Investigation of the electrolytic corrosion in steel roof tiles coated with zincalume

ABSTRACT The steel roof tiles used in farm sheds are vulnerable to the action of weathering. The corrosion arises due to difference of electrical potential between the metallic surface and the environment, leading to an electrical load of this surface. They need a protection, an anticorrosive coating, whose purpose is to increase the lifetime. Zincalume is a kind of coating currently used to decrease the effects of sun and rain in the metal roof tiles. This coating consists of an alloy of zinc and aluminum. The Zincalume coating allows the combination of zinc and aluminum by combining the barrier resistance offered by the first one and the good performance of the second one in protecting edges and small discontinuities. This product maintains the structural strength of the steel base and provides high resistance to atmospheric corrosion leading to the interruption of the electrical current. The degradation of steel roofing coated with a layer of zincalume subject to weathering was analyzed in this work. Analysis with X-ray fluorescence was used to verify the chemical composition of the studied samples. Macrographic and micrographic analyzes were also carried out in order to evaluate the degradation of the roof tiles.