Corrosion Behavior of Cast and Spray Formed ZA35-3.5Mn Alloys in Boiling Water

The ZA35-3.5Mn alloys were produced by means of spray forming technology and common casting method.Boiling water corrosion behavior of the alloys was studied.The results indicate that the corrosion dynamic curve of spray formed alloy was accordant with the parabolic curve with a rate parameter of 2.14×10-3 mg2·cm-4·s-1,and the corrosion rate was remarkably slower than that of cast alloy whose curve was accordant with linear dynamics.MnO phase was found in the corroded product of cast alloy but not found in spray formed alloy.The MnAl6 phase was at grain boundaries of the cast alloy,η phase and MnAl6 were the cathodes,α-phase had the priority for anodic dissolution.Microstructure of the spray formed alloy was homogeneous and the grains were refined,MnAl6 phase was found.As the anode,the α-phase in spray formed alloy was dissolved,good anti-corrosion performance could be mainly attributed to the barrier effect of corroded product Al(OH)3 against the diffusion of corrosive media.