Durability of vitreous enamel coatings and their resistance to abrasion, chemicals, and corrosion: a review

Vitreous enamels represent a class of coatings with different technological properties, mainly appreciated for the protection they guarantee to the covered substrates. This review introduces enamel coatings, describing their production technologies and presenting the main properties affecting the enamel’s durability. Firstly, this review article introduces the most important studies regarding the improvement in abrasion resistance, highlighting both successes and failures. Afterward, the work reveals an outlook about the resistance to chemicals, underlining the good resistance of enamels toward acidic chemicals and discussing the results of studies aimed to improve their performances toward alkaline solutions. This review also considers the corrosion protection property of enamels, highlighting the high barrier effect they provide against the absorption of aggressive substances toward metal substrates. Finally, new perspectives and possible future research paths are presented, being aware that this kind of coating offers both good product protection and functional integrity over time.

A brief history of porcelain enamel: from artistic enamel to technical enamelling

Porcelain enamel is a glassy material deposited on a metallic substrate and fired at high temperatures (500-900 °C) to form a stable and permanent bond with it through chemical-physical reaction. This coating was developed in ancient times for decorative purposes and it was mainly used to embellish precious objects with colourful and glossy finishing as if to imitate the shining of precious stones. Only from 1760 enamelling of metal objects began to play a technical role. Nowadays vitreous enamel coatings are widely used and appreciated for high-duty technological applications, as they provide good corrosion protection of the covered substrates and they can withstand chemical attack, abrasion, and degradation caused by external agents, maintaining their aesthetical properties unchanged in time. This work is to introduce and describe the history of enamelling from ancient times to the modern era, revealing the glorious past of this material for decorative purposes and its use as a technical coating from the First Industrial Revolution onward.   

Modification of the Mechanical Properties of Vitreous Enameled Aluminium Substrate Adding Graphene Flakes

Vitreous enamel is a very interesting materials thanks to its glassy nature, which permits to obtain high protection against corrosion and fire. In addition, the smooth surface with an elevate hardness favors good abrasion resistance. However, a negative aspect of this kind of coating is the high brittleness, which limits the application in case of impulsive or high loads. The nucleation and propagation of cracks leads to the destruction of layer integrity with loss of properties. In recent years graphene has received increasing attention as toughening addictive for organic and metal coatings as well as composite materials. This work is a first attempt to evaluate if the addition of graphene in an enamel deposit can increase its mechanical properties. The graphene was mixed with the dry frit. A milling process was then carried out before producing the torbida. In this way the formation of graphene clusters and accumulations is prevented. The addition of 1% graphene has shown to be effective in the increase of mechanical properties without negative influence on the deposit microstructure.