Effect of Electroless Nickel Pre-plating Time on Properties of Electroless Nickel on Aluminum

Objective To reveal the variation trend of surface morphology of the sample along with the different pre-plating time and discuss the correlations between surface morphology,adhesion of coatings with aluminum matrix,and corrosion resistance.Methods Electroless nickel coatings were prepared by chemical deposition at different pre-plating time. The surface morphology of coatings was characterized by SEM. The adhesion of coatings with aluminum matrix was determined and evaluated by bending test,thermal shock test and scribe test. And the corrosion resistance of coatings in a simulated fuel cell corrosion medium was also characterized by the electrochemical workstation. Results With the electroless nickel pre-plating time increasing,the surface morphology of pre-plating nickel coating gradually became dense and uniform. And the particle size of pre-plating coating became bigger. Electroless nickel coating first became smooth and then rough,and its corrosion resistance and adhesion with matrix also first increased and then decreased with the electroless nickel pre-plating time increasing. Conclusion The best surface morphology,corrosion resistance and the maximum adhesion of the coating was obtained at 5 min of electroless nickel pre-plating time.