Corrosion behaviour after anodising of prenitrided CP-Ti

This study presents corrosion characterisation of CP-Ti after nitriding, anodising and duplex surface treatment. The structural properties and corrosion characteristics were investigated by using scanning electron microscopy, X-ray diffraction, Raman spectroscopy and electrochemical polarisation unit. After anodisation and duplex treatment, the porous oxide layer including anatase phase and unshaped or circular pores formed on CP-Ti surface. Size and shape of the pores were changed according to the anodising parameters. It was observed a double layered structure including porous layer on the top and a dense columnar layer beneath that section formed on duplex treated CP-Ti surface at low temperature of anodisation process. Pitting corrosion was observed on all of the samples after the electrochemical polarisation tests. Dense columnar microstructure provided good corrosion resistance via acting as a barrier. As a result, double oxide layer provided an important improvement in corrosion resistance in contrast with nitriding and anodisation processes. © 2011 Institute of Materials, Minerals and Mining.