The techniques of single and double layers of implanted Xe ions marker as well as the O18 tracing method are used to study the mechanism of the anodic oxidation of Ti and TA6V (Ti6A14V). It is observed that in 5 wt% ammonium citrate, the mechanism of the anodic oxidation of Ti is very different from that of TA6V. For Ti, new oxide is formed mainly by the migration of Ti cations to the solution/oxide interface and the regions at which new oxide is formed are at the solution/oxide interface and in the pre-oxide near the interface. While for TA6V, anodic film growth is due to the migration of oxygen anions to the oxide/metal interface and the growth regions of new oxide are at the oxide/metal interface and in the pre-oxide near the interface. Transport numbers for Ti oxidized in 1 wt%. KOH are calculated and found to be affected by oxidation temperature, i.e. at 3'C, the average transport number is 0.32, while at 30&00B0;C,it is 0.28. Current efficiencies are above 99.8%. AES spectra show that the distribution profiles of the elements V and Al in anodic film on TA6V are uniform.