Effects of Carrier, Leveller, and Booster Concentrations on Zinc Plating from Alkaline Zincate Baths

Abstract

Organic additives are required for alkaline zincate plating baths to obtain an acceptable coating on steel for corrosion protection. The effects and possible interactions of three commercial additives (Eldiem Carrier, Eldiem Booster, and Bright Enhancer 2× on zinc electrodeposition from a high-concentration alkaline zincate bath were investigated. Visually acceptable deposits were produced within the current density range of 130 to 430 A m−2 for most additive conditions examined. Over concentration ranges examined, decreasing the booster concentration led to brighter zinc deposits, and an interaction between the carrier and the booster was detected. The additives fostered the formation of compact and adherent coatings as illustrated by scanning electron microscopy. Throwing power and current efficiency were not impacted by the additives over the concentration ranges examined. Linear sweep voltammetry proved that the additives increased the overpotential for zinc deposition. The additive combination that produced the brightest deposit also demonstrated the strongest adsorption of additives in linear sweep voltammetry.

Effects of Organic Additives on Alkaline Non-Cyanide Zinc Electroplating

“…The throwing power depends on plating parameters such as the zinc concentration, pH, current density, temperature, and plating duration. Some studies have shown that additives can improve the throwing power in non-cyanide zinc plating baths [1]. Figure 13 shows the throwing power (TP (%)) and metal precipitation weight ratio (M) of both cathode specimens according to the composition of the additives added and without additives at a current density of 2 ASD (A/dm 2 ).…”

“…To prevent corrosion, structural steel must be coated with a less corrosive metal, paint, or enamel. Zinc provides good protection for steel because of its relatively low corrosion rate [1].…”

“…It can also produce a uniform, bright, and adherent coating on steel. Electro-galvanizing is often preferred over hot-dip galvanizing when a decorative finish is required [1,2].…”

“…However, their use has declined over time because of cyanide toxicity and the increasingly stringent environmental regulations. Electro-galvanizing technology has shifted to using less toxic acid zinc and alkaline zincate (non-cyanide) baths [1,3].…”

“…However, because there is no effect of the complexation of cyanide, unattached precipitates in powder form are generated in the alkaline non-cyanide galvanizing bath. Therefore, plating additives are required in alkaline non-cyanide galvanizing baths to produce smooth and adherent zinc plating [1][2][3][4][5].…”