Modern coil coating processes/Future developments in corrosion protection

摘要

Pre-coated sheet steel and aluminium are used in a wide variety of applications ranging from facade construction to brown and white goods and ship containers. At the same time, the battle against rust still constitutes a special challenge for researchers and developers in the field of coil coating technology, as special corrosion protection demands are made of the coated panels. Depending on the intended use, the metal must be able to withstand considerable corrosive attack, as in the construction sector for example. For most industry sectors the bottom line is that corrosion must not occur, even if the material is constantly exposed to weathering and acid rain. For decades it was always possible to rely on a universal remedy to prevent corrosion: chromate. This chromium/oxygen compound seemed to be an almost ideal substance for researchers and developers. On account of its favourable position in the electrochemical series, it was the perfect partner for the protection of iron, zinc and aluminium, which are the chief engineering metals in coil coating. Chromate was either mixed directly into the paint as an anti-corrosive pigment or was applied to panels by yellow chromating in a pre-treatment process before paint application.