Deposition current density-induced grain boundary engineering of electrodeposited cobalt coatings for enhanced electrochemical stability

Abstract

ABSTRACT Cobalt coatings were electrodeposited at different deposition current densities (10 mA·cm−2, 20 mA·cm−2, 30 mA·cm−2, 40 mA·cm−2, 60 mA·cm−2) over mild steel substrate. The coating deposited at 30 mA·cm−2 showed the highest corrosion resistance (Rp = 7515Ω·cm2) due to a higher fraction of Low energy grain boundary constitution (i.e. coincidence site lattices (CSLs) and low angle grain boundaries (LAGB)) and exhibited higher fraction of stabler Co3O4 passive oxide layer. The coatings electrodeposited at 60 mAcm−2 exhibited lower corrosion resistance (Rp = 1304 Ω·cm2) due to a higher fraction of high-angle grain boundaries and a higher fraction of relatively lesser stable Co(OH)2.