Anodic polarization measurements made in Hanks' physiological solution at 37 degrees C and a pH of 7.4 show titanium materials to be the most passive of the following metals: titanium, Ti-6A1-4V, Ti-Ni (memory alloy), MP35N (Co-Ni-Cr-Mo), Co-Cr-Mo, 316L stainless steel, and nickel. The influence of the amino acids, cysteine, and tryptophan on the corrosion behavior of Ti-Ni and Ti-6A1-4V was studied. Cysteine caused a lower breakdown potential for Ti-Ni, but it did not affect the breakdown of Ti-6A1-4V, although an increase in current density for Ti-6A1-4V was observed. Tryptophan produced no significant effects.

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Controlling N2 binding at transition-metal centers is essential in facilitating its rapid functionalization. Herein, we report the synthesis of high-spin four-coordinate Co–N2 complexes bound by our recently developed class of N,N,C heteroscorpionate ligands. End-on bridging and terminal binding modes for Co-bound N2 are both readily accessed by adjusting the steric profile of the supporting ligand. In the reported complexes, N2 is only weakly bound and is reversibly lost upon application of vacuum or an Ar atmosphere, with concomitant formation of an unusual Co–C–Si 3-center–2e– interaction. This work further demonstrates the power of steric control in modulating small-molecule binding at low valent centers.

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.