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

• The effects of copper and aminosilane additives on the formation mechanism and structural characteristics of Zr-based conversion coatings (ZrCC) were investigated. • The in-situ analysis of the formation process of ZrCC explained the effect of additives on the interfacial morphology between the conversion coatings and the substrate. • Multi-scale characterization has revealed the electronic interactions among various species within the hybrid ZrCC, contributing to the reduction of dehydration-induced cracking. 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 Cu 2+ , 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.