Filiform corrosion is a particular problem for coated aluminum and low-alloy steel structures. The corrosion is initiated by the combined action of water, oxygen and starter salts. Beginning from bare edges or local damages to the coating, the corrosion proceeds between the coating and metal substrate in the form of thread-like filaments.
The development of coating systems with improved corrosion protection as well as the coating quality control require the evaluation of a large numbers of coated test plates. To perform the accelerated corrosion, the coating is first damaged by a standardized procedure of scribing a defined pattern. Then the test plates are exposed to different corrosive atmospheres in climate chambers. After a predefined number of hours, the extent of corrosion is measured. Traditionally this is done manually, using a magnifying glass with integrated scale, making the process tedious, time-consuming, error-prone and highly subjective.