The corrosion behaviour of nanograined metals and alloys
P. Herrasti, C. Ponce de Leon, F. C. Walsh,
Rev Metal Madrid 48, 377 (2012).
Abstract
There has been considerable interest in the properties of nanocrystalline materials over the last decade. Such materials include metals and alloys with a crystal size within the order of 1 to 100 nm. The interest arises due to the substantial differences in electrical, optical and magnetic properties and also due to their high adsorption capability and chemical reactivity compared to their larger grained counterparts. In this paper, the corrosion of nanocrystalline metals and alloys is investigated and compared to the corrosion of microcrystalline materials having a similar composition. The focus is on the corrosion of nickel, copper, cobalt and iron alloys. Key aspects of different corrosion behaviour such grain boundaries and size are identified.
Organosilanes and polypyrrole as anticorrosive treatment of aluminium 2024
A. L. Correa-Borroel, S. Gutierrez, E. Arce, R. Cabrera-Sierra, P. Herrasti,
J Appl Electrochem 39, 2385 (2009).
Abstract
This paper addresses the preparation and characterisation of anticorrosive silane- and polypyrrole-based organic coatings and combinations of the two on aluminium 2024. Layer adsorption studies of organosilanes such as propyl (C3), octyl (C8) and octadecyl (C18) trimethoxysilane and polypyrrole deposits on the aluminium electrodes reveal only limited protection. Their anticorrosive power declines when they are subject to highly corrosive environments, such as salt fog cabinets, for extended periods. The combination of both deposits yields a more protective structure that affords better protection with time. The best performance is achieved with polypyrrole deposits on silanes due to the excellent bonding between the silane adsorbed on the surface of the material and the polypyrrole film. Of the three organosilanes used, the one with the shortest chain performs best. When long-chain organosilanes are used, the polypyrrole film becomes detached due to the lesser interaction between the layers. Electrochemical impedance spectroscopy and morphological studies of the layers also show the greater adhesion and lesser deterioration of polypyrrole deposits on silane layers.
Corrosion performance of conducting polymer coatings applied on mild steel
P. Ocon, AB. Cristobal, P. Herrasti, E. Fatas,
Corros Sci 47, 649 (2005).
Abstract
Conducting polypyrrole electrodes were obtained by galvanostatic electropolymerisation on mild steel electrodes from an aqueous solution. The electrochemical response of the coated electrodes in doped and in undoped state was compared with bare mild steel electrodes. The undoped polypyrrole coated electrode offered a noticeable enhancement of protection against corrosion processes. (C) 2004 Elsevier Ltd. All rights reserved.
Effect of the polymer layers and bilayers on the corrosion behaviour of mild steel: Comparison with polymers containing Zn microparticles
P. Herrasti, FJ. Recio, P. Ocon, E. Fatas,
Prog Org Coat 54, 285 (2005).
Abstract
Electrodeposition methods have been used to obtain polypyrrole and polyaniline polymer layers, bilayers and blends of these polymers on carbon steel by passivation of the steel surface in the electrodeposition solution (oxalic acid and monomer) between -0.5 and 0.3 V versus Ag/AgCl and subsequent electrodeposition using different techniques (potentiodynamic, galvanostatic and potentiostatic). The results obtained indicate that prepassivation gives rise to adherent polymer layers with excellent corrosion resistance. Of all the bilayers obtained, the best results are yielded with those in which polyaniline is deposited as the base for the deposition of polypyrrole.The electrodeposition of Zn microparticles on the previously deposited polymer layers promotes a great improvement in the corrosion current in highly aggressive solutions such as NaCl due to the effect of Zn as an anodic corrosion inhibitor. The drop in the corrosion rate depends on the amount of Zn deposited on the polymer layer, up to a certain point after which the protective effect ceases to be observed. (c) 2005 Elsevier B.V. All rights reserved.
Electrochemical and mechanical properties of polypyrrole coatings on steel
P. Herrasti, L. Diaz, P. Ocon, A. Ibanez, E. Fatas,
Electrochim Acta 49, 3693 (2004).
Abstract
The influence of preparation method on the morphology, mechanical properties and the behaviour against corrosion of polypyrrole films was investigated. The best mechanical properties (Universal microhardness, Young's modulus and elastic recovery) have been those corresponding to a coating obtained at constant current and thermally treated at 80degreesC during 1 day. The behaviour of these films performed in a corrosion media in quiescent and no quiescent solution has demonstrated that the samples with the best mechanical properties also had as the best anticorrosive protection, especially in the case of quincest solutions. (C) 2004 Elsevier Ltd. All rights reserved.
Electroactive polymer films for stainless steel corrosion protection
P. Herrasti, P. Ocon, A. Ibanez, E. Fatas,
J Appl Electrochem 33, 533 (2003).
Abstract
Electroactive polymer films of polyaniline, poly-o-toluidine and a composite of both were deposited on stainless steel and their performance as protective coatings against corrosion was evaluated. Open circuit potential and potentiodynamic studies of the polymer-coated stainless steel in a corrosive medium showed a significant shift in the corrosion potential towards more positive values. Mechanical characteristics of the films were evaluated by means of microhardness measurements, revealing nonelastic films in all cases and low hardness values that increased from polyaniline to poly-o-toluidine to the composite. The best results were obtained in the case of the polyaniline-o-toluidine composite.
This report describes the behaviour of polypyrrole and polypyrrole/carboximethylcellulose (Ppy/CMC) prepared by different methods in order to prevent the corrosion of steel. Potentiodynamic polarization curves and open circuit potential were used to evaluate the capacity of these materials to protect the surface. The results obtained allowed to assume that Ppy/CMC is better material to prevent corrosion than polypyrrole (Ppy) and potentiostatic method better than galvanostatic to obtain the deposit. (C) 2001 Elsevier Science B.V. All rights reserved.
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