Understanding the role of thin film pre-treatments on steel surfaces

金属基材和有机保护涂层之间的界面在决定涂漆金属产品的长期防腐蚀性能方面起着至关重要的作用。在施加有机涂层系统以防止腐蚀之前，金属表面经受清洁方案，通常涉及暴露于碱性环境，然后进行沉积薄无机膜的预处理。这反过来提供了一种惰性表面，其改善了与有机基底漆涂层的粘附性，并且在某些情况下，还在金属-有机涂层界面处提供了额外的主动腐蚀保护。该项目是巴斯夫涂料有限公司与斯旺西大学和伦敦帝国理工学院合作的更大合作伙伴关系的一部分，其主题将涉及进一步了解应用于金属表面时保护性有机涂层的腐蚀引起的失效。该项目的主要重点将是在应用防腐有机涂层系统之前，对金属表面对耐久性的影响有一个基本的了解。该研究将集中在两个感兴趣的具体领域：（i）预处理前清洁金属表面的化学性质，以及这如何影响当前最先进的无机转化涂层的形成和组成。(ii)预处理表面的形貌和化学成分对防腐蚀有机涂层耐久性的影响，最初集中在一个简单的模型油漆系统上。研究将通过扫描开尔文探针（SKP），扫描振动电极技术（SVET），以及斯旺西大学腐蚀研究小组实验室中的动电位和电化学阻抗谱方法。表面化学和结构表征将使用一套仪器进行，包括X射线光电子能谱（XPS）、掠射角X射线衍射（XRD）和场发射枪扫描电子显微镜（FEG-SEM）。项目任务：- 调查各种行业标准化学清洗技术对冷轧镀锌钢和锌镁铝（ZMA）表面化学的影响合金涂层钢基材。研究清洁制度对使用当前预处理技术（如磷酸盐、锆酸盐和钛酸盐）形成无机薄膜效率的影响。研究清洁和预处理的表面在涂覆有机涂层时对耐腐蚀性的影响。对于钢和镀锌钢表面，这将包括通过阴极剥离和阳极驱动的有机涂层失效评估有机涂层失效。

The interface between a metal substrate and a protective organic coating plays a vital role in determining the long-term anti-corrosion performance of painted metal products. Prior to the application of an organic coating system to protect against corrosion, the metal surface is subjected to a cleaning regime, typically involving exposure to an alkaline environment, followed by a pre-treatment which deposits a thin inorganic film. This in turn provides an inert surface which improves adhesion with organic-based primer coatings, and in certain circumstances, also offers additional active corrosion protection at the metal-organic coating interface. This project forms part of a larger partnership involving BASF Coatings Ltd, in collaboration with Swansea University and Imperial College London, where the main theme will involve furthering the understanding of corrosion-induced failure of protective organic coatings when applied to metal surfaces. The principal focus of this project will be directed towards a fundamental understanding of the influence of the metal surface prior to the application of a corrosion protective organic coating system on durability. The research will concentrate on two specific areas of interest:(i) the chemical nature of the cleaned metal surface prior to pre-treatment and how this affects the formation and composition of current state-of-the-art inorganic conversion coatings.(ii) the influence of the topography and chemical composition of the pre-treated surface on the durability of a corrosion protective organic coating, initially concentrating on a simple model paint system.The investigation will be carried out using comprehensive in-situ and ex-situ electrochemical characterization by means of Scanning Kelvin Probe (SKP), Scanning Vibrating Electrode Technique (SVET), alongside potentiodynamic and electrochemical impedance spectroscopy methods in the laboratories of the Swansea University corrosion research group. Surface chemical and structural characterization will be carried using a suite of instrumentation including X-ray-photoelectron spectroscopy (XPS), glancing angle X-ray diffraction (XRD), and field emission gun scanning electron microscopy (FEG-SEM).Project Tasks: - Investigate the influence of various industry standard chemical cleaning technologies on the surface chemistry of cold-rolled galvanised steel and zinc-magnesium-aluminium (ZMA) alloy coated steel substrates.- Study the effect of cleaning regimes on the efficiency of thin inorganic film formation using current pre-treatment technologies such as phosphate, zirconate and titanate-based types.- Investigate the influence of both the cleaned and pre-treated surface on resistance to corrosion-driven failure when overcoated with an organic layer. For steel and galvanised steel surfaces, this will include an evaluation of the organic coating failure via cathodic disbondment and anodic-driven organic coating failure.