锌铝镁镀层于3.5%NaCl溶液中腐蚀行为的研究

使用扫描电镜及扫描探针分析了锌铝镁镀层的表面形貌及成分,使用X射线光电子能谱仪及电化学技术分析了锌铝镁镀层腐蚀产物的化学组成、电化学性能,对锌铝镁镀层的耐蚀机制进行了探讨,结果表明:锌铝镁镀层主要由初生锌相、富铝相及共晶组织组成,Mg元素主要分布于共晶组织中。在3.5%NaCl介质腐蚀过程中,锌镀层腐蚀产物主要由Zn₅(CO₃)₂(OH)₆及ZnO组成,锌铝镁镀层腐蚀产物主要由Mg(OH)₂、4MgCO₃·Mg(OH)₂及Zn₅(CO₃)₂(OH)₆组成。锌镀层腐蚀产物电荷传输电阻逐渐降低,而锌铝镁镀层腐蚀产物电荷传输电阻逐渐增大,且后者大于前者。即锌镀层腐蚀产物无法抑制镀层的腐蚀,而锌铝镁镀层腐蚀产物则可以对镀层电化学反应起到抑制作用,对镀层提供一定程度的保护。

Study on Corrosion Behavior of Zn-Al-Mg Coating in 3.5%NaCl Solution

In this paper, scanning electron microscopy and scanning probe are used to analyze the surface morphology and composition of the Zn-Al-Mg coating. X-ray photoelectron spectrometer and electrochemical technology are used to analyze the chemical composition and electrochemical property of the corrosion products on Zn-Al-Mg coating. The corrosion mechanism of Zn-Al-Mg coating are discussed. The conclusions are as follows: Zn-Al-Mg coating is mainly composed of primary phase, aluminium rich phase and eutectic composition. Mg elements are mainly distributed in the eutectic organization. In the process of corrosion, the corrosion products on Zn coating are mainly composed of Zn₅(CO₃)₂(OH)₆ and ZnO, and the corrosion products on Zn-Al-Mg coating are mainly composed of Mg(OH)₂,4MgCO₃·Mg(OH)₂ and Zn₅(CO₃)₂(OH)₆. The charge transfer resistance of corrosion products on Zn coating is gradually reduced while the charge transfer resistance of the corrosion products on Zn-Al-Mg coating is gradually increased, and the latter is greater than the former. The corrosion products of zinc coating can not inhibit the corrosion of the coating while the corrosion products of zinc aluminum and magnesium can inhibit the electrochemical reaction of the coating and provide corrosion protection to the coating.