Abstract

The effect of surfactants nonylphenolpolyethylene glycol (D1), dinaphthylmethane-4,4′-disulphonic acid (D2) and polyethylene glycol with molecular weight 400 (D3) on both nickel-zinc dust cementation kinetics and the structure of obtained deposits was investigated. Experiments were carried out in the presence of copper to increase the low cementation rate of nickel. The reaction of nickel cementation was found not to follow first-order kinetics due to hydrogen evolution which takes place along with the cementation reaction. Two rate regions were observed. Hydrogen evolution in the presence of D1 is lower than with D2, D3 and without surfactants. D1 and D3 decrease but D2 has no effect on nickel cementation. The influence of D1 and D3 is higher at the beginning of the process. Higher temperature improves nickel cementation only in the initial period. The structure of cementation products depends on the temperature. Uniform layers of lamellar crystallites on the surface of zinc particles were observed at 65°C with and without surfactants. At 85°C the morphology changes to massive spheroid formations of lamellar crystallites. The presence of D1 and D3 decreases both the crystallite size and deposit porosity. The lowest porosity was found in the presence of D3. The inhibition effect of D1 on the hydrogen evolution contributes to decrease in zinc consumption during the cementation of nickel.

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