Architecture: Introduction


Immune to corrosion
Vitreous enamel in the architecture

A natural material born from fire, immune to corrosion, as pure as glass, available in a huge range of colours that remain stable over time and in any atmospheric conditions, recyclable…
A coating that offers a highly versatile, global response to many different sectors of industry.

...a natural material
Although it is not exactly technical, this definition tells us many important things. The starting material for vitreous enamel, called the “frit”, is a mixture of different substances found in nature: silicates, borates, carbonates, oxides etc.

...born from fire
The frit is the product of smelting these materials and subsequently cooling them back down. According to how it is cooled (in water or between two metal rollers), it takes the form of either crumbling granules or small flakes.

...immune to corrosion
The composition of the frit, i.e. the vitreous component of the enamel, varies considerably, according to:
:: the support to which it is applied (steel, aluminium, cast iron, glass);
:: the functionality to deliver to the enamel, for fitting the usage requirement.
As a general rule, all vitreous enamels can be said to be resistant to:
:: All organic solvents,
:: All normal detergents (pH>7),
:: All neutral saline solutions (pH=7),
:: All acids (at room temperature) except hydrofluoric acid.

…as pure as glass
Enamel is a borosilicate glass with an amorphous structure that gives it a hard, compact surface, with no porous areas and impermeable to liquids. It neither absorbs nor transmits odours or flavours.
It inhibits the proliferation of bacteria.
It is easy to clean.

A vitreous structure The structure of a Na2O – SiO2O glass


A natural material,
environmental friendly,
recyclable
...Available in a huge range of colours
Enamels are generally coloured using inorganic pigments or metal oxides added to the frit during the grinding phase.

...Easy to decorate
In addition to lending themselves to all sorts of colours, enamelled surfaces can also be decorated using various industrial systems (decalcomania, serigraphy) and artistic methods

...Recyclable
Both the elements that are used to make the frit and the supports (steel, cast iron, aluminium and glass) on which the enamels are applied are recyclable without any problems, as they contain no polluting substances.
Once an enamelled product’s life cycle is over, it can be used again to produce steel or aluminium.

Vitreous Enamel Typical Composition
Component
Mineral
Functions
SiO2
Quartz - Feldspar
Refractory component, hardens the vitreous      system, adds chemical resistance and increases viscosity.
B2O3
Borates
Flux that produces the vitreous matrix, reduces viscosity and increases surface hardness.
Na2O
K2O
LiO2
Albite
Feldspar - Microcline
Spodumene - Petalite
Alkaline components that lower the temperature at which glass softens, reduce its elasticity and increase its brilliance.
Al2O3
Feldspar - Corundum
Increases viscosity and chemical, mechanical and thermal resistance, reduces the expansion coefficient and favours an opaque finish. 
 ZrO2
Zirconium
Improves resistance to acids, to knocks and to shocks, acts as an opacifier.
ZnO
Zincite, Blende, Wurzite
Excellent flux, lowers the expansion coefficient and improves brilliance and surface quality.
CoO
Cobaltite
A very strong adherence agent, it produces a structure with lots of small, well distributed bubbles.
NiO2
Niccolite
A second adherence agent, it produces a structure with a small number of large bubbles.
CuO Copper When combined with primary bonds, it triggers the adherence reaction at lower temperatures.
MnO2 Manganese dioxide Produces brown-coloured frits, intensifies dark colours and acts as an oxidant and as a weak bond.
Sb2O3
Antimonite
Produces a high degree of opacity and improves resistance to acids.
TiO2
Rutile, Anatase, Brookite
The epitome of opacifiers, it increases whiteness, brilliance and resistance to acids and heat.
BaO
CaO
MgO
Barite
Dolomite-Limestone
Periclase
Alkaline-earthy components that integrate anti-acid enamels, increasing their resistance, their smelting facility and their viscosity.
P2O5
Apatite
Alters the opacity of the finish, improves colour stability and reduces chemical resistance.
F2 Fluorite Softens glass and influences the opacity.

Table a – Typical composition of a ground coat enamel
Felspar
21.0
Borax
35.0
Quartz
28.0
Sodium hydrogen carbonate
4.5
Sodium nitrate
4.0
Potassium and Sodium Fluosilicate
5.0
Cobalt oxide
0.5
Nickel oxide
0.5
Manganese dioxide
1.5

Table b - Typical composition of a white Ti cover coat
Felspar
4.5
Quartz
25.6
Sodium hydrogen carbonate
24.2
Sodium nitrate
2.4
Calcium carbonate
3.4
Cryolite
2.6
Sodium antimonate
0.8
Titanium dioxide
17.2
Zinc oxide
19.5

 

 

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