Zinc-Nickel Alloy Electrodeposition – Influence of Triethanolamine

Abstract

Compared to pure zinc plating, zinc alloys provide several advantages. A zinc alloy generally offers superior sacrificial protection to steel since it corrodes more slowly than pure zinc. A search for a non-cyanide zinc plating bath resulted on the development of a zinc nickel sulphamate bath. To obtain better quality zinc-nickel deposits, triethanolamine was added to the bath. In this paper the influence of triethanolamine in zinc-nickel plating from sulphamate bath has been investigated through current efficiency measurements, cyclic voltammetry, scanning electron microscope, and X-ray diffraction techniques. In the presence of triethanolamine in the zinc-nickel sulphamate bath the current efficiency of alloy deposition increased to a maximum of 99% at the current density of 1.5 Adm -2 and thereafter decreased. TEA adsorbed on the electrode surface obeying Henry's isotherm. On mild steel surfaces, uniform smooth slate gray deposit with smaller crystallites was produced, in presence of TEA in solution, and the electrodeposits exhibited additional Zn(OH) 2 and γ-Ni 3 Zn 22 phases. Hydrogen evolution was suppressed by TEA and thereby current efficiency is increased for alloy deposition.Keywords: cyclic voltammetry, electrodeposition, triethanolamine, XRD, Zn-Ni. IntroductionPrecoated electrogalvanised Zn-Ni sheet has offered the automotive and computer industries a superior prefabricated stock resulting in much-improved corrosion resistance. The zinc-nickel alloy deposit has 90 -95% zinc [1] and the deposition is anomalous, i.e., the less noble metal, zinc, deposits preferentially. There are broadly two types of plating baths for Zn-Ni alloy, namely the acid type and the alkaline type [2,3]. The acid bath consists of a mixture of zinc and nickel salts, electrolytes, buffers and optional brighteners. In the alkaline type,

Effect of ethyl vanillin on ZnNi alloy electrodeposition and its properties

“…These in turn depend on bath composition, additives, current density, temperature and thickness of electrodepostion (Ravindran and Muralidharan 2007;Rizwan et al 2007;Shivakumara et al 2007;Rahman et al 2009). Chitharanjan reported the increase of nickel content, corrosion resistance and Vickers microhardness of the deposit with applied current density up to 3 A dm -2 .…”

Study of the effect of Triethanolamine as a chelating agent in the simultaneous electrodeposition of copper and zinc from non-cyanide electrolytes

“…http TEA has been used as a complexing agent to obtain alloys such as Zn-Ni. In these cases it has improved the current efficiency and has been added onto the cathode surface to promote uniform coatings [12]. It has also been used to decrease the difference in reduction potential between two different metals and to avoid Fe(OH) 2 precipitation due to the high hydroxide concentration of the ZnFe alloy [13].…”

Mechanisms of Triethanolamine on Copper Electrodeposition from 1-Hydroxyethylene-1,1-diphosphonic Acid Electrolyte

“…Similar to what was proposed by Ravindran Further increase of concentration of TEA caused the disappearances of second and third anodic peaks during zinc-nickel alloy electrodeposition from sulfamate bath. 15 The results indicate the addition of TEA can avoid the formation of Cu(OH) 2 on the surface of copper anode and ensure the continuous dissolution of the anode. By measuring the weight loss of copper anode, it was found that under the same amount of quantity of electric charge (1 A · h), the copper weight loss with a solution containing 0.114 M TEA was 5.9% higher than that without TEA.…”