碳钢表面硅烷化关键技术与相关基础研究

Painting system is the majority of use for corrosion protection of metals. Most of the conventional painting systems using chromate or phosphate as the pretreatment layer and ensuring the promising corrosion protection properties, however, are environmentally unfriendly. For these reasons, strict environmental regulations will ban the use of chromate and phosphate compounds in corrosion protection industry in the near future. Silanization, based on the use of organosilanes, has been recognized as the most promising replacer for phosphating and chromating processes during the recent years’ exploration and practice. This technique is willing to be practically used in industrial scale in the near future. Though silanization has achieved practical application on aluminum (alloys) and galvanized steel substrates, till now this technique has failed for industrial use on carbon steel due to the technical difficulties. As the response to the above-mentioned problems, the possible reasons are raised in this proposal. We believe that the high porosity of naturally formed ferrous oxides, the critical condition for the formation of hydroxides of iron, the un-uniform phase distribution on the surface of carbon steel, and the lack of scientific point of knowledge of silanization on carbon steel, are all the interpretations. Accordingly, the project plans to deeply investigate some basic problems of silanization at carbon steel substrates, emphasizing the influencing rule of surface silanzation of carbon steel by its surface statues. After then, solutions are proposed to resolve the existing problems. We suggest optimizing the surface cleaning parameters, introducing a surface modification process, and re-considering the optimal types of silane compound suited and ways of formulating. Both the process and mechanistic investigations will be covered. The above-mentioned investigation will provide silanization of carbon steel the theoretical and practical guidance, and ultimately promote the replacing progress of traditional surface pretreatment industry by such a new generation of technique.

涂层与涂装是金属材料最常用的防护手段。然而，传统以磷化层或铬酸盐为预处理层的涂装体系，虽然性能可靠，但对环境不友好，已开始被限制或停止使用。经过多年的探索与实践，硅烷化被公认是目前最有望取代传统技术的新型绿色预处理工艺，已在铝合金和镀锌钢板上取得实际应用，但由于成膜困难，硅烷化技术在工业用量最大的结构金属材料—碳钢表面至今仍未取得工业应用。面对这一现实，项目分析了导致上述现象的可能的原因（铁基材料自然氧化物膜疏松多孔、羟基氧化物形成条件苛刻、碳钢表面组织分布不均匀、相关基本规律尚缺乏），提出开展相关基础研究，关注碳钢表面状态对硅烷化的影响规律，同时开展相应的对策研究（优化清洗工艺、引入表面改性工艺、重新审视适合碳钢的硅烷种类与复配方式等）。通过上述研究，为碳钢表面的硅烷化提供理论与应用基础，进而最终意在推动整个金属表面涂装前处理行业在技术上的更新换代。

硅烷化被公认是目前最有望取代传统技术的新型绿色预处理工艺，应用于金属表面涂装防护体系。但是，虽然这一技术在铝合金和镀锌钢板上已取得实际应用，却在碳钢，这一工业用量最大的结构金属材料表面仍未能实现工业应用。面对这一现实，本项目从“碳钢表面硅烷化溶液组分优化”、“碳钢表面预氧化和表面调整工艺研究”、“分子层面理解硅烷化影响规律”三方面，试图理解上述存在的问题，并提出相关解决策略。项目取得如下研究结果。. （1）提出了适用于碳钢表面硅烷化的硅烷组分，即通过含官能团硅烷（如MAP）、不含官能团的双硅烷（如BTSE）和无机硅烷组分（如TEOS）相复配，显著增强硅烷膜的短期防护性能和涂装性能，这源于MAP与后续涂层的化学键合、BTSE优异的物理阻挡性能和TEOS增强硅烷成膜动力等。. （2）发现了表面预氧化（如化学氧化或电化学氧化）和表面调整工艺均显著增强碳钢表面的硅烷化能力。进一步的研究发现，导致这一现象的根本原因是上述预处理技术导致碳钢表面羟基化增强。. （3）分子动力学模拟结果显示，碳钢表面不同物相的硅烷化能力有显著差异，铁的羟基化表面最利于硅烷成膜，而杂质相如Fe3C表面最不利于硅烷化；与其他硅烷组分相比，BTSE与碳钢基体不同物相组分表面均表现出较高的结合能，这可能得益于其双硅烷的特性。.