SVET study of the corrosion protection of electrodeposited Zn and Zn‐Co‐Fe alloy coated steels

The scanning vibrating electrode technique (SVET) was applied to study the corrosion resistance of partially coated (Zn and various Zn‐Co‐Fe alloys) and partially exposed steel samples in 10 mM NaCl solution. The sacrificial properties and the protection range decreases with increase in Co content in the alloy. For high Co content in the alloy, the coating becomes more noble to steel and loses its sacrificial protection. The barrier resistance of the coatings increases with the increase in Co content in the alloy coating. Zn‐Co‐Fe alloys with high Co content (i.e., 32 wt% Co and 1 wt% Fe) showed excellent barrier properties due to passivation after dezincification protecting the underlying steel. An intermediate region of compositions can be distinguished in which the coatings provide a good combination of sacrificial and barrier resistance properties and also a reasonable protection range.