Unprotected iron parts soon become coated with red-brown rust. If this occurs across the entire surface at more or less the same speed, experts refer to this as surface corrosion. In the process the material is eroded practically evenly. (fig. 1)
Surface corrosion is regarded by experts as the “nicest form” of corrosion, as it is calculable. The rate of erosion is known for many corrosion systems. The average progression of corrosion for components – and therefore their lifetime – can therefore be estimated. An example: up to 200 µm of non-alloyed steel is eroded annually in salty sea air, corresponding to a mass loss of 1 g steel/m² per year.