ИСТИНА

The kinetics of P incorporation during Ni-P, Co-P and Fe-P electrodeposition were investigated by means of interfacial pH measurements cathodic polarization curves and electron probe microanalysis. This process is strongly affected by solution pH. A buffering effect provided by sodium hypophosphite in the solution was observed at pH 2. By contrast at pH 5.5 this effect was not observed and an increase in the degree of alkalination at the interface was verified. At pH 2 Ni2+, Co2+ and Co3+, Fe 3+ ions redaction was strongly disfavored during Ni-P, Co-P and Fe-P depositions. The mechanism of this deposition was modified by the presence of NaH2PO2aq in the solution. The characteristic time constants for the individual cathodic process H+, metals ions and hypophosphite redaction could be identified during co -deposition. Moreover at pH 5.5 Ni-P, Co-P and Fe-P deposition occurs by means of a different mechanism than that observed at pH 2. Another interesting feature concerns the diagrams obtained in the 0.23 M hypophosphite (aq) solution similar to the one obtained at pH2 the mechanism of co deposition in alkaline medium. Indeed given that no buffering effect occurs at this pH value and this reaction take place throe reduction process a strong increase in the interfacial pH was observed.