AUTOCATALYTIC EFFECTS IN ELECTROLESS DEPOSITION OF PALLADIUM

This paper deals with the catalytic aspect of electroless palladium de position on Pd-Sn activated stainless steel substrates. Experimental r esults of anodic hydrazine polarization revealed that the shape of the polarization curves can be taken as an indicator of the catalytic act ivity of substrates. The exchange potential reflects the nature of the palladium species, while the reference current density at a given pot ential depends on the amount of the active species. X-ray photoelectro n spectroscopy and polarization measurements showed that the presence of tetravalent Pd(IV) oxide limits the autocatalytic activity of activ ated substrates. The Pd(IV) species is very likely stabilized by inter action with the coexisting SnO2 on the Pd-Sn activated substrate. Pred eposited palladium exists in large proportion as metallic palladium wi th some Pd(II). In the reductive hydrazine solution, the latter specie s may easily be reduced and become active for electroless plating.