Simulating study of atmospheric corrosion of Zn-Al alloy coating in industrial zone: Structure and properties of zinc hydroxysulfate rust particles prepared in the presence of Al(III)

Abstract In order to simulate the atmospheric corrosion of Zn-Al alloy coating on the steels in industrial zone, zinc hydroxysulfate (Zn 4 (OH) 6 (SO 4 )· n H 2 O: ZHS) rust was artificially synthesized by hydrolyzing the ZnO particles in a mixture of aqueous ZnSO 4 and Al 2 (SO 4 ) 3 solutions and the structure and properties of the products were examined by various means. Then, the atomic ratio X Al  = Al(III)/(Zn(II) + Al(III)) in the solution was ranged from 0 to 1.0. Adding Al(III) decreased the solution pH before aging to inhibit rust formation. Added Al(III) was easily incorporated in the particles than Zn(II). Increasing X Al turned the major rust following as hexagonal plate-like ZHS particles → hexagonal plate-like Zn-Al layered double hydroxide (LDH) particles → cubic Al 6 O 5 (SO 4 ) 4 ·H 2 O particles. These rust particles possessed a high adsorption affinity to corrosive CO 2 gas. From these results, it can be supposed that atmospheric corrosion of Zn-Al alloy coating on the steels in industrial district produces the dense and compact rust layer composed of plate-like ZHS and/or Zn-Al-LDH particles owing to their preferred orientation to suppress further corrosion of steels.