Experimental investigation on optimal anodising parameters of nanopore preparation process on the stainless steel surface

The optimisation process of the orthogonal experiment was designed by Taguchi experiment. Nanopores structure was prepared on the surface of stainless steel by anodic oxidation in the nitric acid solution containing sodium chloride and thiourea, and the nanopores were expanded in the solution containing sodium chloride, hydrochloric acid and sulfuric acid. The range and variance analysis results demonstrated that when the anodising process parameters were nitric acid concentration 90 mL L-1, thiourea concentration 3.5 g L-1, sodium chloride concentration 20 g L-1, oxidation time 120 s, oxidation voltage 5.0 V, and expanding time 50 s, a nanopore structure with an average porosity of 36.75% was prepared stably on the surface of stainless steel. Using the bonding strength of polymer-metal assembly as a testing index, the stably and repeatability of the optimal process parameters were verified by injection moulding and tensile tests.