Surface preparation and corrosion behavior of titanium alloys were studied; both topics deal with the formation of surface oxide films. When metals are prepared for surgical implant use, an effort is made to produce an optimum surface. Effects of the surface treatments on surface morphology, surface film composition, and structure are shown in transmission electron photomicrographs and electron diffraction patterns. Roughened surfaces were produced, and surface films of titanium oxide (TiO) or titanium dioxide (TiO2) or both occurred on some specimens. Sodium titanate (NaO · xTiO2) occurred on the specimens washed in sodium hydroxide (NaOH) solution. Open circuit potential versus time curves have been measured to show some electrochemical effects of various surface treatments. The results show that titanium alloys immersed in Hanks' physiological solution reach the same final open-circuit potential after approximately two weeks' exposure regardless of prior surface treatment. Measurements of the anodic polarization behavior of titanium alloys and other surgical implant alloys show the effects of alloy composition and the testing solution on the passive region and breakdown potentials of these materials. In general, for titanium alloys, the differences are not great, but the presence of nickel results in a significant lowering of the breakdown potential. The materials studied were titanium, Ti-6Al-4V, titanium-nickel (memory alloy), Ti-13Cu-4Ni, and Ti-4.5Al-5Mo-1.5Cr. In all cases titanium materials are more corrosion resistant in Hanks' solution than cobalt-chromium-molybdenum Type 316L stainless steel, or cobalt-nickel-chromium alloys. Repassivation measurements show the rapid formation and the high degree of stability of the protective film on titanium and titanium alloys.

Section 514 of the Food, Drug, and Cosmetic Act requires performance standards to assure reasonable safety and effectiveness. Although the procedures appear to be complex and lengthy, they are comparable to those established by national and international standards organizations. Persons most directly affected by the standard may participate in both the performance standard development and the establishment of a final regulation on the performance standard. As a part of due process, those most affected have the opportunity to request a review of any matter by an advisory committee of experts. A key element in the performance standard development procedure is the establishment of a statement of the risks associated with the use of the device and intended to be controlled by a performance standard. For vascular graft prosthesis with diameters of 6 mm and greater, the establishment of the device risks and methods of control will be the basis from which the development of a performance standard can proceed. The objective is to select a set of risks and methods of control so that the standards development procedure is manageable and results in an effective performance standard.

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The influence of small variations in the composition on the corrosion behavior of Co-Cr-Mo alloys has been studied using scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDX), and electrochemical measurements. SEM and EDX data were correlated with data from in vitro corrosion measurements involving repassivation and also potentiostatic anodic polarization measurements. Specimens studied included the four alloys shown in Table 1. Corrosion tests were conducted in Hanks' physiological saline solution which has a pH of 7.4 and was held at a temperature of 37°C. Specimens were mechanically polished to a surface finish with 0.05 µm A1203, then exposed to the solution and anodically polarized at a rate of 0.006 v/min. All voltages were measured vs. the saturated calomel electrode (s.c.e.).. Specimens had breakdown potentials near 0.47V vs. s.c.e.