Structure determination of electrodeposited zinc-nickel alloys: thermal stability and quantification using XRD and potentiodynamic dissolution

Electrodeposited zinc-nickel coatings obtained by electrodeposition reveal the presence of metastable phases in various quantities, thus requiring their identification, a study of their thermal stability, and, finally, determination of their respective proportions. By combining XRD measurement with partial potentiodynamic dissolution, anodic peaks were indexed to allow their quantification. Quantification of electrodeposited zinc-nickel alloys approximately 10 mu m thick was thus carried out on nickel content between 1.2% and 20%, and exhibited good accuracy. This method was then extended to the same set of alloys after annealing (250 degrees C, 2 h), thus bringing the structural organization closer to its thermodynamic equilibrium. The result obtained ensures better understanding of crystallization of metastable phases and of phase proportion evolution in a bi-phasic zinc-nickel coating. Finally, the presence of a monophase gamma and its thermal stability in the 12% to 15% range provides important information for coating anti-corrosion behavior. (C) 2016 Elsevier Ltd. All rights reserved.