Navegando por Assunto "Corrosion"

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    Bioactivity of Ti6Al4V alloy with bioglass and corrosion protection by silane coating
    (CDRR Editor) Marcolin, Patricia; Frozza, Caroline Olivieri da Silva; Henriques, João Antonio Pêgas; Kunst, Sandra Raquel; Crovace, Murilo Camuri; Ely, Mariana Roesch; Vieira, Lucia; Farias, María Cristina Moré; Brandalise, Rosmary Nichele
    The Ti6Al4V alloy is usually employed as a biomaterial, however, when in use, exhibits a few drawbacks such as corrosion, caused by the release of aluminum and vanadium ions besides the bioinert behavior. Bioactive coatings offer a barrier effect and bioactivity, promoting biocompatibility and osseointegration processes. The present work aims to study the biocompatibility behavior of a bioglass-containing silane film deposited on a titanium alloy (Ti6Al4V) substrate. The effect of the surface roughness of the metallic substrate was also evaluated. Film/substrate systems were characterized as their morphological, chemical, physical, electrochemical behavior, and cell cytotoxicity and cell viability. The main results pointed out that silane films augment corrosion resistance of titanium alloy substrates. The biological results indicated a growth of osteoblast cells (MG-63), for all the test conditions. The bioglass film deposited on the ground substrate exhibits the highest cell density.
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    Corrosion performance of polypyrrole-bilayer coating on carbon steel
    (Springer Nature) Cho, Liu Yao; Guiotti, Luciano Grande; Liu, Andréa Santos
    Polypyrrole doped with phosphoric acid was electrochemically synthesized on carbon steel from acetonitrile medium, and then a coating of polypyrrole doped with a long carbon chain acid, dodecylbenzenesulfonic acid or lauric acid, was electrodeposited to form a bilayer. The more protective performance of the bilayers in relation to monolayers was explained in terms of adherence and low porous, as confirmed by scanning electron microscopy. The corrosion perfor- mance was also confirmed by electrochemical measurements of open-circuit potential, potentiodynamic polarization curves and electrochemical impedance spectroscopy in chloride solution. The polarization experiments indicated that the corrosion potential values for polypyrrole-bilayer-coated steel were shifted to the positive direction in relation to uncoated carbon steel, indicating anodic protection. Tafel plots also indicated that the anodic current densities were smaller for steel coated by polypyrrole-bilayer. In addition, the electrochemical impedance data showed that the charge transfer resistance values are associated with the resistance to electron exchange between the metal and the coating, and depend on the type of long carbon chain dopant used in the outer-layer. Thus, the suggested mechanism to explain the protection of carbon steel surfaces against corrosion was associated to the passivation and barrier effect of the polypyrrole-bilayer.