Titanium and titanium alloys have two excellent characteristics: high specific strength and excellent corrosion resistance. This is also the reason why titanium alloys are preferred in the aerospace industry, chemical industry, medical engineering and leisure industries.

Specific strength and high temperature performance:

The density of metals varies greatly. Lithium has the smallest density at 0.5g/cm-3, while osmium and iridium have the largest density at 22.5g/cm-3. The density of 5g/cm-3 is the dividing point between light metals and heavy metals, so titanium with a density of 4.51g/cm-3 is the heaviest light metal. Although the density of titanium is twice that of aluminum (a typical light metal), its density is only about half that of iron or nickel (Figure 1.1).

Only below 300℃, the specific strength of carbon fiber reinforced plastic is higher than that of titanium alloy (Figure 1.2). At higher temperatures, the specific strength of titanium alloys is particularly excellent. However, the maximum use temperature of titanium is limited by its oxidation characteristics. Because titanium aluminum compounds can partially overcome this shortcoming, they have become the focus of alloy development. Traditional high-temperature titanium alloys can only be used at temperatures slightly higher than 500°C, while titanium-aluminum-based alloys are directly comparable to mature high-temperature steels and nickel-based superalloys (Figure 1.2).

Corrosion resistance:

Titanium and titanium alloys have good corrosion resistance. Except for some examples summarized in the following table, it is important to maintain the integrity of the titanium oxide film on the surface of titanium and ensure its good corrosion resistance; or once the oxide film is damaged, at least there is a chance to get it in a specific environment repair. Therefore, titanium and titanium alloys have long-term corrosion resistance in an oxidizing atmosphere, and the presence of a small amount of oxygen and water is sufficient to form a protective oxide film.

Adding inert metals (usually palladium and ruthenium), nickel and molybdenum or using corrosion inhibitors in the machine can improve the corrosion resistance of titanium. A large number of corrosion databases provide corrosion information of specific alloys in different media.

Titanium is required to have excellent corrosion resistance in coastal/offshore applications. For reasons of mechanics, technology and corrosion, the new generation of offshore platforms have thousands of meters of titanium alloy transmission pipelines and supply pipelines.