Sliding wear behaviour of zinc–cobalt alloy electrodeposits

The wear behaviour of zinc–cobalt electrodeposited coatings on copper substrates was investigated, using a pin-on-disc wear apparatus. The composition of the zinc–cobalt alloy coatings was the following: Zn–0.6 wt.% Co and Zn–4 wt.% Co respectively. The friction coefficient of Zn–4 wt.% Co coatings against stainless steel was found to be similar to that of Zn–0.6 wt.% Co coatings against the same steel. The normalized weight loss of Zn–4 wt.% Co coatings was found to be higher than that of Zn–0.6 wt.% Co coatings. The main wear mechanism for the Zn–0.6 wt.% Co coatings was found to be severe shearing of the coatings surface layers, due to the plowing action of the stainless steel pins. For the Zn–4 wt.% Co coatings the predominant wear mechanism was noted to be intensive surface delamination leading to spalling and brittle fracture of the coatings surface layers.