be reached without any seizing with a coefficient of friction equal to 0 15 in other words experimental results yielded the surprising conclusion that acceptable although not optimum results may be obtained even if treatment parameters vary from the preferable values either intentionally or accidentally the critical factor in producing an adherent titanium oxide friction layer appears to be a constantly decreasing quantity of available oxygen during treatment at least where the constantly decreasing amount becomes within preferred initial parameters during the treatment a ring made of titanium or titanium alloy having a diameter of 35 mm and a height of 20 mm and a speed of rotation of 1200 r p m rubs on a steel plate in the shape of a parallelopiped the dimensions of which are 30 u00d7 18 u00d7 8 mm an increasing lead varying from 0 to 600 dan within 3 min 20 sec is applied to the plate after the maximal load of 600 dan is reached the test is carried on at said maximum load the test is effected in pure and neutral vaseline oil a ring of titanium or titanium alloy treated by the conventional treatment of anodic oxidation mentioned hereinabove seizes as soon as the load reached 80 dan in contrast a ring treated by the method according to the invention as explained in example 1 650 u00b0 c 8 h 1 29 mg cm 2 may reach the load of 600 dan and rotate for 2 hours under said.