Adhesion and corrosion behaviour of Zn–Co electrodeposits on mild steel

▶ The Zn–Co alloy coatings consisted of zinc solid solution and γ 2 Zn–Co intermetallic phase (CoZn 13). ▶ The adhesive load (LA) of the Zn–Co coatings to the mild steel was observed to decrease slightly with increasing alloy coating thickness. ▶ The Zn–Co alloy coatings act as sacrificial anodes to the mild steel substrates. Zn–Co alloy coatings of various thicknesses were electrodeposited on mild steel substrate, using a sulphate bath. SEM, EDS and XRD were used to study surface morphology, chemical composition and phase structure of the produced coatings. The microhardness of the produced coatings and the adhesive strength between the Zn–Co alloy coatings and the mild steel substrate were examined. The corrosion behaviour of the coated mild steel specimens in 0.1 M NaCl solutions, having different pH values, was also investigated by means of potentiodynamic corrosion experiments. The results showed that the corrosion resistance of the Zn–Co coated mild steel specimen was lower in acidic and alkaline than in neutral solutions. The corrosion products formed on the surface of the alloy coatings were analysed with the aid of a Scanning Electron Microscope (SEM) and an X-ray Diffractometer (XRD).