Growth of anodic oxide films on AC2A alloy in sulphuric acid solution

Growth behaviour of anodic oxide films on AC2A Al cast alloy was investigated in sulphuric acid solution using SEM, optical microscope (OM) and confocal scanning laser microscope (CSLM) and energy dispersive spectroscopy (EDS). The AC2A alloy contains three different types of second-phase particles: Al–Cu, Al–Cu–Fe–Si and Al–Si particles. The growth of anodic oxide films was critically retarded by the presence of non-reactive particles of Al–Si, while little effect was observed by the presence of active particles of Al–Cu and Al–Cu–Fe–Si. The most severe retardation effect on the growth of anodic films on AC2A alloy resulted from agglomerated Al–Si particles.

Research highlights
► Effects of second-phase particles on the growth of anodic oxide films.
► Dissolution of Al–Cu and Al–Cu–Fe–Si during anodizing and their little contribution to the non-uniform growth of anodic oxide films.
► Al–Si particles were not dissolved during anodizing.
► Non-uniform growth of anodic oxide films is due to the presence of Al–Si particles.