Effect of a nano-structured zirconium coating on the mechanical performance of clinched steel–aluminum joints

Abstract This study investigates the effect of a nano-structured zirconium-based conversion coating on the mechanical performance and corrosion behavior of clinched joints between SAE1006 steel and AA3004 aluminum sheets. Clinching is a mechanical joining process based on localized plastic deformation that enables the joining of dissimilar sheet metals without additional elements or thermal input, making it attractive for lightweight structural applications in the automotive and metalworking industries. In this work, sheets with and without zirconium-based nano-ceramic coating were joined by clinching and comparatively evaluated. The joints were characterized through force–displacement analysis during the joining process, shear strength testing, microhardness measurements, and microstructural analysis using optical microscopy, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and atomic force microscopy (AFM). Accelerated corrosion tests in a saturated humidity chamber were also performed to qualitatively assess corrosion resistance. The results showed that the nano-structured coating significantly modified the surface topography of the sheets, increasing surface roughness and altering the interfacial conditions established during clinching. As a consequence, the coated joints exhibited an average increase of approximately 68% in shear strength compared with uncoated joints, without requiring higher joining forces. In addition, the zirconium-based coating demonstrated effective corrosion protection under accelerated humidity exposure. These findings suggest that nano-structured zirconium conversion coatings can improve both the mechanical performance and corrosion resistance of clinched joints. The results also indicate that surface modifications introduced by the coating may contribute to enhanced joint performance without requiring changes to the clinching process itself.