THE MECHANISM OF PHOSPHORUS INCORPORATION DURING THE ELECTRODEPOSITION OF NICKEL-PHOSPHORUS ALLOYS

Phosphine was detected and quantified during the electrodeposition of nickel-phosphorus alloys. The presence of PH3 supports the indirect mechanism of phosphorus incorporation: the phosphorus oxyacid in the bath is reduced to phosphine, which then undergoes a redox reaction with Ni2+ to produce both phosphorus and nickel in the elemental form. Phosphine is produced more readily from hypophosphorus acid than from phosphorus acid. Phosphine production from hypophosphorus acid is favored by low pH, and facilitated by the presence of nickelous ion. The latter effect may result from the release of hydrogen ions in the redox reaction involving PH3 and Ni2+.