Effect of NaAlO2 concentrations on the properties of micro-arc oxidation coatings on pure titanium

• The concentration of NaAlO2 has effects on the characteristics and the qualities of the MAO coatings on pure titanium.
• With the NaAlO2 concentration increasing, the working voltage increase and promote the growth rate of MAO coatings.
• The number and size of the sintered disc on MAO coatings increased gradually and the number of micro-pores decreased.
• The content of the TiO2(B) phase decreases as NaAlO2 increases.
• The corrosion rates decreased firstly and eventually increased.

TiO2 coating was deposited on a pure titanium substrate using a micro-arc oxidation (MAO) process in an electrolyte solution with the NaAlO2 addition varying from 0 to 0. 4 g/l. With increasing NaAlO2 concentration, the working voltage could effectively increase and promoted the growth rate of MAO coatings on pure titanium. The X-ray diffraction (XRD) results indicated that MAO coatings mainly consisted of TiO2(B), rutile, and anatase. The surfaces of the MAO coatings which were formed on pure titanium in the electrolyte without NaAlO2 mainly consisted of micro-pores. The number of the sintered disc and the discharge channel diameter increased with increasing NaAlO2 concentration. The corrosion rates of MAO coatings decreased at the first and then increased.