Browsing by Keyword "Corrosion protection"
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Item Anodic films containing polyaniline and nanoparticles for corrosion protection of AA2024T3 aluminium alloy(2009-02-25) Zubillaga, O.; Cano, F. J.; Azkarate, I.; Molchan, I. S.; Thompson, G. E.; Skeldon, P.; SISTEMAS FOTOVOLTAICOS; SG; Tecnalia Research & InnovationAnodic alumina films containing polyaniline and either TiO2 or ZrO2 nanoparticles were electrochemically synthesised on an AA2024T3 aluminium alloy by a single step anodising procedure in an oxalic acid electrolyte. The morphology and composition of the films were examined by SEM, TEM, GDOES and XPS. The resultant coatings, of thickness about 2.2 μm, displayed a nanoparticle-rich layer in the near surface-regions, of thickness in the range 100-250 nm. Potentiodynamic polarisation behaviour revealed that the polyaniline and TiO2-containing films on the AA2024T3 aluminium alloy show a passive current density two orders of magnitude lower than for films with ZrO2 nanoparticles and films without nanoparticles. The coatings with TiO2 nanoparticles, but without polyaniline, showed intermediate behaviour, with a passive current density one order of magnitude lower than the coatings with polyaniline and TiO2 nanoparticles. The improved barrier protection offered by the TiO2 nanoparticle containing coatings is attributed to the presence of the nanoparticle-rich layer formed on the outer part of the coating that blocks access to the pores of the anodic alumina film.Item Chromium-free conversion coatings based on inorganic salts(Zr/Ti/Mn/Mo) for aluminum alloys used in aircraft applications(2015-08-01) Santa Coloma, Patricia; Izagirre, Usoa; Belaustegui, Yolanda; Jorcin, J.B.; Cano, F.J.; Lapeña, N.; Belaustegi, Y.; Tecnalia Research & Innovation; INGENIERÍA DE SUPERFICIES; VALORIZACIÓN DE RESIDUOS; MATERIALES PARA CONDICIONES EXTREMAS; SGNovel chromium-free conversion coatings based on Zr/Ti/Mn/Mo compounds were developed at a pilot scale to improve the corrosion resistance of the AA2024-T3 and AA7075-T6 aluminum alloys for aircraft applications. The influence of the presence of Zr and Ti in the Zr/Ti/Mn/Mo conversion bath's formulation on the corrosion resistance of the coated alloys was investigated. The corrosion resistance provided by the conversion coatings was evaluated by salt spray exposure and potentiodynamic sweeps. Optical and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS) and atomic force microscopy (AFM) operating in the Kelvin Probe mode (SKPFM) were used to provide microstructural information of the coated samples that achieved the best results in the corrosion tests. The salt spray test evidenced the higher corrosion resistance of the coated samples compared to the bare surfaces for both alloys. The potentiodynamic tests showed that the corrosion current density decreased for coated AA7075-T6 and AA2024-T3 alloys, which indicated an obvious improvement of the corrosion resistance with all the processes for both alloys. Although the corrosion resistance of the coated samples appeared to be higher for the alloy AA7075-T6 than for the alloy AA2024-T3, both alloys achieved the best corrosion protection with the coatings deposited from conversion bath formulations containing no titanium salts. The microscopy analysis on the coated AA7075-T6 samples revealed that a local deposition of Zr compounds and, possibly, an oxidation process occurred in the vicinity of the alloy's intermetallic particles. The amount of the Zr deposits at these locations increased with coating's formulations without Ti, which provided the best corrosion resistance. The Cr-free conversion coatings developed in this study for the AA7075-T6 and AA2024-T3 alloys do not meet yet the strict requirements of the aircraft industry. However, they significantly improved the corrosion performance with respect to the bare alloys and could be a good starting point for further studies and optimization.Item Corrosion performance of anodic films containing polyaniline and TiO2 nanoparticles on AA3105 aluminium alloy(2008-08-15) Zubillaga, O.; Cano, F. J.; Azkarate, I.; Molchan, I. S.; Thompson, G. E.; Cabral, A. M.; Morais, P. J.; SISTEMAS FOTOVOLTAICOS; SG; Tecnalia Research & InnovationThe corrosion protection afforded to an AA3105 aluminium alloy supporting an anodic film with incorporated polyaniline and TiO2 nanoparticles has been examined. The films were synthesised by simultaneous anodizing and electropolymerisation of aniline in the presence of nanoparticles. The morphology and composition of the films were probed by TEM, SEM, rf-GDOES and XPS. The resultant coatings comprised a thin porous anodic film of 2-3 μm thickness, with an outer hybrid polyaniline/TiO2 layer of several tens nanometres thickness, with the dimensions of TiO2 nanoparticles being below 10 nm. Electrochemical impedance spectroscopy analysis and salt spray testing revealed that TiO2 containing films provide improved corrosion protection to the AA3105 aluminium alloy compared with the film without nanoparticles. The improved protection provided by the coatings containing TiO2 nanoparticles is attributed to the TiO2 particle-rich thin film layer formed on the outer part of the coating that acts as a blocking barrier layer for the anodic porous aluminium oxide film.Item Design of Corrosion Protective and Antistatic Hybrid Sol-Gel Coatings on 6XXX AlMgSi Alloys for Aerospace Application(2020-04-30) Agustín-Sáenz, Cecilia; Santa Coloma, Patricia; Fernández-Carretero, Francisco J.; Brusciotti, Fabiola; Brizuela, Marta; Tecnalia Research & Innovation; VALORIZACIÓN DE RESIDUOS; TECNOLOGÍAS DE HIDRÓGENO; INGENIERÍA DE SUPERFICIESAn inorganic–organic coating based on glycidyl-functionalized silica and zirconia was synthesized by sol-gel technology to protect three types of AlMgSi (6XXX series) alloys against corrosion in aerospace applications. Different parameters such as the solid content, the organic/inorganic ratio of the sols and the deposition conditions were studied with the aim to achieve a tradeoff between the corrosion protection, antistatic performance and low vacuum-induced outgassing. Those parameters directly influence the thickness and the density of the coatings, and therefore the barrier effect against corrosion and the contact electrical resistance, which are affected in opposite ways. To obtain a low contact electrical resistance, silver nanowires (NW) with a high aspect ratio were loaded in the sol-gel matrix with the aim to create a conductive path through the hybrid coating with a low concentration of NWs. The coatings were adapted for AA6063, AA6061 and AA6082, and they all showed an outstanding anti-corrosion performance in different artificial weathering tests, whereas electrochemical impedance spectroscopy permitted the identification of the most critical parameters affecting water uptake. An antistatic performance was demonstrated by the low contact electrical resistance of the coated AA6061 and AA6063 alloys, although the incorporation of NWs showed a detrimental effect on the corrosion protection compared with the unloaded coatingItem Effect of organic precursor in hybrid sol–gel coatings for corrosion protection and the application on hot dip galvanised steel(2019-01-15) Agustín-Sáenz, Cecilia; Martín-Ugarte, Eider; Jorcin, Jean Baptiste; Imbuluzqueta, Gorka; Santa Coloma, Patricia; Izagirre-Etxeberria, Usoa; Tecnalia Research & Innovation; VALORIZACIÓN DE RESIDUOS; MATERIALES PARA CONDICIONES EXTREMAS; SISTEMAS FOTOVOLTAICOS; INGENIERÍA DE SUPERFICIESSol-gel coating material with enhanced corrosion protection for zinc-coated steel has been obtained through the incorporation of mono-phenol and bi-phenol organic precursors in an epoxide functionalised-silica-zirconia matrix. The effect of the presence of the organic precursors in the baseline formulation has been studied; sol stability has been examined by viscosity evolution; gel densification stage has been studied by differential scanning calorimetry (DSC); material composition has been analysed by Fourier transform infrared spectroscopy (FTIR) and X-ray spectroscopy (XPS); coating thickness and roughness has been measured by profilometry. Corrosion performance in three artificial weathering tests showed outstanding performance in the delay of zinc and steel corrosion products emergence, and electrochemical impedance spectroscopy (EIS) measurement permitted the identification of the coating presenting the most promising properties in terms of corrosion protection. Developed coatings have shown outstanding contribution to service life extension of zinc-coated parts.Item Evaluation of Anticorrosion Coatings for Offshore Wind Turbine Monopiles for an Optimized and Time-Efficient Coating Application(2022-03-14) Marinova, Nevena; Urbegain, Aiala; Benguria, Pablo; Travé, Andreu; Caracena, Raúl; MATERIALES PARA CONDICIONES EXTREMASOffshore corrosion is a critical issue for metallic offshore structures. In this study, we investigated the corrosion protection of 12 coating systems for offshore monopiles in atmospheric, splash, and submerged zones, and we compared their performance under accelerated laboratory testing according to ISO 12944 with real field exposure. The results showed that the aging of the coatings did not accelerate at the same rate in all coatings. Furthermore, we observed that for some types of laboratory tests, the results are not representative of real field exposure as the laboratory test is much less aggressive than the real offshore conditions. This observation confirms that the field exposure data provide valuable information in order to properly assess the corrosion protection of coatings and thus the expected lifetime of the offshore structure. Additionally, we analyzed the rate-determining steps involved in the application of the coating onto the entire monopile and quantified the possibility of achieving a more time efficient coating process. Our results contribute to a better understanding of the issues related to testing and qualification of corrosion protection coatings for offshore structures and provide useful insights for the selection of coating solutions at the industrial level.Item Polyaniline and nanoparticle containing anodic films for corrosion protection of 2024T3 aluminium alloy(2009-11) Zubillaga, O.; Cano, F. J.; Azkarate, I.; Imbuluzqueta, G.; Insausti, M.; SISTEMAS FOTOVOLTAICOS; SG; Tecnalia Research & Innovation; MATERIALES PARA CONDICIONES EXTREMASAnodic alumina films containing polyaniline and TiO2 or ZrO 2 nanoparticles were electrochemically synthesised on an AA2024T3 aluminium alloy in a single step anodising process carried out in oxalic acid electrolyte containing aniline and nanoparticles. The morphology and composition of the films were examined by scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. The resultant coatings, with a thickness of ∼2·5 mm, presented a polyaniline and nanoparticle rich layer in the near surface region, with a thickness in the range of 150-250 nm. The electrochemical polarisation curves revealed that the TiO2 containing films provide improved corrosion protection to the AA2024T3 aluminium alloy, showing a passive current density two orders of magnitude lower than the films with ZrO2 nanoparticles and the films without nanoparticles. The improved corrosion protection offered by the TiO2 nanoparticle containing coatings is attributed to the presence of the nanoparticle rich layer formed on the outer part of the coating, which acts as a barrier layer that blocks the pores of the anodic alumina film.