Zn-Co alloy coatings were electrodeposited from sulphate-based bath. So as to elaborate homogeneous and fine grained deposit on mild steel, the effect of additive and baths’ parameters on the coatings’ morphology, at distinct temperatures (17 and 24 ℃), were studied and discussed. Firstly, at each indicated temperature, the experimental results laid out that bath parameters had a significant effect on the Co content and consequently, coating’s morphology. In fact, SEM observations showed that apply −1.2 V as potential changed remarkably the layers’ surface from cracked to uniform and well covered surface. Moreover, while, sodium as additive allowed transforming coatings’ morphology to a nodular structure with 22.6 wt% Co, pH adjustment to 1.7 was able to deposit smoother structure with only 5 wt% Co. On the other hand, temperature was a major factor to modify the layers’ morphology. Indeed, despite the similar Co contents deposited at 17 and 24 ℃, coatings developed at 24 ℃ exhibited smoother surface and finer structure. XRD analysis showed that coatings, with a nanocrystalline structure (45 ± 5 nm) and a single intermetallic phase, were developed at 24 ℃ with appropriate parameters (−1.2 V, pH adjusted, sodium addition).