Influencing of Temperature on Plating Microstructure of Galvalume Sheet Steel

The change of plating microstructure was investigated by microscope and SEM,when the Galvalume sheet steel was tested in diverse high temperatures.It was showed the color of surface didn't change when temperature was in 300~450℃,but the Galvalume branching crystal cracks expanded larger and larger,as the temperature was higher.The Al-Si-Fe alloy stratum was formed and it's distribution developed from intermittence to continuum,it's thickness was increasing,So that plating cracking and desquamating with base sheet steel,the corrosion resistance decreased.The plating was all alloyed and oxide to change color quickly when temperature was in 500,it complete lost corrosion resistance in the end.