# Porcelain Enamel Coatings for Building Facades
## 4 Conclusions  
In this work, different laboratory accelerated tests were conducted to test the potential of enameled steel in the architectural sector compared to that of paints, simulating a series of aggressive conditions to which building panels may be exposed during their service life. Two colors were tested, i.e., red and white, to investigate whether the difference in the composition of the frit might affect the durability of the coatings. The obtained enamel panels have a different thickness, much higher for the red coating than for the white coating. In terms of adhesion to the metal substrate, the white coating performed much better than the red coating. These findings may be explained by the higher values of thickness for the red enamel, which might lead to an inadequate firing.  
Overall, enamel coatings displayed higher durability than paints throughout the accelerated tests. Specifically, the enamel coatings displayed:  
* Excellent corrosion protection to the steel substrate, tied to a microstructure where porosity is closed and there are no through defects. Furthermore, the high thickness prevents the electrolyte contact with the substrate.
* High chemical resistance to aggressive alkaline pH and to aggressive solvents.
* Good color stability. While the white enamel showed excellent color stability during all the conducted accelerated tests, the red enamel displayed a slight color variation after exposure to UV-B radiation and after the soiling and weathering accelerated tests. Nonetheless, the color variation for red enamel is still significantly smaller than the variation for painted samples.  
Ultimately, this work shows the potentiality of enamels as coatings for outdoor use. Indeed, they successfully resisted the aggressive situations tested, aimed at simulating the spectrum of exterior conditions to which coated panels for outdoor use might be exposed.  
Figure 10: Mass loss during the PEI abrasion test.  
In addition to their high durability, enamels are advantageous in terms of aesthetics; in fact, high gloss values were reported for this type of coating, showing how exterior appearance is combined with good resistance. Eventually, despite the higher initial costs, all these aspects would reduce the requirement for maintenance procedures, making enamel panels environmentally sustainable as well.  
Further studies are needed to foster the spread of enamel coating in the architectural sector. The main issue to address would probably be a reduction in the costs of production to make enamel economically competitive compared to the current favorite options and to encourage its industrial use. Then, future outlooks should be aimed at rendering the coating phase \"greener\". In addition to the architectural sector, an expansion of the enamel market can also be foreseen in the field of transportation (consider, for example, tunnels and galleries), where exposure to aggressive external environments demands high coating durability.  
A.Z. methodology, validation, investigation, data curation, writing--original draft; M.C. methodology, validation, data curation, writing--original draft, writing--review and editing; S.R. resources, writing--review and editing, supervision, project administration. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The data presented in this study are available on request from the corresponding author.  
The authors greatly acknowledge CISP (Milan, Italy) and in particular [PERSON] and [PERSON] for the preparation of the samples.  
The authors declare no conflict of interest.