Titanium is a highly corrosion-resistant metal. According to the thermodynamic data of titanium, it is thermodynamically unstable. If titanium dissolves to form Ti2+, its standard electrode potential is highly negative (-1.63V), and its surface is always covered by a passive oxide film. As a result, the stable potential of titanium is shifted towards positive values. For example, in seawater at 25°C, the stable potential of titanium is approximately +0.09V. Chemical handbooks and textbooks provide a range of standard electrode potentials corresponding to titanium electrode reactions. It's important to note that these data are not directly measured and are typically calculated from thermodynamic data. Different sources may represent several different electrode reactions, resulting in variations in the reported data.
The electrode potential data of titanium indicates that its surface is highly active and typically covered by a naturally formed oxide film. Therefore, the excellent corrosion resistance of titanium arises from the presence of a stable oxide film with good adhesion and protective properties on its surface. The stability of this natural oxide film determines the corrosion resistance of titanium. Titanium and titanium alloys, including titanium rods, wires, and sheets, exhibit strong corrosion resistance. However, the corrosion resistance may vary among different grades, as mentioned in our previous website content.
In theory, the P/B ratio of a protective oxide film must be greater than 1. If it is less than 1, the oxide film cannot fully cover the metal surface, thus failing to provide protection. If the ratio is too high, the compressive stress within the oxide film increases, making it prone to cracking and losing its protective effect. The P/B ratio of titanium depends on the composition and structure of the oxide film and typically falls between 1 and 2.5. From this basic standpoint, titanium oxide films can possess better protective properties.
When the surface of titanium is exposed to the atmosphere or an aqueous solution, a new oxide film immediately forms. For example, at room temperature, the oxide film in the atmosphere has a thickness of 1.2-1.6 nm and gradually thickens over time. After 70 days, it naturally thickens to 5 nm. After 545 days, it gradually increases to 8-9 nm. Artificially enhancing oxidation conditions (such as heating, using oxidizing agents, or performing anodization) can accelerate the growth of the surface oxide film, resulting in a relatively thick oxide film and improved corrosion resistance of titanium. Thus, anodized and thermally oxidized oxide films significantly enhance the corrosion resistance of titanium. Our customers have used our titanium rods and wires to create numerous similar products, confirming this direction.
The oxide film of titanium (including thermally formed and anodized films) is typically not a single structure, and its composition and structure vary with the formation conditions.
titanium bar
titanium fiber
titanium electrode plate
