镀层厚度对热纯锌板及热基锌铝镁板抗石击腐蚀性能的影响

Effect of Coating Thickness on Stone Chip Corrosion Resistance of Hot Galvanizing Sheet and Hot-Base Zn-Al-Mg Sheet

采用抗石击试验和中性盐雾试验,对比研究了不同镀层厚度热镀锌(GI)板以及热基锌铝镁(ZM)板的抗石击腐蚀性能。结果表明:ZM板镀层硬度大于GI板镀层,GI试样的石击坑深度均大于50μm,而ZM120和ZM275试样的石击坑深度平均值分别仅为22.1μm、23.0μm;经过1176h中性盐雾试验后,GI275与GI1200石击试样表面红锈面积分别达到50%及10%,ZM120及ZM275石击试样表面无红锈;当镀层厚度相同时,ZM板的耐蚀性明显优于GI板,且同种镀层试样的耐蚀性随镀层厚度增加而提升;ZM板镀层中的Mg可有效缓冲表面薄液膜的pH,降低OH-含量,进而抑制ZnO生成,镀层腐蚀产物主要是致密的Zn5(OH)8Cl_(2)·H_(2)O,可形成物理屏障,并作为电子绝缘体阻止电化学腐蚀反应的进一步进行。

The stone chip resistance test and neutral salt spray test were used to compare the stone chip corrosion resistance of hot-dip galvanized(GI)sheets and hot-base zinc-aluminum-magnesium(ZM)sheets with different coating thicknesses.The results show that the hardness of ZM sheet coating was greater than that of GI sheet coating,and the depth of stone chip pit of GI samples was greater than 50μm,while the average depth of stone chip pit of ZM120 and ZM275 samples was only 22.1μm and 23.0μm,respectively.After 1176 h neutral salt spray test,the red rust area on the surface of GI275 and GI1200 stone samples reached 50%and 10%,respectively,and there was no red rust on the surface of ZM120 and ZM275 stone samples.When the coating thickness was the same,the corrosion resistance of ZM sheet was obviously better than that of GI sheet,and the corrosion resistance of the same coating sheet increased with the increase of coating thickness.The Mg in the ZM sheet coating could effectively buffer the pH of the thin liquid film on the surface,reduce the content of OH^(-),and then inhibit the formation of ZnO.The corrosion products of the coating were mainly dense Zn_(5)(OH)_(8)Cl_(2)·H_(2)O,which could form a physical barrier and act as an electronic insulator to prevent the further electrochemical corrosion reaction.