Corrosion behavior of the nickel/nickel interface during the copper‐sacrificial layer release process in micro‐electroforming

Abstract

This study investigates the corrosion behavior of the nickel/nickel (Ni/Ni) interface during the release of the copper-sacrificial layer in multilayered micro-electroforming. By altering the pre-and posttreatment of multilayered micro-electroforming (degreasing, in situ anodic treatment, pickling, repassivation, and heat treatment), six different types of Ni/Ni interfaces were obtained. The activities and surface characteristics of the pretreated Ni substrates were investigated via open circuit potential and X-ray photoelectron spectroscopy. The microstructures of the as-prepared Ni/Ni interfaces were determined using scanning electron microscopy; after releasing the sacrificial layer in the ferric chloride solution, their corrosion morphologies and corrosion depths were observed under a three-dimensional microscope with an ultra-depth of field. The Ni/Ni interface showed a pre-existing passive layer and interfacial defects. The interface was more prone to attack than the Ni base. Pitting corrosion along the interface boundary occurs via three main processes-initiation, growth, and pit coalescence-with a corresponding reduction in the interfacial adhesion strength and ultimately the structural integrity. The combination of substrate modification (degreasing and pickling) and heat posttreatment effectively avoids localized corrosion. We believe that the surface activation and thermally induced diffusion have worked.

Wire Electrochemical Etching of Superhydrophobic Nickel Surfaces with Enhanced Corrosion Protection

“…Although nickel can be used as a protective metal, its corrosion protection is limited. If an object made of nickel or containing a part with nickel as the outer protective layer is exposed to the natural environment for a long time, its surface often comes into contact with water, which can still cause surface corrosion and cause parts to fail [7]. Therefore, methods of improving the corrosion protection of nickel surfaces in natural environments have attracted widespread attention from researchers.…”