CHARACTERIZATION AND HARDNESS OF Co–P COATINGS OBTAINED FROM DIRECT CURRENT ELECTRODEPOSITION USING GLUCONATE BATH

Direct current electrodeposition of Co–P alloy coatings were carried out using gluconate bath and they were characterized by employing techniques like XRD, FESEM, DSC and XPS. Broad XRD lines demonstrate the amorphous nature of Co–P coatings. Spherical and rough nodules are observed on the surface of coatings as seen from FESEM images. Three exothermic peaks around 290, 342 and 390°C in DSC profiles of Co–P coatings could be attributed to the crystallization and formation of Co2P phase in the coatings. As-deposited coatings consist of Co metal and oxidized Co species as revealed by XPS studies. Bulk alloy P (Pδ-) as well as oxidized P (P5+) are present on the surface of coatings. Concentrations of Co metal and Pδ- increase with successive sputtering of the coating. Observed microhardness value is 1005 HK when Co–P coating obtained from 10 g L-1 NaH2PO2 is heated at 400°C that is comparable with hard chromium coatings.