新型达克罗涂层的制备与组织结构  

Preparation and Microstructure of New-type Dacromet Coating

作　　者：邢婉晴 陈文革[1] XING Wan-qing;CHEN Wen-ge(School of Materials Science and Engineering,Xi'an University of Technology,Xi'an 710000,China)

机构地区：[1]西安理工大学材料科学与工程学院,西安710000

出　　处：《表面技术》2022年第12期169-177,共9页Surface Technology

基　　金：西安市创新项目(21XJZZ0042)。

摘　　要：目的制备环保的无铬达克罗涂层,研究涂层烧结和腐蚀前后微观组织结构的变化,探究涂层的防腐机制。方法用锌铝合金粉替代锌铝混合粉,钼酸盐和硅烷偶联剂取代铬酸盐制备无铬达克罗涂料,采用喷涂技术在Q235钢基体上涂装制备涂层。通过X射线衍射仪(XRD)分析涂层在烧结和腐蚀前后的物相组成。通过扫描电子显微镜(SEM)和能谱仪(EDS)分析涂层在烧结和腐蚀前后微观组织形貌的变化。结果钢基体上无铬达克罗涂层组织致密,表面平滑,呈银灰色,无明显孔隙,涂层厚度为8~12μm。涂层烧结前后表面均由富锌α相、富铝η相和Fe相组成,但烧结后物相的结晶程度较高,未有新相产生。涂层与基体结合紧密在于涂层中的Zn和Al与基体中的Fe在结合界面处相互扩散形成冶金结合。在浸泡试验中,锌铝合金粉优先溶解为海绵状组织,随后与腐蚀介质反应生成针状成岛状分布的腐蚀产物,腐蚀产物包括Zn_(5)(OH)_(8)Cl·H_(2)O、Al_(5)Cl_(3)(OH)_(12)·4H_(2)O、Zn_(5)(OH)_(6)(CO_(3))2和少量Fe(OH)_(3)。结论烧结有利于提高涂层物相的结晶度和涂层表面的致密性,有效发挥涂层物理屏蔽作用。涂层腐蚀防护机制为:腐蚀初期主要发挥片状锌铝粉片层状结构的物理屏蔽作用和腐蚀产物填充涂层破坏区域的自修复作用,随着腐蚀时间的延长,涂层发挥牺牲阳极的阴极保护作用。It is a new type of environmental protection anti-corrosion coating as a substitute for Dacromet coating.It is composed of flake zinc powder,flake aluminum powder,corrosion inhibitor,binder,deionized water,dispersant and other additives,and coated on the substrate.After drying and sintering process,a layer of coating with good corrosion resistance is formed on the substrate.At present,there are few reports on the change of microstructure and corrosion products of chromium-free dacromet coating before and after sintering.Therefore,the change of microstructure of coating before and after sintering and corrosion was studied to explore the anticorrosion mechanism of coating.The Q235 steel was cut into long squares of 25 mm×15 mm×2 mm as the base materials,polished with sand paper of different specifications,and cleaned by ultrasonic.First,silane hydrolysate was prepared,and then metal powder,silane hydrolysate,corrosion inhibitor and other additives were mixed evenly to prepare chromium-free dacromet coating.The coating was coated on the substrate by spraying,and the coating was dried and sintered at 90℃for 15 min and 280℃for 25 min.The corrosion resistance of the coating was tested according to JB/T 6073—1992"Laboratory Full Immersion Corrosion Test of Metal Coating".The corrosion solution was 5%NaCl solution at room temperature.The macromorphology of the specimens before and after corrosion was characterized by AMK-R2S camera.XRD-7000 X-ray diffractometer was used to detect the change of microstructure and composition of the coating under different conditions.TESCAN VEGXMU scanning electron microscope was used to observe the surface and section morphology of the coating before and after sintering and the corrosion morphology of the coating after full immersion test.The chemical elements of the coating were analyzed by energy dispersive spectrometer.The chromium-free dacromet coating is successfully prepared.the surface of the coated steel substrate,which is silver gray,is dense,smooth and have no obvious po

关 键 词：无铬达克罗涂层 制备 组织结构 腐蚀与防护 防腐机制 

分 类 号：TG172[金属学及工艺—金属表面处理]