It is generally used when hot-dip galvanising is not possible because the fabrications are too complex or may distort. This is because large fabrications that are hot dipped are often too big for the dipping tanks, so are dipped and turned over and dipped again. The galvanising dipping tank is around 450°C and the part not submerged acts as a radiator and the difference in heat can put large stresses through the material often causing permanent distortion.
As in the case of Aluminium welding of like metals, to prevent stress corrosion cracking. This treatment is specified by Network Rail, the Highways Agency and the Water Authorities as the base layer for further paint coats, particularly on immersed fabrications.
Thermal spray coating is ideal for smaller and intricate parts as well as large fabrications and structures and can act as a replacement for galvanizing, specifically in the form of hot zinc spraying. It is often used on very large bridge structures and lighting columns for the Highways Agency. Application is done in accordance with ISO 22093.