The Characters of Titanium Metal

The Characters of Titanium Metal

Titanium and titanium alloys are attractive metallic materials widely used as implants for dental, restorations, and orthodontic wires, as well as orthopedic due to their excellent corrosion resistance and biocompatibility. Titanium and its alloys present a high corrosion resistance even in very aggressive environments containing strong acidic electrolytes. This aspect is related to their inherent nature to form spontaneously dense barrier-type titanium dioxide (TiO2), which is chemically very stable and increases greatly by anodic oxidation.

The good mechanical resistance/density ratio presented by Ti and its alloys make them useful candidate materials in the aerospace, aeronautic and naval industries. In the majority of solutions and like other valve metals, Ti is in the passive state at open-circuit potential, where the thickness of its naturally formed oxide film increases linearly with time before the attainment of the steady state value.

Titanium is highly resistant to corrosion in a wide range of environments conferred by the naturally formed passive film on the surface. However, as pH decreases and temperature increases, titanium passivity decreases resulting in decreasing corrosion resistance, especially crevice corrosion resistance. One of the most effective strategies for enhancing the corrosion resistance, especially in a reducing acidic environment such as the crevice region, is through alloying with platinum group metals (platinum, palladium, rhodium, ruthenium, iridium, and osmium). Among the platinum group metals, platinum and ruthenium are commonly used as the alloying elements. It is generally accepted that the function of these noble metal elements is to create cathodic sites, which catalyze proton reduction in the reducing acidic environment. This catalysis of proton reduction shifts the corrosion potential into the passive region, thereby enhancing the corrosion resistance.