新型达克罗涂层的制备与组织结构

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8~12 μm。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Zn5(OH)8Cl.H2O、Al5Cl3(OH)12.4H2O、Zn5(OH)6(CO3)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。

Preparation and Microstructure of New-type Dacromet Coating

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.