Process Modeling and Intuitive Search Based Optimization of Average Surface Roughness in Citrate Stabilized Electroless Nickel-Boron Coatings

The present study aims to replace the hazardous thallium- or lead-based additive with trisodium citrate as an alternative eco-friendly stabilizer in electroless nickel boron deposition. Also, the effect of input process parameters on average surface roughness ( R a ) was screened using a Plackett–Burman design (PBD). The PBD revealed that nickel chloride, sodium borohydride, and trisodium citrate concentrations were the significant variables. These variables are then optimized using a Box–Behnken design, simulated annealing and genetic algorithm (GA) techniques. Among the three techniques, the lowest R a value was observed using the GA technique and hence the process parameter values from GA were varied individually and simultaneously using the intuitive search algorithm to further converge on the R a value. The effectiveness of the search was validated by performing experiments in triplicate and an R a of 0.252 ± 0.004 µm was obtained. Deposit characterization was performed for surface morphology and to identify the phase structure of the coating.