Influence of annealing temperature on ζ-CrZn₁₃ formation in electrodeposited Zn–Cr coatings

ABSTRACT

Electrоdeposited Zn–Cr alloy coatings, containing 3.6, 5.4 and 9.4 mass % Cr were analysed by DSC and XRD. X-ray diffraction patterns of the samples show that when they are annealed to selected temperatures before and after the heat flow peaks of the DSC curve, there is an irreversible transition in all three alloys from η-(Zn, Cr) to ζ-CrZn₁₃ phase. With increasing Cr content, the start of the transition is shifted to higher temperatures (from 180 to 250°С). The η-(Zn) phase is predominant in the annealed alloy with the lowest content of Cr. In the case of the alloy with the highest Cr content, typical XRD lines of Cr appear along with those of the ζ-CrZn₁₃ phase. The Zn–Cr coating containing 5.4 mass % Cr transforms almost completely into ζ-CrZn₁₃ phase with insignificant traces of residual initial η-(Zn, Cr) phase.

KEYWORDS:

• Electrodeposition
• Zn–Cr alloy coatings
• annealing
• phase composition
• phase transition
• DSC
• XRD

Acknowledgement

The authors would like to thank voestalpine Stahl GmbH, Linz, Austria for providing samples used in the present investigations.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Austrian Science Foundation FFG and the government of Lower Austria and Upper Austria in the frame of the COMET-program: [grant number CEST SP 190100]. The authors acknowledge the financial support of Project BG 051PO001-3.3.06-0038.