Preparation of fibrous CoMo/Al2O3 hydrotreating catalysts by the sol-gel method

Petrov, L.; Spasov, L.; Dimitrov, Philip; Vladov, Ch.

doi:10.1007/bf02129868

Cited by 3 publications

(2 citation statements)

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“…[34][35][36][37][38][39][40] Several studies have demonstrated 41-44 that the mechanical and electrical properties of these materials make them suitable pre-treatments to improve the corrosion resistance of several metals and alloys.…”

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“…Sol-gel process became an important field of research during the last years and have been shown to be an adequate route to produce OIH coatings. [34][35][36][37][38][39][40] Several studies have demonstrated [41][42][43][44] that the mechanical and electrical properties of these materials make them suitable pre-treatments to improve the corrosion resistance of several metals and alloys.…”

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Ureasilicate Hybrid Coatings for Corrosion Protection of Galvanized Steel in Cementitious Media

Figueira

Silva

Pereira

et al. 2013

J. Electrochem. Soc.

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This study is focused on the electrochemical behavior and surface analysis of an eco-friendly organic-inorganic hybrid (OIH) coating for hot dip galvanized steel (HDGS) in contact with cementitious media. This treatment is a proposed alternative to replace toxic Cr(VI)-based pre-treatments used to control reactions between the zinc and wet concrete. HDGS samples were coated with two different sets of OIH gels obtained by a sol-gel process using a dip-coating method. Five distinct OIH matrices were obtained by reaction of functionalized metal-alkoxide (3-isocyanatopropyltriethoxysilane) with five different molecular weight diaminealkylethers. One set of HDGS samples was coated with each of the five pure OIH matrices and another was coated with similar matrices doped with Cr(III). The morphology of OIH coatings over HDGS surface was characterized by SEM/EDS. Similar films were prepared separately and the respective resistivity was measured by electrochemical impedance spectroscopy. Polarization resistance and macrocell current density were used to evaluate the corrosion protection properties of the HDGS coated samples in contact with cementitious media for a period of 74 days. Results showed that the produced coatings provide barrier properties that withstand the high pH of the electrolyte, protecting the HDGS when it first contacts cementitious media.The corrosion of steel in concrete is one of the major causes of structures degradation, requiring expensive rehabilitation. The use of hot dip galvanized steel (HDGS) has been recognized as an effective measure to increase the service life of reinforced concrete structures exposed to carbonation or to chloride ions. 1-3 The galvanized coating is a physical barrier that hinders the contact of aggressive agents with the steel substrate and the zinc layer acts as a sacrificial anode, protecting the steel against corrosion. 4,5 Immediately after the HDGS is embedded in fresh concrete, a highly alkaline environment, the zinc coating corrodes for a limited period (from several hours to a few days) until passivating surface layers are formed and concrete hardens. This initial corrosion process may lead to zinc consumption between 5 to 10 μm. 2 At the same time hydrogen is produced which may lead to the loss of adhesion between steel and concrete.Several corrosion studies reported the behavior of HDGS in contact with concrete media and in alkaline solutions. 2-21 However, uncertainties concerning the initial corrosion behavior of the galvanized coating when embedded in concrete still remains. The main literature about corrosion and passivation mechanisms of zinc in concrete environments, suggest that the formation of the protective layer due to zinc oxidation takes place with water reduction and subsequent hydrogen evolution. 9-11 Other authors claim that the formation of protective layer is related to the presence of oxygen at the concrete/rebar interface. 12,14,18 Andrade and co-workers, 11,22,23 found that at pH ≥ 12.5 zinc dissolution and hydrogen evolution takes place p...

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