Investigating the formation mechanism of hybrid Zr-based conversion coatings incorporating copper and aminosilane additives

Abstract

This study focuses on investigating the growth mechanism of hybrid Zr-based conversion coatings (ZrCC) incorporating copper and aminosilane additives, with the objective of revealing the relationship between their microstructural and macroscopic properties. The electrochemical current noise (ECN) analyses in-situ the promoting effect of copper and aminosilane on the uniform corrosion behavior of the substrate during deposition, as well as to validates their influence on the interfacial morphology between the ZrCC and the substrate. The obtained results indicate that the synergistic effect of copper and aminosilane additives effectively reduces the reduction rate of Cu2+, suppresses the occurrence of localized corrosion, and contributes to maintaining a smooth interface between the substrate and the ZrCC. Furthermore, X-ray photoelectron spectroscopy (XPS) and UV–vis DRS provides evidence for the electronic interaction between copper and zirconium oxide species within the conversion coating. The thermal aging resistance of ZrCC is characterized using scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and X-ray fluorescence (XRF) with the aim to evaluate the impact of the industrial electro-coating curing process on the structure of the coating. The results demonstrate that the electronic interactions among different species within the hybrid ZrCC plays a crucial role in mitigating dehydration-induced cracking.