Influence of Sulfur-Containing Stabilizers on the Autocatalytic Deposition of a Nickel–Phosphorus–Tungsten Alloy

Abstract

The influence of such sulfur-containing stabilizers as thiourea, sodium bis(sulfopropyl) disulfide (SPS), thiamine chloride, and 2-mercaptobenzothiazole (2-MBT) on the elemental composition of an autocatalytically deposited nickel–phosphorus–tungsten alloy and coating deposition rate is studied. The introduction of the sulfur-containing additives into a citrate–succinate solution stabilizes the deposition of a Ni–P–W alloy within at least 60 min. Thiourea and thiamine chloride do not allow the formation of deposits simultaneously with a high tungsten content and at a satisfactory deposition rate. Stabilizers 2-MBT and SPS make it possible to conduct deposition at higher rates with a high tungsten content. Depending on the number of amino groups in the molecule, different effects of the stabilizer concentration on the fraction of codeposited sulfur are observed. In the cases of SPS and 2-MBT, the sulfur fraction increases linearly with an increase in the stabilizer content. The sulfur fraction in the coating remains unchanged with increasing concentration when thiourea is used, and the sulfur content decreases with increasing concentration for thiamine chloride.