In the present study, effect of carbon nanotubes (CNTs), as electrolyte additives in the micro arc oxidation (MAO) process, on surface morphology of commercially pure titanium (Cp-Ti) was investigated. MAO process was carried out under constant bipolar voltage pulses using two different positive and negative voltage combinations. Results showed that CNTs were successfully incorporated into the coating surface especially within the pores generated by the discharge channels during the MAO process as confirmed by SEM examinations. As the applied voltage and CNTs concentration in the electrolyte were increased, size of micro pores on the surface also increased and their numbers decreased. Higher amount of CNTs addition in the electrolyte resulted in a corresponding decrement in the coating thickness after the MAO process. (C) 2013 Elsevier B.V. All rights reserved.