Electroplating and characterization of Cr–Al₂O₃ nanocomposite film from a trivalent chromium bath

Abstract

Purpose – The main aim of this study was to improve current efficiency and to obtain thicker coatings via aluminum oxide (Al 2 O 3 ) addition to the chromium (Cr) (III) bath. Design/methodology/approach – Pure Cr and nanocomposite Cr–Al 2 O 3 coatings were electrodeposited from Cr (III) bath onto cathode copper substrates by conventional method. Dependence of current efficiency to current density, Al 2 O 3 content and particle size were investigated. Findings – Current efficiency increased with Al 2 O 3 amount and decreased with Al 2 O 3 particle size. Maximum current efficiency was achieved at 25 A/dm 2 for pure Cr and 30 A/dm 2 for composite coatings. Al 2 O 3 bath content, current density and stirring rate increased the coating Al 2 O 3 weight per cent significantly. Addition of Al3+ bath composition inhibited nanoparticle agglomeration, increasing film homogeneity. Cr–Al 2 O 3 nanocomposites showed higher microhardness and better corrosion resistance than pure Cr layer. Originality/value – Cr (III) is not as toxic and as carcinogenic as Cr (VI) which is widely used for Cr electroplating these days. Low current efficiency and poor product quality are, however, major drawbacks of the former. This paper describes significant improvements obtainable by addition of Al 2 O 3 nanoparticles to the Cr (III) bath for increasing the microhardness, the corrosion resistance and the current efficiency of the deposition.