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 (Al₂O₃) addition to the chromium (Cr) (III) bath.

Design/methodology/approach

Pure Cr and nanocomposite Cr–Al₂O₃ coatings were electrodeposited from Cr (III) bath onto cathode copper substrates by conventional method. Dependence of current efficiency to current density, Al₂O₃ content and particle size were investigated.

Findings

Current efficiency increased with Al₂O₃ amount and decreased with Al₂O₃ particle size. Maximum current efficiency was achieved at 25 A/dm₂ for pure Cr and 30 A/dm₂ for composite coatings. Al₂O₃ bath content, current density and stirring rate increased the coating Al₂O₃ weight per cent significantly. Addition of Al3+ bath composition inhibited nanoparticle agglomeration, increasing film homogeneity. Cr–Al₂O₃ 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 Al₂O₃ nanoparticles to the Cr (III) bath for increasing the microhardness, the corrosion resistance and the current efficiency of the deposition.

Citation

Salehi Doolabi, M., Khatiboleslam Sadrnezhaad, S. and Salehi Doolabi, D. (2014), "Electroplating and characterization of Cr–Al₂O₃ nanocomposite film from a trivalent chromium bath", Anti-Corrosion Methods and Materials, Vol. 61 No. 4, pp. 205-214. https://doi.org/10.1108/ACMM-12-2012-1227