Full Optimization of an Electroless Nickel Solution: Boosting the Performance of Low-Phosphorous Coatings.

Univariate and multivariate optimizations of a novel electroless nickel formulation have been carried out by means of the Taguchi method. From the compositional point of view, adjustment of the complexing agent concentration in solution is crucial for fine-tuning free Ni ions concentration and, in turn, the mechanical properties of the resulting coatings. The Ni (II) concentration and the pH are the main parameters which help restrict the incorporation of phosphorous into the Ni layers. On the other hand, the stirring rate, the pH and the reducing agent concentration are the most influential parameters for the corrosion resistance of the coatings. Multivariate optimization of the electrolyte leads to a set of optimized parameters in which the mechanical properties (hardness and worn volume) of the layers are similar to the optimal values achieved in the univariate optimization, but the corrosion rate is decreased by one order of magnitude.