIDEPINT | Blustein G.,CIDEPINT | Del Amo B.,CIDEPINT | Romagnoli R.,CIDEPINT
Progress in Organic Coatings | Year: 2010

The performance of different replacements for chromates was studied. The anticorrosive properties of seven phosphate-based pigments, a calcium-exchange silica and a ferrite were assessed by electrochemical techniques and formulating solvent-borne paints with epoxy and alkyd resins. Paints contained 30% by volume of anticorrosive pigment, with respect to the total pigment content. The anticorrosive performance of paints was evaluated by accelerated tests (salt spray chamber) and electrochemical essays (corrosion potential and ionic resistance). Outdoor exposure tests were carried out in an urban-industrial environment during 8 years. The anticorrosive performance of the tested paints showed that there is not a clear relationship between the laboratory tests and the outdoors exposition and that none of them, by themselves can predict the behaviour of the paint under service. However, electrochemical essays with pigments may give an orientation about pigment performance in anticorrosive paints. As a general rule, if the pigment reduces notably steel corrosion rate and generates a rather high apparent polarization resistance a good anticorrosive performance may be expected. © 2010 Elsevier B.V.

Progress in Organic Coatings | Year: 2016

Silanes have been studied as adhesion promoters between metals (aluminum, galvanized steel and steel) and paints such as polyurethanes. The objective of this work was to study γ-glycidoxypropyltrimethoxysilano (glymo) as adhesion promoter between sandblasted steel and one water-based epoxy paint formulated in the laboratory. In some cases, the silane film was doped with sodium phosphate or sodium benzoate, and in other cases, glymo or extra epoxy resin were incorporated as part of the paint formulation. The performance of the metal-glymo-paint system was studied by electrochemical noise technique and accelerated tests (salt spray cabinet and humidity chamber). Dry and wet adhesions were also determined. The results showed that the incorporation of γ-glycidoxypropyltrimethoxysilane as pretreatment or in paint formulation does not enhance paint adhesion in undamaged areas. However, when the painted area was damaged, the incorporation of silane in the paint or doped silane in the pretreatment enhances paint performance in these areas. © 2015 Elsevier B.V. All rights reserved.

Journal of Materials Engineering and Performance | Year: 2015

Traditionally, chromates and phosphates were used as pretreatments for metals to protect them from corrosion during a temporary period. Nowadays, due to their toxicity, replacements are being study. The most studied compounds are based on silanes and, among them, glicidoxypropyltrimethoxysilane, aminopropyltrimethoxysilane, and mercaptopropyltrimethoxysilane are the most important ones. The objective of this research work was to study the anticorrosive protection afforded by films of γ-mercaptopropyltrimethoxysilane deposited on SAE 1010 steel in order to select the optimum preparation conditions. The films were applied on sandblasted steel after 24 or 48 h of hydrolysis of the silane in a water/methanol solution (1.5/1, by volume) and cured for 10 min at 80 °C or for 1 h at 100 °C. In order to evaluate the characteristics of the films, Fourier transformed infrared spectroscopy was done on the films and the coated surfaces were observed by scanning electron microscopy. The anticorrosive protection afforded by the films was studied by electrochemical tests employing polarization curves (Tafel mode) in 0.5 M NaCl solution and corrosion potential measurements in NaCl 0.05 M. The best results were obtained with silane hydrolyzed for 48 h cured at 80 °C for 10 min. © 2015, ASM International.

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