TITANIUM: A PRECIOUS RESOURCE FOR CULTURAL HERITAGE

In this article we are going to examine the reason why titanium today is both one of the most used metals in engineering and electronics, but also an excellent solution in the restoration and science of Cultural Heritage. 

Titanium belongs to the block d, period 4, IV group of the periodic table of elements, with atomic number 22, the titanium was discovered late and valued only in the mid-1900s, due to the high costs of use and the difficulty of moulding it. 

This precious metal is extracted from minerals such as ilmenite (from the Ilmen mountains in Russia) and rutile, present in tonnes in Liguria, in the area of Monte Tarinè, the largest deposit in Western Europe. 

Why it is so extraordinary?

Among the most appreciated mechanical features in structural interventions and in the consolidation of statues and lithic elements there are the corrosion stability and the low thermal expansion, similar to that of the masonry. Indeed, metals have usually a coefficient of thermal expansion higher than traditional masonry. if this factor not properly calculated, can generate tensions and fractures. Moreover, titanium, thanks to its excellent corrosion resistance, also to salt water, does not stain and does not generate dripping on the stones. It is often used in combination with other elements, such as zinc, in order to obtain good passivation. Indeed, titanium-based alloys have recently great importance thanks to their strength and lightness. Another advantage of titanium is its use as a photocatalyst, that allow to degrade pollutants using UV radiation. This property come from the nature of the titanium oxide as semiconductor. Semiconductors are able to promote an electron from the valence band to the conduction band with superior energy, absorbing a photon. This promotion generates an electron-hole pair, which interacts with the chemical species adsorbed on the surface of the material, triggering oxidation and reduction reactions. In this regard, special building materials have been developed (photocatalytic cements) containing a coating of TiO2 against pollution caused by the oxides of nitrogen and sulphur, present in urban areas. 

Another application of this element in Cultural Heritage is as a synthetic mineral inorganic white pigment, replacing the old lead-based one. Titanium White (or titanium dioxide), available since 1920, is chemically inert and has a high stability to light, temperature and humidity. It can be used in all techniques, but is recommended to mix it with other pigments, such as zinc white, using oil binder to favours its siccative properties. A particularly positive feature is that, despite being a white, it has a very high covering power and remains opaque. 

Finally, its antibacterial and hypoallergenic properties are essential for biomedical use, as well as its biocompatibility. In fact, titanium doesn’t release toxic elementsand for this reason is a very valid material for the conservation and respect of pieces of art and the environment.

https://www.britannica.com/science/titanium

Martina