Abstract:The corrosion behaviors of Al Mg alloy LF6M plates(5xxx series) exposed to seawater are significantly different. These alloy plates with different precipitate distribution states had been full immersed in Qingdao, Xiamen and Yulin sea areas for 1, 2, 4 and 8 a respectively, and then were heat treated and probed by SEM and TEM before they were put into the seawater again. The experimental results showed that the intergranular corrosion morphology occurring on the corrosion specimens are well related to the states and sorts of the precipitates and the inclusions located at the grain boundaries, especially chain distributed (MnFe)Al₆ and silicates produced by special heat treatment. The electrochemical measurement of the specimens also gave reasonable explanations for the difference of their corrosion behaviors.

Key words: Al Mg alloy seawater corrosion resistance precipitate