Activation Processes for Electrodeposition on Passive Nickel Surfaces

Abstract

Electrodeposited layer systems consisting of nickel and chromium are commonly used for decorative applications and to protect components against corrosion. Sometimes, already deposited chromium layers have to stripped again to do rework on technical parts. As a result passive layers can form at the surface of the nickel layer. This often leads to poor adhesion of subsequent layers. To prevent such adhesion problems nickel layers have to be activated to allow subsequent deposition of chromium. The thickness of the passive layers depends on the current density and treatment time during chromium stripping, as well as on the properties of the chromium layer to be removed. In summary, process fluctuations in all steps lead to an impairment of the activation effect and thus to adhesion problems.This work will discuss recent results from a project within the framework of the Central Innovation Program for SMEs (ZIM) of the AiF. The aim of the project is to optimize the electrolyte composition and the individual treatment stages. Furthermore, the focus is on establishing measuring techniques for the various process parameters and developing a process model for the implementation of a controlled activation process in a large-scale plant. To achieve these ambitious goals, different parameter settings such as current density and treatment time were studied during the activation process and the effect of these parameters on the subsequent nickel and chromium deposition was evaluated.