Wettability Behavior of Zinc-Based Alloys on Cast Iron

The wettability of two Zn–Al alloy coatings (called “McGill 2” and “McGill 3” with 27 and 10 wt% Al, respectively) on the compacted graphite cast iron substrate was studied using the static sessile drop method. The effects of wetting time and coating composition on the macrostructural and microstructural evolution of the system were investigated. It was found that although the contact angle was obtuse for both coating materials over the time, the interfacial reactions occurred between the drop and the substrate from the first stage of contact. The most significant result was the formation of a uniform and thick reaction layer (interlayer) with the diffusion-controlled property at the interface. The results showed that “McGill 2” coating is superior to “McGill 3” alloy as an intermediate material for the Al–Fe cast joining application. The “McGill 2” interlayer revealed a composite nature as it consisted of different layers of solid, in the form of stable Al _x Fe _y Si _z intermetallic phases from the initial steps of the reactions.