Browsing by Keyword "Corrosion protection"
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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 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.