Due to the mainly empirically determined parameters in the enamel industry, thick film quality and the reduction of manufacturing failures are mainly based on the expertise of the enamel community. If parameters are forced to change, for example due to increasing material prices or the ban of certain additives, knowledge-based process development is required.
 
It is well-known from enamel research that precipitates form at the interface between enamel ground coat and steel, which are essential for good adhesion. Those lead to an interlocked metal-glass interface and are triggered by redox-driven processes in a glass layer saturated with ferrous iron. Previous studies have shown that precipitation not only contributes to adhesion through an interlocking interface but also form nano crystallites that are finely distributed in the enamel glass matrix.
 
Electron-transparent STEM (scanning transmission electron micscoscopy) cross sections are particularly useful to investigate the microstructure of the enamel-steel interface in greater detail. In addition to atomic resolution imaging, crystal parameters can be determined using spatially resolved diffraction. STEM can be used to display material contrast and, together with an EDX (energy-dispersive X-ray spectroscopy) system, elemental maps can be generated and compositions can be specified.
 
Current developments in STEM-EELS (Electron Energy Loss Spectroscopy) technology can also provide new impetus in enamel research: parameter-driven changes to the glass-metal interface can be examined even more comprehensively if this spectroscopic approach is chosen. Local investigation of the Fe2+/Fe3+ ratio on the nano scale in the enamel glass matrix can further substantiate the correlation with suppressed phase separation or crystallisation. Furthermore, differentiation between metallic and metal oxide inclusions is possible.
 
The parameter study presented intends to illustrate microstructure-property relationships and aims to highlight the possibilities offered by the aforementioned techniques and their potential added value to the enamel industry.