Improvement of the electrochemical behaviour of Zn-electroplated steel using regenerated Cr (III) passivation baths

Abstract

ElsevierGarcía Antón, J.; Fernández Domene, RM.; Sánchez Tovar, R.; Escrivá Cerdán, C.; Leiva García, R.; García, V.; Urtiaga, A. (2014). Improvement of the electrochemical behaviour of Zn-electroplated steel using regenerated Cr(III) passivation baths. AbstractConversion coatings based on trivalent chromium are more sensitive to the presence of zinc and iron impurities than the chromate formulations. This fact contributes to a decrease in the quality of passivation and to the generation of a significant amount of hazardous liquid waste. Recently, a new eco-innovative process based on Emulsion Pertraction Technology (EPT) is being implemented at industrial scale for selectively removing Zn and Fe from spent passivation baths in order to enhance the lifetime of the Cr (III) baths. In this study, the effect of Zn and Fe removal on the electrochemical behaviour of Zn-electroplated steel samples was evaluated by means of polarisation curves and electrochemical impedance spectroscopy measurements at open circuit potential conditions in 3.5 g/L NaCl solutions. The main objective was to assess the benefits brought by EPT using electrochemical methods. Cr (III) passivation baths regenerated using the EPT process have been compared to the bath used in a local industry as well as to fresh and spent baths. According to the results, the samples passivated in the EPT regenerated bath showed a significant improvement in their electrochemical behaviour compared to the samples passivated in the spent baths. This study concluded the suitability of EPT for regenerating Cr(III) passivation baths.

Zn–Ni Alloy Plating with Trivalent Chromate: Effects of NaF Additive Concentration and Treatment Time on Film Color, Thickness, and Electrochemical Properties

“…However, the current density decreased with increasing NaF concentration. This indicates that the chromate film exists in a passive state, which suppresses the current density and improves the corrosion resistance by delaying corrosion, as determined in previous studies [10][11][12]. Because NaF affects the film formation, the effect of NaF concentration on chromate film formation was investigated [8,9].…”

Hardness and corrosion resistance of Zn−Mn/Al2O3 composite coatings produced by electrochemical deposition

“…4). The constant phase element (CPE) was used to describe the non-ideal behavior of the capacitive elements and to obtain higher goodness of fitting 24 . The fitted parameters of the constant phase element were later used to calculate the double layer capacitance values, using Echem Analyst software.…”

Electrochemical Evaluation of Corrosion Resistance of Trivalent Chromate Conversion Coatings with Different Organic Additives

“…The alkaline non-cyanide zinc plating solution and Cr 3 + -based passivation solution are environmentally-friendly chemicals that are available for these processes. [5][6][7] The key chemicals in the zinc plating solution include organic additives, [8][9][10] such as organic polyamine compounds, which affect the uniformity, leveling, and brightness of the zinc coatings.…”