What Does
Lamellar Corrosion Mean?
This is a type of corrosion that proceeds from initiation sites along planes parallel to the surface. This happens at the grain boundaries and forms products of corrosion, which in turn force the metal from the material body, giving the metal a layered appearance.
This can also be described as intergranular corrosion that is associated with the extruded alloys of aluminum. The most susceptible alloys are cold-worked aluminum alloys which contain zinc, magnesium or copper alloying constituents.
Lamellar corrosion can also be referred to as layer corrosion or exfoliation corrosion.
Corrosionpedia Explains Lamellar Corrosion
Aluminum that has been extruded or rolled may have flattened and arranged parallel grains. Sheet-like layers are formed where corrosion starts at the edges. Corrosion is more vigorous at the edges, and the propagation is along the grain boundaries or at the planes of the insoluble constituents. This corrosion is parallel to the metal surface where the products of corrosion cause a swell in the metal. This enlarges with time as more metal corrodes.
Other characteristics include rapid wear in acidic environments, resistance of the corrosion by some of the aluminum alloys and the accelerated tests which may not predict the long-term behavior of lamellar corrosion. Lamellar corrosion affects aluminum alloys and attacks, proceeding from the sites of initiation on the metal surface.
Lamellar corrosion in ferrous alloys is associated with the excessive internal growth of the metal oxide. This oxide can sometimes exceed that of steel by seven times and this elevates temperatures as well as exfoliating the material damage of the turbines. This exfoliation occurs mostly in ferrite materials when there is an occurrence of multilayer growth. The temperature cycles induce stresses, although thermal expansion between the tube and the scale can also induce stress. This corrosion can also occur in the austenitic stainless steels as a result of the thermal expansion difference between the oxide and the metal. Some of preventive measures include the selection and use of stabilized materials and heat treatment control to avoid temperature range.