BE1031221B1 - LOW/LITHIUM-FREE ENAMEL COMPOSITIONS - Google Patents

Abstract

The present invention provides new enamels or compositions that are low or lithium-free, without sacrificing material properties, and useful for coating metal surfaces consisting of cast iron or steel.

Description

LOW/LITHIUM-FREE ENAMEL COMPOSITIONS

TECHNICAL FIELD OF WORK

The invention is in the field of vitreous enamel coatings, more specifically vitreous enamel coatings and compositions for iron and steel types. The invention provides a method for obtaining low- or lithium-free coatings in a one-layer system that meets the standards regarding processing temperature, impact resistance, chemical resistance and scratch resistance, in various application areas.

BACKGROUND OF THE INVENTION

Enamel can be classified as a glass due to its composition which is mainly based on silicon dioxide (>30wt%) and a number of other metal oxides and non-metal oxides cross-linked into a three-dimensional network. Enamelling involves applying an enamel layer to the steel/cast iron object that reacts with the metal surface during firing, creating a chemical and/or mechanical bond between the metal and the enamel layer.

As a result of this bonding, a durable glass coating is formed on top of the substrate that serves as a protective layer. The protected substrate thus exhibits increased impact resistance, chemical resistance and scratch resistance.

To make the enamel layer usable at a usual firing temperature, lithium oxide is often added to the glass so that the sintering and melting temperature decreases. However, lithium is an increasingly scarce raw material due to its frequent use in applications such as mobile phones, laptops, cameras and electric cars. There is therefore a need for enamel compositions that are low in or lithium-free, for use on cast iron and steel, without sacrificing workability, impact resistance, chemical resistance and scratch resistance.

The current invention provides a solution to the above problem and makes it possible to use lithium-poor or lithium-free direct-on enamel in the future.

SUMMARY OF THE INVENTION

The invention provides the following aspects:

Aspect 1. A frit composition useful for coating cast iron and/or steel substrates comprising the following components: a) 40.00-60.00 wt% SiO2, preferably 50.00-55.00 wt% SiO; ; b) 8.00-22.00% by weight Na2O, preferably 12.00-18.00% by weight Na:0; c) 0.10-5.00 wt% K20, preferably 1.50-4.50 wt% K20;

d) 0.10-5.00 wt% CaO, preferably 1.50-4.50 wt% CaO; e) together 1.00-13.00% by weight TiO; and ZrO, preferably together 2.00-10.00 wt% TiO; and

ZrO:; wherein the composition comprises 0.00 to 0.04% by weight of Li:O, preferably 0.00% by weight of Li2O.

As used herein, the term “low-lithium composition” refers to a composition comprising at most 0.04 weight percent LisO, preferably comprising at most 0.02 weight percent Li2O, preferably comprising at most 0.01 weight percent Li2O. The term “lithium-free composition” refers to a composition with 0.00 weight percent Li:O. Preferably, the frit compositions mentioned are lithium-free. Preferably, the enamel compositions mentioned are lithium-free.

Aspect 2. The frit according to aspect 1, which further comprises: together 7.50-20.00 wt.% B20:3 and Al:O3, preferably together 10.00-17.00 wt.% B20:3 and Al;0 : includes.

Aspect 3. An enamel composition comprising one or more frits, with frit composition according to one of aspects 1 or 2; preferably wherein the enamel composition comprises 0.00 to 0.04% by weight of Li,O, preferably 0.00% by weight of Li2O.

Aspect 4. The use of the enamel composition according to aspect 3, for coating cast iron and/or steel surfaces.

Aspect 5. The use according to aspect 4, for coating any object selected from the list including: boilers, pots, casserole rolls, sauce pans, (sauce) pans, frying pans, wok pans and any associated lids thereof; ;baking oven and baking trays, and roasting or grilling racks; barbecues, oven walls, stoves, decorative fireplaces and fireplaces; billboards and bathtubs; architectural panels; silos; heat exchangers.

Aspect 6. The use according to aspect 5, for coating a boiler, wherein the one or more frits comprise the following components: a) 40.00-60.00 wt% SiO:, preferably 45.00-55.00 wt%, more preferably 52.00 wt%; b) 0.10-3.00% by weight Al;O3, preferably 1.00-2.00% by weight, more preferably 1.50% by weight; c) 8.00-14.00 wt% B:03, preferentially 9.00-12.00 wt%, more preferably 11.00 wt%; d) 0.10-5.00 wt% BaO, preferably 0.30-2.00 wt%, more preferably 0.50 wt%; e) 2.00-8.00 wt% CaO, preferably 3.00-5.00 wt%, more preferably 4.00 wt%;

f) 0.10-1.50 wt% CoO, preferably 0.50-1.20 wt%, more preferably 0.80 wt%; g) 2.00-5.00 wt% KO, preferentially 3.00-5.00 wt%, more preferably 4.00 wt%; h) 12.00-22.00 wt% Na:0, preferably 15.00-19.00 wt%, more preferably 17.50 wt%; i) 0.00-5.00 wt% of TiO, preferably 1.00-4.00 wt%, more preferably 1.40 wt%; j) 0.00-5.00 wt% of ZrO:, preferably 1.00-4.00 wt%, more preferably 1.55 wt%; k) 00.00-5.00 wt% of ZnO, F, and Fe:03;

I) 0.00-2.00% by weight MnO:; m) 0.00-1.00 CuO; and n) 0.00-1.00% by weight MgO.

Aspect 7. The use according to aspect 5, for coating a baking oven, wherein the one or more frits comprise the following components: a) 45.00-60.00 wt% SiO:, preferably 50.00-60.00 wt%, more preferably 53.40 wt%; b) 0.10-2.00% by weight Al;O3, preferably 0.50-1.00% by weight, more preferably 0.65% by weight; c) 14.00-18.00 wt% BzOz, preferentially 15.00-16.00 wt%, more preferentially 15.55 wt%; d) 2.00-5.00 wt% CaO, preferably 2.50-4.50 wt%, more preferably 3.00 wt%; e) 0.75-1.50 wt% CoO, preferably 0.90-1.20 wt%, more preferably 1.05 wt%; f) 1.00-5.00 wt% Fe:O3, preferably 2.00-4.00 wt%, more preferably 2.70 wt%; g) 1.00-5.00 wt% KO, preferentially 2.00-4.00 wt%, more preferentially 2.20 wt%; h) 10.00-14.00 wt% Na:0, preferably 11.00-13.00 wt%, more preferably 12.00 wt%; i) 0.00-5.00 wt% TiO, preferably 2.00-4.00 wt%, more preferably 3.80 wt%; j) 0.00-4.00% by weight MnO:;; k) 0.00-3.00% by weight SrO;

I) 0.00-2.50% by weight F; m) 0.00-5.00 wt% of ZrO: and BaO, preferably 0.00-2.00 wt%, more preferably 0.20 wt%; n) 0.00-1.00% by weight MgO; and o) 0.00-0.50 wt.%Cu0.

Aspect 8. The use according to aspect 5, for coating steel pots, casserole rolls, sauce pans, (sauce) pans, frying pans, wok pans and any associated lids; wherein the one or more frits comprise the following components: a) 45.00-60.00 wt% SiO:, preferably 50.00-60.00 wt%, more preferably 51.60 wt%; b) 0.10-2.00% by weight Al;O3, preferably 0.10-1.00% by weight, more preferably 0.45% by weight; c) 10.00-15.00% by weight B:;03, preferably 11.00-13.00% by weight, more preferably 12.40% by weight; d) 2.00-5.00 wt% CaO, preferably 3.00-4.00 wt%, more preferably 3.95 wt%; e) 0.75-1.50 wt% CoO, preferably 0.90-1.20 wt%, more preferably 1.15 wt%; f) 1.00-6.00 wt% Fe:O3, preferably 3.00-6.00 wt%, more preferably 5.50 wt%; g) 1.00-5.00 wt% KO, preferentially 2.00-4.00 wt%, more preferably 2.50 wt%; h) 8.00-15.00% by weight Na2O, preferably 10.00-12.00% by weight, more preferably 11.20% by weight; i) 0.00-6.00 wt% TiO; and BaO, preferably 2.00-5.00 wt%, more preferably 3.80 wt%; j) 0.00-4.00% by weight MnO:;; k) 0.00-2.50% by weight F;

I) 0.00-2.00% by weight of ZrO:; and m) 0.00-0.50 wt%Cu0.

Aspect 9. The use according to aspect 5, for coating cast iron pots, casseroles, sauce pans, (sauce)pans, frying pans, woks and any associated lids; wherein the one or more frits comprises the following components: a) 50.00-60.00 wt% SiO:, preferably 52.00-60.00 wt%, more preferably 52.70 5 wt%; b) 0.10-3.00% by weight Al;O3, preferably 0.50-2.00% by weight, more preferably 1.00% by weight; c) 8.00-12.00 wt% B203, preferably 9.00-11.00 wt%, more preferably 9.80 wt%; d) 0.10-2.00 wt% BaO, preferably 0.10-1.00 wt%, more preferably 0.20 wt%; e) 0.10-5.00 wt% CaO, preferably 2.00-4.00 wt%, more preferably 3.40 wt%; f) 2.00-4.00 wt% F, preferably 2.50-3.50 wt%, more preferably 3.20 wt%; g) 0.10-4.00 wt% K20, preferably 1.50-3.50 wt%, more preferably 1.90 wt%; h) 3.50-6.00 wt% MgO, preferably 3.50-5.00 wt%, more preferably 4.10 wt%; i) 12.00-16.00 wt% Na:0, preferentially 13.00-15.00 wt%, more preferentially 14.90 wt%; j) 8.00-11.00 wt% TiO:, preferably 8.00-10.00 wt%, more preferentially 8.70 wt%; and k) 0.10-2.00 wt% of ZrO, preferably 0.10-1.00 wt%, more preferably 0.10 wt%.

Aspect 10,. A method for forming an enamel coating on a cast iron and/or steel surface, which includes the following steps: a) mixing a frit composition according to one of aspects 1 or 2 with silicone oil and/or water and; minerals, clay, and/or setting salts, to obtain an enamel composition (an enamel powder or an enamel suspension); b) providing a cast iron and/or steel surface, optionally provided with a base coat of enamel composition; c) depositing the enamel composition from step a) on the cast iron, steel surface and/or base coat of enamel from step b); d) firing the enamel composition onto the cast iron, steel surface and/or base coat of enamel, at a temperature of 700 to 900 °C, preferably from 760 to 880 °C, and more preferably from 780 to 860 °C, whereby a enamel coating is formed on the surface.

Aspect 11. The method according to aspect 10, wherein the enamel composition from step a) is fired in step d) for approximately 2 to 15 minutes, preferably 4 to 12 minutes.

Aspect 12. Metal object coated with an enamel composition according to aspect 3.

Aspect 13. Metal object coated according to the method of one of aspects 11 or 12.

DETAILED DESCRIPTION OF THE INVENTION

All terms used herein are to be understood as being known in the art of the invention and have the meaning known therein.

The term “weight percent” refers to percent by weight, abbreviated “% w/w” or “wt. %” and is the weight percentage of the total weight of the enamel composition.

As used herein, the singular forms “a” and “the” include both singular and plural unless the context clearly dictates otherwise.

The terms “includes”, “includes”, “includes” and “includes” as used herein are synonymous and are to be construed as open-ended and do not exclude additional, non-recited members, elements or steps. The term also includes "consisting of" and "consisting primarily of".

The numerical endpoints of the concentration ranges include the actual endpoints as well as a variation thereof of less than 1.0% by weight, preferably less than 0.5% by weight, more preferably less than 0.2% by weight, even more preferably less than 0.1% by weight or less. All numbers and fractions falling within the respective range as well as the stated endpoints form part of the invention.

The term "approximately" as used herein to refer to a measurable value such as a parameter, a quantity, a specific time or the like, is intended to include variations from the prescribed value, particularly variations of +/-10% or less, when preferably +/-5% or less, more preferably +/-1% or less, and more preferably +/-0.1% or less of the prescribed value, to the extent that such variations are appropriate in the respective embodiments of the invention .

It is clear that the value to which the term "approximately" refers is itself also specifically and preferably described.

The term “substantially none” refers to less than 0.1% by weight, preferably less than 0.01% by weight, more preferably 0% by weight.

The term “frit” refers to the frit composition consisting of flakes or granules, which is obtained by melting the mixed components (e.g.) at a temperature of 1200 to 1400 °C, whereby a glass structure is formed, and subsequently cooling this molten glass to room temperature between cooling rollers or in water. In the current context, the terms “frit” and “frit composition” are considered synonymous.

The term “enamel” refers to the enamel composition, which is obtained by grinding frit in combination with additives and colorants into a fine powder or sludge. The enamel is reacted with and adhered to the substrate by firing. In the current context, the terms “email” and “email composition” are considered synonymous.

The term “enamel suspension” refers to a mixture obtained by combining the enamel composition with quartz, clay, setting salts and water. The enamel suspension is burned onto the substrate using a wet enamelling technique. The term “enamel powder” refers to a mixture obtained by combining the enamel composition with potassium feldspar, pigments, and silicone oil. The enamel powder is applied to the substrate by electrostatic powder spraying.

Non-limiting examples of minerals according to the method described herein are quartz and potassium feldspar.

The term “firing” refers to the English term “firing”, the heating step used to allow the enamel composition to finally react with the substrate or surface and can be carried out using any known technology. The enamel composition changes into a glass-hard coating. Firing typically takes place in specially developed ovens, which can have different sizes and use different energy sources for firing the enamel compositions. Examples are so-called lightweight chamber furnaces (box-furnaces), charged furnaces (charge furnaces), tunnel furnaces (tunnel furnaces), conveyor belt furnaces (conveyer-belt furnaces), continuous furnaces (continuous furnaces), with U- or L-type heating chambers . It is important that the ovens have a uniform heat distribution in the oven chamber, with the smallest possible temperature fluctuation depending on time and place in the oven.

The term “coating” refers to the application of one or more enamel layers to an object. In the current context, a cast iron or steel object. The applied enamel layer provides the coated object with properties such as impact resistance, chemical resistance and scratch resistance.

The term “application of the enamel composition” includes all possible techniques for applying the enamel layer (also called “enamel”) to the substrate or surface. More specifically, the term includes: wet dipping, liquid coating (flow coating), spraying, wet electrostatic coating (wet electrostatic coating), electrophoretic coating (electrophoretic coating), powder coating (dusting or dipping), powder electrostatic coating, or combinations of these. In the current context, the substrate is a cast iron or steel surface.

The enamels according to the invention are specially designed for coating surfaces of cast iron and/or steel that must be able to withstand large temperature fluctuations and chemical components such as acids, salts and bases. Non-limiting examples of such cast iron and/or steel surfaces are cooking utensils such as pots, casserole rolls, saucepans, (sauce)pans, frying pans, wok pans, as well as any associated lids thereof, as well as barbecues, roasting or grilling plates, and roasting or grilling racks. Other examples of such surfaces include boilers, architectural panels, silos, heat exchangers, stoves, fireplaces, bathtubs, and billboards.

Depending on the area of application, the coated cast iron and/or steel objects must meet different requirements that have been issued in the form of EN-ISO standards by the European Enamel Association (EEA) (EEA Quality Requirements Manual). In the current context, the following EN-ISO standards are important for the respective quality requirements of the enamel composition:

ISO 28706-1: — resistance to chemical corrosion ((citric) acid at room temperature);

ISO 28706-2: - resistance to chemical corrosion (boiling (citric) acid, water, base and/or steam);

ISO 4531: - issuing of enamelled articles that come into contact with food;

EN 10209: — impact resistance of enamelled articles.

Preferably, the enamels described herein have an adhesion according to EN 10209 of 1 or 2, but at least 3 (where 1 = perfect adhesion, 2 = good adhesion, 3 sufficient adhesion, 4 = insufficient adhesion, 5 = no adhesion). Preferably, the enamels described herein have an acid resistance, defined under the ISO-28706/1 standard, of at least A+ (acid resistance contains 4 classifications, where AA = perfect acid class, A+ = good acid class, A = acid class, no acid class).

The enamels described herein are also suitable for application as a top layer, which can optionally be attached to an enamel base layer, specifically aimed at cast iron and/or steel. An example of such a primer for cast iron is the product GC5028 (PEMCO International}.

An example of such a primer for steel is the product PM1/10/5800/1 (PEMCO

International).

The base coat and top coat are typically applied to the surface via a two-coat-two-fire process. A first base coating is applied via e.g. a spray gun and fired at a temperature between 700 °C-900 °C. A second coating is then applied, also with e.g. a spray gun and fired again but at a lower temperature (700 °C-850 °C).

The enamels described herein are also suitable for application as a single enamel layer, specifically aimed at cast iron and/or steel. Such a single enamel layer is applied to the surface by a one-coat-one-fire process. No primer coating is applied, and 1 enamel layer is applied directly to the substrate and fired at 700 °C-900 °C. This enamel layer then provides both the necessary resistance and the necessary adhesion to the substrate.

The enamels according to the invention use high levels of sodium and/or potassium oxide to obtain an enamel that contains substantially no lithium. The advantage of the current invention is that the resulting composition does not have to compromise on workability, impact resistance, chemical resistance and scratch resistance. The enamels described herein therefore offer a cheaper alternative to existing compositions that can be produced on a large scale.

In addition, the formed glass structure must contain certain percentage values of other metal oxides and non-metal oxides to guarantee compliance with all predetermined requirements.

The aforementioned percentage values depend on the area of application as described below.

Boilers

The corrosion and rust-resistant properties of an enamel coating are the basis for its use in boilers. The steel inside of a hot water boiler is enameled to provide years of guaranteed protection against the heated water. The following table lists the frit compositions described herein for use in boiler applications:

Al;0O3 (0.10 - 3.00 CuO /0.00-1.00 MgO |0.00-1.00 |TiO, |0.00-5.00

B203 |8.00-14.00 |F 0.00-5.00/MnO: | 0.00 - 2.00 |ZrO2 |0.00-5.00

BaO /0.10-5.00 |Fe20: | 0.00 - 5.00 | After:O | 12.00 - 22.00

CaO 2.00 - 8.00 KO 12.00-5.00|ZnO |0.00—5.00

Total | 100.00

CoO |0.10-1.50 LiiO |0.00-0.04 |SiO2» | 40.00-60.00

Baking ovens and plates

Applying an enamel coating to a metal substrate is also used in the furnace industry. Its resistance to varying temperatures in an oven, often between room temperature and 250 °C, makes enamel suitable as a coating. Some ovens use an elevated temperature cleaning cycle (up to 460°C). The emails of this invention are also resistant to this.

To test the suitability of the enamel composition as a coating for ovens and baking trays, high chemical resistance is required, and more specifically food contact resistance. This is measured according to ISO 4531. An enameled plate is exposed to a 3% acetic acid solution at a temperature of 95°C. Performed in 3 different cycles, where one cycle is equivalent to a duration of 2 hours. After each cycle the solvent is renewed, and the concentration of the dissolved components is analyzed. All components may not exceed a prescribed concentration limit. Some examples of the aforementioned limit values according to |SO4531 are listed in the following table:

Utebord OO :Ïj{: À - - > "> > LL ‚Al | Ba Gj 0 5D ON) ODV. ee 2

Loom net N 1000 | 1200 | 5 | 100 | 250 | 480 | 140 | 10 | 10 a.m

One of the important innovative aspects of the current invention is that the composition of the lithium-poor or -free enamel leads to good chemical resistance and good adhesion.

The following table lists the frit compositions described herein for use in ovens and plates:

Al;O3 |0.10- 2.00 CuO |0.00-0.50/ MgO |0.00-1.00 SrO 0.00 - 3.00

B203 14.00 - 18.00 | F 0.00 - 2.50 | MnO: | 0.00 - 4.00 TiO2 |0.00-5.00

BaO |0.00-2.00 FezO3 | 1.00-5.00 | Na:O |10.00-14.00 |Zr0, | 0.00-2.00

CaO |2.00-5.00 KO |1.00-5.00|NiO |0.00-— 1.50

Total | 100.00

CoO |0.75-1.50 LiiO |0.00-0.04 |SiO: | 45.00 - 60.00

Cooking utensils

The lifespan of cooking pots & pans is extended by the use of enamel. Due to the difference in substrate between cast iron and steel, both will be discussed separately.

The following table lists the frit compositions described herein for use in steel cookware:

ALO: |0.10-2.00 |CuO |0.00-0.50| MgO | 0.00 - 1.00 0.00 - 5.00

B203 | 10.00-15.00 |F 0.00 - 2.50 | MnO: | 0.00 - 4.00

BaO |0.00-6.00 |Fez:O; |1.00-6.00 | NazO | 8.00 - 15.00

Total | 100.00

CaO |2.00-5.00 |KO 1|1.00-5.00 NiO |0.00—1.50

CoO |0.75-1.50 |LizO |0.00-0.04 |SiOz |45.00-60.00

The high silicon content, whether or not combined with titanium dioxide, leads to high acid resistance. Addition of bonding oxides, network breakers & others to this rigid network leads to a lithium-poor or -free formula that meets the basic requirements.

Cast iron products are higher in mass due to greater thickness of the substrate, which increases the firing time compared to steel products. The firing period varies between 10 to 20 minutes, at a firing temperature of 740 - 800°C.

The following table lists the frit compositions described herein for use in cast iron cookware:

Al;03 |0.10-3.00 |F 2.00 — 4.00 | After:O | 12.00 - 16.00

B203 |8.00—12.00 |K;O /0.10-4.00/SiO2 | 50.00 - 60.00

Total | 100.00

BaO /0.10-2.00 |MgO /3.550-6.00|Ti0: |8.00- 11.00

CaO |0.10-5.00 |LizO |0.00—0.04 |ZrO; | 0.10—2.00

EXAMPLES

Example 1: Boilers & heat exchangers

The frit composition SP-HWT 9 leads to the enamel suspension Example 1 after mixing with quartz, clay, setting salts and water. The enamel suspension is applied to the substrate via flow coating and fired at 850 °C for 7 minutes. The obtained enamel layer meets all predetermined standards.

Table 1: Overview of the specific components of the frit composition SP-HWT 9 (in weight%) for firing, the resulting enamel suspension Example 1, and the properties of the applied enamel layer.

SP-HWT 9 (wt%) Example 1

Al;03 1.50 Glass mix SP-HWT 9 100.00

B20: 11.00 Quartz 45.00

BaO 0.50 Clay 6.00

CaO 4.00 Adjusting salts 1.20

CoO 0.80 Water 50.00

CuO 0.30

F 4.00 Adhesion EN10209 2

K20 4.00 10% HCI - 1h ISO28706/1 AA

Li:O 0.00 ISO28706/2 Boiling water 6W 7.80 g/m?

MgO 0.25

MnO2 0.10

After 20 17.50

SiO2 52.00

TiO2 1.00

ZnO 1.50

ZrO > 1.55

The lithium-containing frit composition Boiler-SD leads to Comparative Example 1 after applying the composition via the same method as Example 1. As shown in Tables 1 and 2, the inventive enamel compositions are as performant as the lithium-containing alternatives.

Table 2: Overview of the specific components of the lithium-containing frit composition Boiler-

SD (in weight%) for firing, and the properties of the applied enamel layer

Comparative example 1.

Boiler SD (wt%) Adhesion EN10209 2

Al203 2.00 10% HCl - 1h

B203 11.20 IS028706/1 AA

BaO 0.60

CaO 3.90 1S028706/2

CoO 0.80 Boiling water 6W 7.40 g/m?

CuO 0.30

F 3.20

K20 1.10

Li2O 1.10

MgO 0.25

MnO2 0.10

After 8 p.m. 6 p.m

SiO2 53.00

TiO2 1.40

ZnO 1.50

ZrO: 1.55 100.00

A comparative lithium-free frit composition SP-HWT 2 leads to Comparative Example 2 after applying the composition via the same method as Example 1. As shown in Tables 1 and 3, the inventive enamel compositions exhibit better adhesion to the substrate. Comparative example 2 shows that not any lithium-free enamel composition is suitable for coating boilers. Surprisingly, the inventors have found specific ratios of metal and non-metal oxides to obtain lithium-free enamel compositions that are as performant as the lithium-containing alternatives.

Table 3: Overview of the specific components of the lithium-free frit composition SP-HWT 2 (in weight%) for firing, and the properties of the applied enamel layer. Comparative example 2.

SP-HWT 2 (wt%) Adhesion EN10209

Al;03 0.95

B203 8.50

BaO 1.50

CaO 4.90

CoO 0.90

CuO 0.30

F 2.20

K20 6.50

Li2O 0.00

MnO2 0.45

After 8 p.m. 3 p.m

SiO2 47.65

TiO2 1.70

ZnO 2.65

ZrO > 6.80

Al;03 0.95 100.00

Example 2: Baking oven and plates

The frit composition SP-POESTA 17 leads to the enamel powder Example 2 after mixing with potassium feldspar, pigment and silicone oil. The enamel powder is applied to a steel surface via electrostatic powder spraying and fired at 830 °C for 4 minutes. The obtained enamel layer meets all predetermined standards.

Table 4: Overview of the specific components of the frit composition SP-POESTA 17 (in weight%) for firing, the resulting enamel powder Example 2, and the properties of the applied enamel layer.

SP-PUSTA 17 (wt%) Example 2

Al;03 0.65 Glass mix SP-POESTA 17 | 100.00

B:03 15.55 Potassium feldspar 5.00

BaO 0.70 Pigment FA1260* 1.00

CaO 3.00 Silicone Oil 0.20

CoO 1.05

CuO 0.20 Adhesion EN10209 |2

F 1.25 10% Citric acid —

Fez03 2.70 15' ISO-28706/1 A+

K20 2.20

Li2O 0.00

MnO2 2.70

After 20 12.00

SiO2 53.40

SrO 0.60

TiO2 3.80

ZrO> 0.20 *Pigment FA1260 is a commercial product from Pemco International, similar alternatives can also be used.

Table 5: Overview of the leaching limits of components from the enamel layer Example 2 after a 15 food contact resistance test according to ISO 4531. 1604531 (pob) 1000 1200 100 250 4000 1800 140 *Only the measured and limited elements are included in the table.

The lithium-containing frit composition POESTA-SD leads to Comparative example 3 after application of the composition. As shown in Tables 4 and 6, the inventive enamel compositions are as performant as the lithium-containing alternatives.

Table 6: Overview of the specific components of the lithium-containing frit composition POESTA-

SD (in weight%) for firing, and the properties of the applied enamel layer

Comparative example 3.

POESTA-SD (wt%) Adhesion EN10209 | 2

Al,O3 0.55 10% Citric acid —

B.03 14.90 15' ISO-28706/1 A+

BaO 0.70

CaO 3.00

CoO 1.05

CuO 0.55

F 1.75

Fe:03 2.80

K20 0.50

Li2O 0.60

MnO2 2.85

Na20 11.60

SiO2 54.60

SrO 0.60

TiO2 3.80

ZrO: 0.20 100.00

A comparative lithium-free frit composition SP-POESTA 7 leads to Comparative Example 4 after application of the composition via the same method as Example 2. As shown in Tables 4 and 7, the inventive enamel compositions exhibit better adhesion to the substrate.

Table 7: Overview of the specific components of the lithium-free frit composition SP-POESTA 7 (in weight%) for firing, and the properties of the applied enamel layer. Comparative example 4.

SP-POESTA 7 (wt.%) Adhesion EN10209 | 5

Al,O3 1.00 10% Citric acid —

B;0: 9.80 15' ISO-28706/1 A+

BaO 0.20

CaO 3.40

F 3.20

K20 1.90

Li2O 0.00

MgO 4.1

Na20 14.9

SiO2 52.7

TiO2 12.10

ZrO: 3.20 100.00

Example 3: Cookware (steel)

The frit composition SP-CW 14 leads to the enamel suspension Example 3 after mixing with quartz, clay, pigment, setting salts and water. The enamel suspension is applied to a steel surface via dip coating and fired at 840°C for 4 minutes. The obtained enamel layer meets all predetermined standards.

Table 8: Overview of the specific components of the frit composition SP-CW 14 (in weight%) for firing, the resulting enamel suspension Example 3, and the properties of the applied enamel layer.

SP-CW 14 (wt%) Example 3

Al;O: 0.45 Glass mix SP-CW14 100.00

BO; 12.40 Quartz 5.00

BaO 4.25 Clay 5.50

CaO 3.95 Adjusting salts 0.70

CoO 1.15 Pigment FA1211* 3.15

CuO 1.05 Water 52.00

F 0.95

Fez03 5.50 Adhesion EN10209 3

K20 2.50 10% Citric acid —

Li2O 0.00 15' ISO-28706/1 A+

MnO2 1.20

Na20 11.20

SiO2 51.60

TiO2 3.80 *Pigment FA1211 is a commercial product from Pemco International, similar alternatives can also be used.

Table 9: Overview of the leaching limits of components from the enamel layer Example 3 after a food contact resistance test according to ISO 4531. *Only the measured and limited elements are included in the table

The lithium-containing frit composition SD Cookware Steel leads to Comparative example 5 after application of the composition. As shown in Tables 8 and 10, the inventive enamel compositions are as performant as the lithium-containing alternatives.

Table 10: Overview of the specific components of the lithium-containing frit composition SD

Cookware Steel (in weight%) for firing, and the properties of the applied enamel layer Comparative example 5.

SD Cookware Steel (% by weight) Adhesion EN10209 3

ALO: 0.20 10% Citric Acid —

B,0: 13.15 15' ISO-28706/1 A+

BaO 0.00

CaO 5.70

CoO 1.15

CuO 1.05

F 0.95

Fes:O3 5.50

K20 1.10

Li2O 1.00

MnO2 1.20

Na20 10.60

SiO, 53.60

TiO2 4.80 100.00

Table 11: Overview of the leaching limits of components from the comparative lithium-containing enamel layer Comparative example 5 after a food contact resistance test according to ISO 4531. ‚ Ulloengsimeten | | CN , 18504534(ppb) 11000/1200 | 100 | 250 | 4000 | 480 1800 *Only the measured and limited elements are included in the table

A comparative lithium-free frit composition SP-CW 12 leads to Comparative Example 6 after applying the composition via the same method as Example 3. As shown in Tables 8 and 12, the inventive enamel compositions exhibit better adhesion to the substrate.

Table 12: Overview of the specific components of the lithium-free frit composition SP-CW 12 (in weight%) for firing, and the properties of the applied enamel layer. Comparative example 6.

SP-CW 12 (wt%) Adhesion EN10209 | 5

Al03 0.20 10% Citric acid —

B,0: 13.10 15' ISO-28706/1 A+

CaO 7.70

CoO 1.20

CuO 1.10

F 1.00

Fe203 2.50

K20 2.25

Li2O 0.00

MnO2 1.20 10.60

After20 '

SiO2 53.80

TiO2 7.90

ZrO: 0.50 100.00

Example 4: Cookware (cast iron)

Frit composition SP-DCI 34 leads to the enamel formula Example 4 after mixing with quartz, clay, pigment, steatite, setting salts and water. The enamel suspension is applied to a cast iron surface via wet spraying and firing at 750 °C for 12 minutes. The obtained enamel layer meets all previously established standards.

Table 13: Overview of the specific components of the frit composition SP-DCI 34 (in weight%) for firing, the resulting enamel suspension Example 4, and the properties of the applied enamel layer.

SP-DCI 34 (wt%) Example 4

Al;03 1.00 Glass mix SP-DCI34 | 100.00

B;0: 9.80 Quartz 20.00

BaO 0.20 Clay 5.00

CaO 3.40 Adjusting salts 0.50

F 3.20 Steatite 1.00

K,0 1.90 Pigment FA1211* |4.00

LizO 0.00 Water 52.00

MgO 4.10

Na:0 14.90 10% Citric acid —

SiO2 52.70 15' 1SO-28706/1 A+

TiO2 8.70

ZrO: 0.10 *Pigment FA1211 is a commercial product from Pemco International, similar alternatives can also be used.

Table 14: Overview of the leaching limits of components from the enamel layer Example 4 after a food contact resistance test according to ISO 4531. , 1504531(ppb) 1000 1700 | 100 | 250 4000 | 480 1500 *Only the measured and limited elements are included in the table

The lithium-containing frit composition SD Cookware Cast Iron leads to Comparative Example 7 after application of the composition. As shown in Tables 13 and 15, the inventive enamel compositions are as performant as the lithium-containing alternatives.

Table 15: Overview of the specific components of the lithium-containing frit composition SD

Cookware CI (in weight%) for firing, and the properties of the applied enamel layer;

Comparative example 7.

SD Cookware Cast Iron (% by weight) 10% Citric Acid —

Al03 1.00 15' ISO-28706/1 A+

B203 8.80

BaO 0.20

CaO 3.40

F 3.20

K20 0.40

Li2O 0.60

MgO 4.10

Na20 14.70

SiO2 53.70

TiO2 8.70

ZrO: 1.20 100.00

Table 16: Overview of the leaching limits of components from the comparative lithium-containing enamel layer Comparative example 7 after a food contact resistance test according to ISO 4531. 3 1 .-—Tÿ : 1504%531(ppb) 1000| 1200 | 100 | 250 4000 | 480 1500, *Only the measured and limited elements are included in the table

A comparative lithium-free frit composition SP-DCI 16 leads to Comparative Example 8 after applying the composition via the same method as Example 4. As shown in Tables 13 and 17, the inventive enamel composition exhibits better acid resistance and complies with the food contact standard ISO 4531.

Table 17: Overview of the specific components of the lithium-free frit composition SP-DCI 16 (in weight%) for firing, and the properties of the applied enamel layer. Comparative example 8.

SP-DCI 16 (wt%) 10% Citric Acid — None

ALO: 0.80 15' 1SO-28706/1 | acid resistance

B203 8.50

BaO 1.10

CaO 3.50

F 2.50

K20 3.80

MgO 3.90

Na20 11.60

SiO2 48.70

TiO2 12.20

ZrO: 3.40 100.00

Claims (13)

CONCLUSIONS 1. A frit composition useful for coating cast iron and/or steel substrates comprising the following components: f) 40.00-60.00 wt% SiO 7 , preferably 50.00-55.00 wt% SiO 7 ; g) 8.00-22.00% by weight Na2O, preferably 12.00-18.00% by weight Na:0; h) 0.10-5.00 wt.% K;0, preferably 1.50-4.50 wt.% K;0; i) 0.10-5.00 wt% CaO, preferably 1.50-4.50 wt% CaO; jj together 1.00-13.00 wt.% TiO2 and ZrO,, preferably together 2.00-10.00 wt.% TiO: and ZrO:; wherein the composition comprises 0.00 to 0.04% by weight of Li:O, preferably 0.00% by weight of Li2O. The frit according to claim 1, further comprising: together 7.50-20.00 wt% B2 O3 and Al:03, preferably together 10.00-17.00 wt% B20:3 and Al;0: . 3. An enamel composition comprising one or more frits, with a frit composition according to any one of claims 1 or 2; preferably wherein the enamel composition comprises 0.00 to 0.04% by weight of Li:O, preferably 0.00% by weight of Li2O. 4. The use of the enamel composition according to claim 3, for coating cast iron and/or steel surfaces. The use according to claim 4, for coating any object selected from the list including: boilers, pots, casserole rolls, sauce pans, (sauce) pans, frying pans, wok pans and any associated lids thereof; ;baking oven and baking trays, and roasting or grilling racks; barbecues, oven walls, stoves, decorative fireplaces and fireplaces; billboards and bathtubs; architectural panels; silos; heat exchangers. The use according to claim 5, for coating a boiler, wherein the one or more frits comprise the following components: a) 40.00-60.00 wt.% SiO:, preferably 45.00-55.00 wt. .%, more preferably 52.00 wt%; b) 0.10-3.00% by weight Al;O3, preferably 1.00-2.00% by weight, more preferably 1.50% by weight; c) 8.00-14.00 wt% BzO4, preferably 9.00-12.00 wt%, more preferentially 11.00 wt%; d) 0.10-5.00 wt% BaO, preferably 0.30-2.00 wt%, more preferably 0.50 wt%; e) 2.00-8.00 wt% CaO, preferably 3.00-5.00 wt%, more preferably 4.00 wt%; f) 0.10-1.50 wt% CoO, preferably 0.50-1.20 wt%, more preferably 0.80 wt%; g) 2.00-5.00 wt% K:0, preferably 3.00-5.00 wt%, more preferably 4.00 wt%; h) 12.00-22.00 wt% Na:0, preferably 15.00-19.00 wt%, more preferably 17.50 wt%; i) 0.00-5.00 wt% of TiO, preferably 1.00-4.00 wt%, more preferably 1.40 wt%; j) 0.00-5.00% by weight of ZrO, preferably 1.00-4.00% by weight, more preferably 1.55% by weight; k) 0.00-15.00% by weight of ZnO, F, and Fe:03; I) 0.00-2.00% by weight MnO:; m) 0.00-1.00 wt% CuO; and n) 0.00-1.00% by weight MgO. The use according to claim 5, for coating a baking oven, wherein the one or more frits comprise the following components: p) 45.00-60.00 wt.% SiO, preferably 50.00-60.00 wt. .%, more preferably 53.40% by weight; q) 0.10-2.00 wt% Al:O3, preferably 0.50-1.00 wt%, more preferably 0.65 wt%; r) 14.00-18.00 wt% B:O3, preferentially 15.00-16.00 wt%, more preferentially 15.55 wt%; s) 2.00-5.00 wt% CaO, preferably 2.50-4.50 wt%, more preferentially 3.00 wt%; t) 0.75-1.50 wt% CoO, preferably 0.90-1.20 wt%, more preferably 1.05 wt%; u) 1.00-5.00 wt% Fe;03, preferably 2.00-4.00 wt%, more preferably 2.70 wt%; v) 1.00-5.00 wt% K:0, preferably 2.00-4.00 wt%, more preferably 2.20 wt%; w) 10.00-14.00% by weight Na2O, preferably 11.00-13.00% by weight, more preferably 12.00% by weight; x) 0.00-5.00 wt% TiOz, preferably 2.00-4.00 wt%, more preferably 3.80 wt%; y) 0.00-4.00% by weight MnO:;; z) 0.00-3.00% by weight SrO; aa) 0.00-2.50% by weight F; bb) 0.00-5.00 wt% of ZrO and BaO, preferably 0.00-2.00 wt%, more preferably 0.20 wt%; cc) 0.00-1.00% by weight MgO; and dd) 0.00-0.50 wt.%Cu0. 8. The use according to claim 5, for coating steel pots, casserole rolls, sauce pans, (sauce) pans, frying pans, wok pans and any associated lids thereof; wherein the one or more frits comprise the following components: n) 45.00-60.00 wt.% SiO,, preferably 50.00-60.00 wt.%, more preferably 51.60 wt.%; o) 0.10-2.00 wt% Al:O3, preferably 0.10-1.00 wt%, more preferably 0.45 wt%; p) 10.00-15.00 wt% B:O3, preferentially 11.00-13.00 wt%, more preferentially 12.40 wt%; q) 2.00-5.00 wt% CaO, preferably 3.00-4.00 wt%, more preferably 3.95 wt%; r) 0.75-1.50 wt% CoO, preferably 0.90-1.20 wt%, more preferably 1.15 wt%; s) 1.00-6.00 wt% Fe:03, preferably 3.00-6.00 wt%, more preferably 5.50 wt%; t) 1.00-5.00 wt% K:0, preferably 2.00-4.00 wt%, more preferably 2.50 wt%; u) 8.00-15.00% by weight Na2O, preferably 10.00-12.00% by weight, more preferably 11.20% by weight; v) 0.00-6.00 wt% TiO2 and BaO, preferably 2.00-5.00 wt%, more preferentially 3.80 wt%; w) 0.00-4.00% by weight MnO:;; x) 0.00-2.50% by weight F; y) 0.00-2.00% by weight of ZrO 2 ; and z) 0.00-0.50 wt%Cu0. 9. The use according to claim 5, for coating cast iron pots, casserole rolls, sauce pans, (sauce) pans, frying pans, wok pans and any associated lids thereof; wherein the one or more frits comprises the following components: |) 50.00-60.00 wt.% SiO,, preferably 52.00-60.00 wt.%, more preferably 52.70 wt.%; m) 0.10-3.00 wt% Al;O3, preferably 0.50-2.00 wt%, more preferably 1.00 wt%; n) 8.00-12.00% by weight B:03, preferably 9.00-11.00% by weight, more preferably 9.80% by weight; o) 0.10-2.00 wt% BaO, preferably 0.10-1.00 wt%, more preferably 0.20 wt%; p) 0.10-5.00 wt% CaO, preferably 2.00-4.00 wt%, more preferably 3.40 wt%; q) 2.00-4.00 wt% F, preferably 2.50-3.50 wt%, more preferably 3.20 wt%; r) 0.10-4.00 wt% K;0, preferably 1.50-3.50 wt%, more preferably 1.90 wt%; s) 3.50-6.00 wt% MgO, preferably 3.50-5.00 wt%, more preferably 4.10 wt%; t) 12.00-16.00 wt% Na;0, preferentially 13.00-15.00 wt%, more preferentially 14.90 wt%; u) 8.00-11.00 wt% TiO2, preferably 8.00-10.00 wt%, more preferentially 8.70 wt%; and v) 0.10-2.00 wt% of ZrO, preferably 0.10-1.00 wt%, more preferably 0.10 wt%. 10. A method for forming an enamel coating on a cast iron and/or steel surface, comprising, among others, the following steps: e) mixing a frit composition according to any one of claims 1 or 2 with silicone oil and/or water and; minerals, clay, and/or setting salts, to obtain an enamel composition (an enamel powder or an enamel suspension); f) providing a cast iron and/or steel surface, optionally provided with a base coat of enamel composition; g) depositing the enamel composition from step a) on the cast iron, steel surface and/or base coat of enamel from step b); h) firing the enamel composition onto the cast iron, steel surface and/or base coat of enamel, at a temperature of 700 to 900 °C, preferably from 760 to 880 °C, and more preferably from 780 to 860 °C, whereby a enamel coating is formed on the surface. The method according to claim 10, wherein the enamel composition from step a) is fired in step d) for about 2 to 15 minutes, preferably 4 to 12 minutes. 12. Metal object coated with an enamel composition according to claim 3. 13. Metal object coated according to the method of one of claims 10 or 11.