Aminoacetic acid as complexing agent in baths for electroless deposition of Ni–W–P coatings

Abstract

Ni–W–P alloy coatings were deposited from a bath containing, nickel sulphate (VI), sodium tungstate (VI), sodium hypophosphite, sodium formate, and a complexing agent. The complexing agents were formic acid, acetic acid, lactic acid, succinic acid, malic acid, malonic acid, aminoacetic acid and triethanoloamine. It is shown that Ni–W–P coatings are deposited the slowest when complexing agents with the highest stability constants are used. As the deposition rate increases, i.e. in the presence of less stable complexing compounds, the amount of tungsten in the coating decreases. When aminoacetic acid and citric acid were used, the tungsten content in the coating amounted to ∼2 wt-%, depending on the complexing agent concentration and the pH of the bath.