Characteristics and corrosion resistance of hard-anodised 6061-T6 aluminium alloy

ABSTRACT

Hard anodic coatings were formed on 6061-T6 aluminium alloy samples using direct current. Surface morphology and cross-section of coatings, as well as their hardness and corrosion behaviour, were studied. It was found that decreasing the applied current density from 55 to 35 mA cm⁻² resulted in more uniform coatings with fewer surface defects, lower porosity, and higher hardness values. The optimum electrolyte concentration and hard-anodising time, where less defective coatings were achieved, were found to be 180 g L⁻¹ and 50 min, respectively. The hardness of the optimum film was around 500 HV, and its corrosion current density was 3.2 × 10⁻⁹A cm⁻². All other samples that were produced at different current densities (30-55 mA cm⁻²), times (40-100 min), and electrolyte concentrations (25-220 g L⁻¹) had lower hardness and corrosion resistance than the optimum coating. The polarisation resistance of the optimum coating was about 1100 times higher than the bare substrate.

KEYWORDS:

• Hard-anodising
• aluminium alloy
• SEM
• hardness
• corrosion

Disclosure statement

No potential conflict of interest was reported by the author(s).