Deposition and Characterization of a New Mixed Organic/Inorganic Cerium Containing Coating for the Corrosion Protection of Eletrogalvanized Steel (original) (raw)
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Evaluation of mechanically treated cerium (IV) oxides as corrosion inhibitors for galvanized steel
Electrochimica Acta, 2011
The use of cerium salts as corrosion inhibitors for hot dip galvanized steel has been object of a numerous studies in the last few years. The role of cerium ions as corrosion inhibitors was proved: cerium is able to block the cathodic sites of the metal, forming insoluble hydroxides and oxides on the zinc surface. This fact leads to a dramatic decrease of the cathodic current densities and, therefore, to a reduction the overall corrosion processes. On the other hand, the potential of cerium oxides as corrosion inhibitors was also proposed. However, the real effectiveness of this kind of anticorrosive pigments has not been clarified yet.
the Chemical Technology, 2014
Conversion coatings are used not only to impart corrosion protection but also to improve adhesion of paint systems/ metal surface. Chromate-based converJosé Daniel Culcasi1, Cecilia Inés Elsner1,2, Alejandro Ramón Di Sarli2*, Luis Palomino3, Célia Regina Tomachuk4, Isolda Costa4 1Engineering School, National University of La Plata, Av. 1 Esq. 47. CP. B1900TAG, La Plata, (ARGENTINA) 2Research and Development Centre in Paint Technology (CICPBA-CCT CONICET LA PLATA); Av. 52 s/n entre 121 y 122. CP. B1900AYB, La Plata, (ARGENTINA) 3Polytechnic School of the University of San Pablo (EPUSP), Engineering Chemistry Department, Av. Prof. Lineu Prestes, 580, Caixa Postal 61548, CEP 05508-970, São Paulo-SP, (BRAZIL) 4Energy and Nuclear Research Institute, IPEN/CNEN-SP, CCTM, Av. Prof. Lineu Prestes, 2242, CEP 05508-000, São Paulo, SP, (BRAZIL) E-mail: ardisarli@cidepint.gov.ar; ardisarli@gmail.com; cielsner@ing.unlp.edu.ar; tomazuk@gmail.com
International journal of electrochemical science
The aim of this work was to investigate the effect of the cerium concentration on the morphology and anticorrosion performance of cerium-silane hybrid coatings on hot dip galvanized (HDG) steel substrates. 3-glycidoxypropyltrimethoxysilane (GPTMS) and bisphenol A (BPA) were employed as precursors to prepare the sol-gel based silane coating. Cerium nitrate hexahydrate was added to the silane coatings as dopant in five different concentrations. The morphology of the coatings before and after the corrosion test was examined by scanning electron microscopy (SEM), indicating an effect of the cerium concentration. Very low and very high cerium concentrations deteriorate the corrosion inhibition in the sol-gel matrix and consequently, there is an optimum concentration of cerium nitrate. Accelerated salt spray testing showed that corrosion near an artificial scratch is blocked efficiently by high cerium nitrate contents, whereas uniform corrosion is inhibited effectively with comparatively low ceria contents. Electrochemical studies indicate a general beneficial effect of the incorporation of cerium nitrate, although the performance of the coated substrate depends on the cerium nitrate content. The results of electrochemical impedance spectroscopy (EIS) and electrochemical polarization confirmed that the corrosion resistance of the coatings initially increases and then decreases as the cerium concentration goes up. Optimal corrosion resistance was obtained at a cerium concentration of 0.05 M.
2011
This work is focused on the study of corrosion-protection ability of the thin ceria film, formed electrochemically on OC404 stainless steel (SS) in non-aqueous electrolytes. The influence of changes in the surface concentration of Ce 2 O 3-CeO 2 on the corrosion behaviour of OC404 stainless steel in 3.5% NaCl was investigated prior to the thermal treatment as well as after it. A shift of corrosion potential in positive direction was found via polarization curve recording, as well as via decrease in the corrosion current, respectively decrease in the corrosion rate (enhancement of the corrosion protection) in the presence of ceria oxide films. The data, acquired by AFM and XPS, are in a good agreement with these results. On the basis of the obtained results we can conclude that the presence of Ce 2 O 3-CeO 2 film results in passivation and re-passivation of the steel surface and a slowdown in the pitting corrosion in an aggressive media. These conclusions are explained by the strong polarization influence of the Ce 2 O 3-CeO 2 layers on the conjugated depolarization cathodic reaction of reduction of the dissolved oxygen.
Corrosion Science, 2008
Cerium oxide based films on carbon steel were deposited using a cathodic electrodeposition approach and from relatively concentrated solutions. The effects of the relatively high cerium nitrate concentrations (0.1 and 0.25 M) and of applied current density (0.25 mA cm À2 6 j 6 3 mA cm À2) on the composition and microstructure of the films were thoroughly investigated with the support of scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman and Fourier transformed infrared (FTIR) spectroscopies. The results showed that the use of 0.25 M solutions brought about immediate formation of the films compared to the 0.1 M. As the applied current density was increased, the time elapsed for achieving a stabilisation of the potential decreased. Also, the CeO 2 crystallite size decreased with increasing applied current density. However, at high cathodic current densities, the crystallite size was similar regardless of the concentration, hence suggesting that the precipitation mechanisms became predominant. CeO 2 was the major species deposited on carbon steel. Ce(OH) 3 was also well distinguished in the deposits elaborated from 0.25 M solutions. Both concentrations led to the formation of a carbonated green rust in which some carbonates were probably replaced by nitrate anions. The mechanisms of formation of the green rust and its evolution with time are also elucidated in this work.
Effect of the temperature of cerium nitrate–NaCl solution on corrosion inhibition of mild steel
Materials and Corrosion
In this work, the effect of temperature on corrosion inhibition was studied in the absence and presence an optimal concentration of cerium nitrate (600 mg.L-1) as an inhibitor of mild steel in sodium chloride. Corrosion tests were carried out through electrochemical techniques such as impedance spectroscopy and d.c polarization measurements. The surface morphology of the films was investigated by optical microscopy (MO), white light interferometry (WLI) and a scanning electronic microscopy (SEM) coupled to EDS analysis for chemical composition. The results obtained show that the activation energy for the corrosion inhibition process to occur increased in the presence of cerium nitrate inhibitor. However, the corrosion resistance of mild steel was somewhat lost with increasing the solution temperature up to 55 °C, which lead to more cracked films. The enthalpy and entropy values suggested a mixed mechanism of chemisorption and physisorption inihibition, with a major dominant of physisorption control.
Corrosion Science, 2004
A golden yellow-colored cerium conversion coating was obtained on 304 stainless steel surface by immersing the steel into a solution containing cerium (III), KMnO 4 and sulfuric acid. The corrosion resistance of the coatings was evaluated by electrochemical methods, potentiodynamic polarization experiments and electrochemical impedance spectrum. The experimental results indicated that the corrosion resistance for the conversion coated 304SS in 3.5% NaCl solution increased markedly. The corrosion potential of the treated steel increased to a more noble level, the pitting corrosion potential increased also, the passive potential range was enlarged markedly and the passive current density decreased about one order compared to that of the untreated steel. The cathodic and anodic reaction were both inhibited to some extent. The chemical state of the elements in the coatings was investigated by XPS. The cerium element was in the form of tetravalent state. And AES depth profile analysis suggested that the thickness of the conversion coatings was less than 66 nm. The mechanisms of coatings formation and corrosion resistance are discussed.
Corrosion protection properties of cerium layers formed on tinplate
Corrosion Science, 2004
Corrosion protection properties of cerium-passivated, unpassivated and chromium-passivated tinplates in contact with a 0.1 M citric-citrate buffer solution were studied using polarisation (DC) and electrochemical impedance spectroscopy (EIS) methods. The morphology and composition of the passive layer were studied using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS) in conjunction with argon-ion sputtering. Cerium-passivated tinplate showed similar corrosion properties to chromium-passivated tinplate in DC measurements, while the latter yielded the best corrosion resistance results in EIS measurements. SEM and EDX illustrated spherical particles with iron, cerium and tin contributions. XPS measurements indicated that the cerium-rich coating was a hydrated oxide with a composition of cerium(III): Ce(OH) 3 and cerium(IV): CeO 2 and Ce(OH) 4 .
Corrosion Science, 2006
The corrosion inhibition mechanisms of new cerium and lanthanum cinnamate based compounds have been investigated through the surface characterisation of the steel exposed to NaCl solution of neutral pH. Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy was used to identify the nature of the deposits on the metal surface and demonstrated that after accelerated tests the corrosion product commonly observed on steel (i.e. lepidocrocite, c-FeOOH) is absent. The cinnamate species were clearly present on the steel surface upon exposure to NaCl solution for short periods and appeared to coordinate through the iron. At longer times the Rare Earth Metal (REM) oxyhydroxide species are proposed to form as identified through the bands in the 1400-1500 cm À1 region. These latter bands have been previously assigned to carbonate species adsorbed onto REM oxyhydroxide 0010-938X/$ -see front matter Ó (M. Forsyth).