Sample preparation of anodised aluminium oxide coatings for scanning electron microscopy

•Anodised aluminium oxide coating samples were prepared for SEM examination.•Three preparation methods were trialled to assess coating thickness and structure.•Cryogenic fracturing was found to be destructive to samples.•Mechanical fracturing provided relatively accurate coating thickness measurements.•Coating structure could only be evaluated from mechanically fractured samples. Characterisation of anodic aluminium oxide coatings and measurement of their thickness using microscopic techniques is valuable for analysing the effectiveness of the prior anodising process. Three different methods for preparing samples to view the coating cross-section (mechanical fracturing, cryogenic fracturing and metallography) were trialled and assessed for speed of implementation, simplicity and achievable measurement accuracy. Cryogenic fracturing was found to be destructive to samples. Mechanical fracturing yielded relatively accurate coating thickness measurements and coating structural information. Metallography provided the most accurate coating thickness measurement at the expense of coating structural information.