THE ATMOSPHERIC CORROSION MECHANISM OF 55-PERCENT-AL-ZN COATING ON STEEL

This paper presents the results of a study aimed at understanding the atmospheric corrosion mechanism of the 55%Al-Zn coating (Galvalume) on steel and a comparison with the behaviour of galvanized sheets (Sendz imir). Research has been carried out in different types of atmosphere in Spain, Brazil and Portugal. Unlike the galvanized coating, which su ffers a generalized attack of its surface, the 55%Al-Zn coating underg oes a localized type of attack which commences in the interdendritic r egions of the material. An analysis is also made of the additional pro tection which may be provided by a chemical passivating treatment appl ied on both types of coating. (C) 1997 Elsevier Science Ltd.