Synthesis, corrosion, and wear resistance of a black microarc oxidation coating on pure titanium

Black microarc oxidation (MAO) ceramic coatings were prepared on TA2 pure titanium by adding the colorant [Cu(NH3)(4)](2+) to a Na2SiO3 base solution. The microstructures of the MAO coatings were characterized by scanning electron microscopy, energy dispersive X-ray spectrometry, and X-ray photoelectron spectroscopy. The corrosion resistance and wear resistance of the coatings were evaluated through potentiodynamic polarization and friction tests. [Cu(NH3)(4)](2+) was absorbed into the pores of the microarc discharge to form black copper oxide under high temperature and pressure. Cu content in the MAO coating increased with [Cu(NH3)(4)](2+) concentration. The wear resistance and hardness of the prepared black ceramic coatings were remarkably improved in terms of self-sealing microstructure. However, the corrosion resistance of the black coatings was approximately one or two orders of magnitude lower than that of the MAO coating without Cu doping. This study shows that the proposed method is a promising method for preparing decorative coating or absorbing light coating on a titanium surface.