Influence of pulse parameters on electrocodeposition of Cr–Al₂O₃ nanocomposite coatings from trivalent chromium bath

Abstract

Cr and Cr–Al₂O₃ coatings were electrodeposited from Cr(III) bath with both pulsating and direct current onto copper substrates. Pulsating current resulted in homogeneous films of higher Al₂O₃ content and lower particle agglomeration than the direct current. Differences were more tangible at shorter duty cycles and pulse frequencies. Pulsating current improved both microhardness and corrosion resistance. The presence of alumina nanoparticles resulted in greater current efficiency, higher film microhardness and better corrosion resistance. Maximum current efficiency, highest microhardness and densest electrodeposited coatings were achieved at current density of 20 A dm⁻², duty cycle of 40% and pulse frequency of 10 Hz.

Keywords:

• Nanocomposites
• Pulse plating
• Trivalent chromium
• Codeposition
• Corrosion resistant
• Microhardness