Impact of the final thermal sealing of combined zinc/cerium oxide protective coating primers formed on low carbon steel

Abstract

The final sealing possesses a proven beneficial effect on the protective properties of anodic oxide films on aluminum. In this sense, the present research is devoted to the evaluation of the impact of this procedure on the barrier ability of combined Zn/Ce oxide layers deposited on low carbon steel samples. For this purpose, four samples were submitted to galvanic zinc deposition, followed by spontaneous formation of cerium oxide primer layer (CeOPL). Afterwards, two of the samples underwent thermal sealing in boiling water in order to enhance their barrier ability. Its evaluation was performed by two electrochemical methods: electrochemical impedance spectroscopy (EIS) and potentiodynamic scanning (PDS) after 24 hours of exposure to a diluted model corrosive medium (MCM). Other instrumental methods were used in order to describe the effect of this final procedure on the color characteristics and hydrophobicity of the films. The results were collected from multiple tests, followed by statistical data treatment. In addition, the surfaces of the obtained films were submitted to direct observation by scanning electron microscopy (SEM), coupled with energy dispersion X-ray (EDX). Their composition was determined by means of X-ray Photoelectron Spectroscopy (XPS). The acquired data have revealed a detrimental effect of the final sealing in boiling water. It was expressed by the loss of the barrier properties of the Zn/CeOPL films, combined with additional decolorization and hydrophilization. Finally, the mechanism of this detrimental effect was determined by further SEM, EDX and XPS analyses.

Innovative Applications of Cerium Oxide-Based Materials in Civil Engineering, Automation, and Energy Sectors

“…Recent evidence suggests that the optimal concentration of the Ce-precursor should range between 0.03 and 0.05 mol dm À3 [98,99], and the maximum amount of added 30% H 2 O 2 as a deposition activator should be around 10 ml for up to 1000 ml of precursor solution. Experiences thus far indicate that the deposition of these coating layers can be accomplished through dipcoating [96,97], electrodeposition under galvanostatic [46] or potentiostatic [100,101] regimes. In all cases, CeCC formation requires activation energy in the form of elevated temperatures (up to 60°C to avoid considerable thermal H 2 O 2 decomposition), applied potential (up to À1 V) vs. Ag/AgCl reference electrode, or defined current density (from À2toÀ5mAcm À2 ).…”

Advances in processing and characterization of conversion coatings

“…The second group of articles presented in this special issue is related to new achievements in tailoring CCs for corrosion protection. The sacrificial ZnFe alloy coating electrodeposited on steel was further modified by a hybrid sol-gel silane coating [7], while electrodeposited Zn coating on steel was modified by electroless cerium oxide layer deposition and additional sealing in boiling water [8]. Ce was also used in [9] as a dopant in hydrotalcite-type protective chemical conversion coatings on aluminium alloy AA 7075.…”