Niobium pentoxide coating replacing zinc phosphate coating

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 Nb 2 O 5 coating dislocates the corrosion potential towards more positive values; (2) higher impedance values were found for the Nb 2 O 5 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 Nb 2 O 5 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 Nb 2 O 5 coating. This new coating increases protection of the carbon steel against corrosion and presents an alternative to replace phosphating.

Niobium- and titanium-based coating for the protection of carbon steel SAE 1020 against corrosion

“…Under higher magnification, a needle-like crystal structure was identified, as shown in Figure 3. Similar crystals were observed in the literature for a Nb 2 O 5 coating in carbon steel prepared by the Pechini method (Rodrigues et al , 2014) and for niobium oxide deposits generated after immersion in NaOH and H 2 SO 4 solutions (Chukwuike et al , 2021). The presence of the crystals on the material surface broadens the potential applications of the coating.…”