ANALYSIS OF STEEL CORROSION AND ITS PROTECTION

The phenomenon of corrosion of steel is a natural and artificial phenomenon caused by the use and exploitation of these metals.In the industrial and metallurgical sectors (automotive, construction, etc.), the surface of steel sheets is coated in order to protect them against corrosion attacks that occur, for example, during the storage of sheets or on vehicles (rain, de-icing salts...). On an industrial scale, two processes are mainly used to protect steels from corrosion: galvanization and electro-galvanization. However, the classical methods of protection are not sufficient and the total cost of corrosion reaches today 3 to 4 % of the world GDP...Most often, weaknesses in corrosion resistance are observed on hot-dip galvanized steels when they are stored for long periods in uncontrolled (and often corrosive) conditions. In addition, these steels have poor bonding properties, especially for steels coated with zinc on both sides.Existing coatings on metal surfaces are often insufficient for the protection of critical vehicle parts (doors, side rails, mud flaps...) and cut edges. They must then be completed by post-protections in order to increase the corrosion resistance of the whole.