Niobium pentoxide coating replacing zinc phosphate coating

P R P Rodrigues,A C Lopes,I Costa,O R A Junior,E P Banczek,M Terada

doi:10.1590/s1517-70762014000200005

Abstract

A new coating made of niobium pentoxide, obtained through the sol-gel process, was developed for the carbon steel (SAE 1010). The corrosion protection provided by this coating was evaluated through electrochemical tests such as: open circuit potential, electrochemical impedance spectroscopy and anodic potentiodynamic polarization in NaCl 0,5 mol L-1 solution. The morphology and composition of the coatings were analyzed using scanning electronic microscopy, energy dispersive spectroscopy and X-ray diffractions. A zinc phosphate coating was used as standard test for comparison of results. The electrochemical measurements revealed that: (1) The Nb2O5 coating dislocates the corrosion potential towards more positive values; (2) higher impedance values were found for the Nb2O5 coated samples; and (3) lower current density values were found for these samples. The electronic micrograph revealed that there was alteration in the morphology of the carbon steel surface due to the Nb2O5 deposition. The EDS spectra confirmed the niobium coating deposition, as a peak regarding this element was obtained in the spectra. The X-ray diffractograms confirmed the presence of the phases in the Nb2O5 coating. This new coating increases protection of the carbon steel against corrosion and presents an alternative to replace phosphating.

Highlights

Niobium oxides are new materials, with new applications based on their piezoelectric and ferroelectric properties with promising applications in electromechanics, non-linear optics, and other technological fields, presenting environmental compatibility [1,3]
A new coating for carbon steel based on niobium pentoxide was developed in this study and the following conclusions were obtained from the characterization of such coating
The open circuit potential curves demonstrated that the Nb2O5 coating dislocated the corrosion potential of the carbon steel towards more positive values and this result suggests that this layer provides more resistance to corrosion

Summary

Introduction

Niobium oxides are new materials, with new applications based on their piezoelectric and ferroelectric properties with promising applications in electromechanics, non-linear optics, and other technological fields, presenting environmental compatibility [1,-3]. These compounds can be used for water decomposition in hydrogen and oxygen [4,5]. There are reports on niobium oxides obtained on several materials surfaces [6, 10]. The niobium pentachloride, in turn is an economically advantageous precursor in relation to the ethoxide and in the literature available there are no references regarding its use as an anchor

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Results

Conclusion