Optimization of electroless Ni-B-nanodiamond composite coating corrosion resistance and deposition rate

Electroless nickel boron (Ni-B) is an autocatalytic deposition technique that has been used in various industries because of the unique mechanical properties it confers to substrates. Nevertheless, its undesirable pitting corrosion behavior has limited its applications. One of the methods for improving the corrosion resistance of electroless Ni-B is adding particle to fabricate composite coatings. Among the particles that have been added to the Ni-B electroless bath, carbon allotropes have shown promising behavior due to their ability to act as a strong filler, being inert. However, adding the particles into the electroless Ni-B requires optimization of bath parameters to achieve the desirable properties by avoiding lower deposition rate and agglomeration. This study aims to shed light on the aforementioned problems by optimizing the corrosion resistance and deposition rate of Ni-B-nanodiamond coating by varying the concentration of reducing agent, nanodiamond, and stabilizer as bath variable parameters. To do so an experimental design with 20 experiments and six replications at the center point (using a central composite design) was used. The quadratic model based on RSM methods was found to be appropriate to define the relationship between variables and responses in electroless Ni-B-nanodiamond composite coating optimization. Variation in nanodiamonds concentration shows a profound effect on the coatings polarization resistance and the upper and lower limit for the bath stability have been determined. Based on the results plot of actual and predicted values of corrosion resistance and deposition rate, the model proposed for the corrosion resistance and deposition rate had 92.85% and 98.37% accuracy respectfully.