AUTOCATALYTIC EFFECTS IN ELECTROLESS DEPOSITION OF PALLADIUM

This paper deals with the catalytic aspect of electroless palladium deposition on Pd-Sn activated stainless steel substrates. Experimental results of anodic hydrazine polarization revealed that the shape of the polarization curves can be taken as an indicator of the catalytic activity of substrates. The exchange potential reflects the nature of the palladium species, while the reference current density at a given potential depends on the amount of the active species. X-ray photoelectron spectroscopy and polarization measurements showed that the presence of tetravalent Pd(IV) oxide limits the autocatalytic activity of activated substrates. The Pd(IV) species is very likely stabilized by interaction with the coexisting SnO2 on the Pd-Sn activated substrate. Predeposited palladium exists in large proportion as metallic palladium with some Pd(II). In the reductive hydrazine solution, the latter species may easily be reduced and become active for electroless plating.