Characterization of amorphous Co–P alloy coatings electrodeposited with pulse current using gluconate bath

► Co–P alloys are electrodeposited with pulse current using gluconate bath. ► Alloy coatings are amorphous in nature with different P contents. ► As-deposited alloys consist of Co0, Co2+ and Pδ−, P5+ species. ► Increase in the amounts of Co0 and Pδ− is observed upon intermittent sputtering. ► Heat treated coatings show average microhardness values of 940HK. Co–P alloy coatings were electrodeposited with pulse current using gluconate bath and characterized by XRD, FESEM, AFM, DSC and XPS. Co–P alloy coatings are amorphous in nature as demonstrated by XRD. FESEM exhibits the “cauliflower type” morphology that is distinctive of nanocrystalline metals and alloys. Co–P alloys are found to follow instantaneous growth mechanism as revealed by AFM studies. Two exothermic peaks at 320 and 340°C in DSC profiles of Co–P deposit correspond to the crystallization of the deposit. Detailed XPS studies of these alloy coatings have shown that as-deposited coatings consist of Co metal as well as oxidized Co species. P has mostly been present as bulk alloy on the surface as Pδ− form. Increase in the amounts of Co metal and Pδ− are observed upon intermittent sputtering. No appreciable increase in microhardness is observed with increase in the phosphorous content, but it increases with heat treatment significantly.