Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23D—ENAMELLING OF, OR APPLYING A VITREOUS LAYER TO, METALS
  • C23D5/00—Coating with enamels or vitreous layers
  • C23D5/06—Coating with enamels or vitreous layers producing designs or letters
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
  • B05D3/20—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by magnetic fields
  • B05D3/207—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by magnetic fields post-treatment by magnetic fields

Definitions

• the present invention generally relates to an article provided with an enamelled coating incorporating anisotropic particles (flake or fiber type) and can be used on any type of substrate, especially metal.
• the present invention also relates to a method of applying such a coating on a support.
• the target area is in the first place that of heating articles.
• a heating article is understood to mean an article which has its own heating system, or an article which is heated by an external system and which is capable of transmitting the heat energy brought by this system to a heating system. material or object third party in contact with said article, or an article which is intended to receive another previously heated article.
• culinary articles such as frying pans, saucepans, woks, pancakes, casseroles, pots, casseroles, etc.
• lids heating and mixing bowls heating food preparation apparatus or beverage.
• the present invention may also relate to any other type of surface and articles, such as tableware such as trivets, soles of an iron, curling irons, and straightening irons, radiators, towel racks or wood stoves, or barbecue plates, barbecue chests or barbecue vats, flat heating hoods.
• Enamelled coatings are particularly popular in the field of heating articles, particularly culinary, and in that of irons, and more specifically iron soles.
• an enamel coating is therefore an ideal compromise to coat the metal cap of an iron soleplate because it has a good thermal resistance, a low coefficient of friction that changes little with temperature, a hydrophilic behavior and resistance to wear. hydrolysis.
• the disadvantage of enamelled coatings for ironing applications lies in their low impact resistance. Indeed, it may appear at the edge coated with the enameled cap (and more particularly on the periphery of the coated cap), small pieces of enamel, especially if the coating is subjected to shocks caused by handling. Small pieces of enamel may also appear by repeated contact on metal parts attached to the ironing textiles (buttonholes, snaps, zippers ).
• Enamel coatings are also particularly popular in the field of cookware because they provide colored coatings which not only have good dishwasher resistance, high flame and scratch resistance, but also decorative primordial, often decisive in the choice of the consumer. However, they have the disadvantage of flaking easily in some particularly sensitive areas, which are areas of high stress of the culinary article. These areas are generally located in the curvature areas of the article or in the connection areas with the handle or handles.
• the enamelled coatings also have the disadvantage of having a different thermal expansion depending on the position of the flame at the bottom of the article. However, it is important that the coating has a uniform thermal expansion, otherwise it generates microcracks that interfere with the behavior in the dishwasher.
• the Applicant has developed an enamel coating having flakes, and more generally particles of anisotropic shape, which are oriented substantially perpendicular to the coating formed in the sensitive areas.
• particles essentially perpendicular to the coating is meant, in the sense of the present invention, particles which are predominantly inclined at an angle of between 20 ° and 90 °, preferably between 45 and 90 °, and preferably between 60 and 90 ° with respect to the average plane of the coating.
• the present invention relates to a heating article comprising a support having two opposite faces, at least one of which is covered with a protective coating, characterized in that said protective coating comprises at least one layer of E-mail wherein particles of anisotropic form are dispersed, the enamel layer comprising at least one zone in which the anisotropic particles are substantially perpendicular to the film enamel layer.
• the particles of anisotropic form can advantageously represent 0.05 to 10%, preferably 0.1 to 7%, and more preferably 1 to 5% by weight of the total weight of the enamel layer. Ideally, the particles of anisotropic form represent 2 to 3% by weight of the total weight of the enamel layer (31).
• the resistance to chipping and shocks is significantly improved.
• this zone does not have a thermal expansion different from that of the rest of the coating.
• particles of anisotropic shape the meaning of the present invention is understood to mean particles whose characteristic dimensions are not identical in all directions, such as, for example, fibers (of essentially one-dimensional shape) or flakes (of essentially two-dimensional or flat shape). )
• particles essentially perpendicular to the film is meant in the sense of the present invention, particles that are predominantly inclined at an angle between 20 ° and 90 ° relative to the mean plane of the film.
• Such an orientation of the anisotropic particles can be obtained in different ways, depending on the type of anisotropic particles used.
• the orientation substantially perpendicular to the coating layer may, for example, result from positioning related to the coating application process, such as, for example the orientation through a monodirectional applicator as a micro ⁇ nozzle.
• the essentially perpendicular orientation of the anisotropic particles with respect to the coating layer may be resulting from a positioning consecutive or simultaneous to the application of the coating, such as for example the orientation of magnetizable particles under the effect of a magnetic field or particles electrisables under the effect of an electric field.
• magnetizable particles means particles capable of being oriented under the effect of a magnetic field.
• Magnetizable particles can be of different natures.
• the magnetizable particles may advantageously be particles comprising at least one ferromagnetic metal.
• They may be homogeneous in nature, that is to say made of the same material or of composite nature, that is to say that the magnetizable particles have a core-shell structure, in which the ferromagnetic metal is in the core and or in the envelope of said particles.
• composite magnetizable particles particular mention may be made of mica flakes coated with a ferromagnetic material, such as, for example, mica flakes coated with a ferrite of the form (MO, Fe 2 O 3) where M is a metal divalent, for example mica flakes coated with Fe 3 O 4 (magnetite) or Fe 2 O 3, or FeO.
• M is a metal divalent
• Fe 3 O 4 magnetite
• FeO FeO
• Other materials having ferromagnetic properties may also be used: mention may be made, for example, of cobalt, nickel, or Heussler alloy consisting solely of non-ferromagnetic metals (61% Cu, 24% Mn, 15% Al) , or some rare earths such as lanthanides, copper-manganese oxides and aluminum.
• coated mica flakes lies in the fact that they are particularly resistant to the high firing temperature of metal enamels, ie temperatures ranging from 550 ° C for enamels on aluminum to 850 ° C for enamels on steel or cast iron.
• Mention may also be made of stainless steel fibers coated with a sol-gel material, as protection against corrosion during the stages of implementation of the coating, or flakes whose core is made of ferromagnetic metal and the envelope is made of a sol-gel material.
• the coating according to the invention may further advantageously comprise non-magnetizable particles to improve the reinforcement of the coating.
• non-magnetizable particles are understood to mean non-magnetizable or weakly magnetizable particles having a zero or low magnetic moment (less than 1 emu / g).
• These non-magnetizable particles may be of any shape (spherical, fiber or flake or
• non-magnetizable particles that can be used in the context of the present invention, mention may be made especially of mica flakes, and mica or silica flakes coated with titanium dioxide.
• the protective coating of the present invention may furthermore advantageously comprise, adjacent to the zone in which the particles are substantially perpendicular to the enamel coating layer, at least one zone in which the particles are arranged substantially parallel and / or random to the enamel layer in the form of a film, so as to strengthen the sensitive areas.
• particles essentially parallel to the enamelled coating layer is meant in the sense of the present invention, particles that are predominantly inclined at an angle between 0 ° and 20 ° with respect to the coating layer.
• the enamel layer of the protective coating according to the invention may comprise a single continuous layer and intended to be arranged on a support.
• the enamel layer of the protective coating according to the invention can comprise:
• a transparent undercoat free of magnetizable particles which is continuous and is intended to be placed on a support
• finishing layer in which the magnetizable particles are dispersed, the finishing layer being continuous and partially or completely covering the underlayer.
• a finishing layer is intended to mean a layer which is intended to be in contact with the environment.
• the enamel layer of the protective coating according to the invention can comprise:
• a colored and magnetisable particle-free undercoat which is continuous and is intended to be arranged on a support
• a topcoat in which the magnetizable particles are dispersed the finishing layer being continuous and partially or completely covering the underlayer.
• the enamel layer of the protective coating according to the invention can comprise:
• a transparent or colored undercoat and free of magnetizable particles the underlayer being continuous and intended to be arranged on a support
• a second topcoat in which magnetizable particles are also dispersed, the second topcoat being continuous and partially or completely covering the first topcoat
• the enamel layer of the protective coating according to the invention can comprise:
• a colored underlayer in which magnetizable particles are dispersed the colored underlayer being continuous and intended to be placed on a support
• a transparent topcoat in which are also dispersed magnetizable particles, the topcoat is continuous and partially or completely covering the colored undercoat.
• Such an embodiment has the advantage of mechanically reinforcing each layer and the mechanical connection between each layer.
• the sub-layer may have a thickness of between 5 and 30 ⁇
• the finishing layer or layers may have a thickness of between between 20 and 60 ⁇ .
• the protective coating according to the invention can comprise:
• an enamel layer comprising:
• ⁇ a sub-layer free of magnetisable particles and is transparent or colored, this sub-layer being continuous and adapted to be disposed on a support, and
• middle layer (313) which is either a colored layer, a magnetizable layer which in which are dispersed magnetizable particles (41), said middle layer (313) being continuous and covering partially or completely said underlayer (310), and
• a second coat of clear, non-magnetizable, clear and continuous varnish completely covers the first layer of magnetizable varnish, so as to ensure chemical resistance and hold in the dishwasher.
• the sub-layer may have a thickness of between 5 and 30 ⁇
• the middle enamel layer may have a thickness of between 20 and 60 ⁇ .
• the magnetizable lacquer layer may advantageously have a thickness of between 15 and 40 ⁇
• the protective lacquer layer may have a thickness of between 10 and 20 ⁇ .
• a colored layer (whether it is an underlayer, a topcoat or a layer of varnish) is understood to mean the present invention.
• the enamel layer of the protective coating of the heating article according to the invention may furthermore comprise a discontinuous outer enamel layer, which is screen printed or padprinted.
• the outer layer of enamel can also comprise rounded charges, which are advantageously spherical with a diameter of between 5 and 40 ⁇ , and preferably between 15 and 20 ⁇ , the thickness of the outer layer (32) varying between 10 and 30 ⁇ . These beads protrude from the surface of the outer layer of enamel.
• rounded fillers (or balls) used in the outer enamel layer according to the invention include stainless steel balls, copper, bronze or refractory steel.
• stainless steel balls are used.
• the rounded fillers are advantageously present in the outer layer of enamel in a proportion of 1 to 5% by weight relative to the total weight of the outer layer. These rounded loads make it possible both to increase the wear resistance of the enamel coating and to reduce (when the loads are flush with the surface of the enamel layer) the coefficient of friction due to the decrease. the contact surface between the article and the hob and the lesser hardness of the beads compared to that of the enamel layer. Thus, the coating is easily cleaned and does not present a risk of scratching sensitive surfaces such as glass-ceramic or induction plates.
• the support of the article can be made of a material selected from metals, glass and ceramics.
• supports having a structure:
• a multilayer metal support in part or in whole, comprising from outside to inside the following layers ferritic stainless steel / aluminum / austenitic stainless steel or stainless steel / aluminum / copper / aluminum / austenitic stainless steel, or another aluminum casting cap, aluminum or aluminum alloys lined with a stainless steel outer bottom.
• the subject of the present invention is also a method of manufacturing, on a heating article support, a coating comprising at least one enamel layer in which particles of anisotropic form are dispersed, characterized in that comprises a step of orienting said anisotropic particles by a physical means (for example by applying an electric or magnetic field) or mechanically (for example during the application of the coating using a monodirectional applicator such as a micro ⁇ nozzle) in at least one zone of the enamel layer.
• a physical means for example by applying an electric or magnetic field
• mechanically for example during the application of the coating using a monodirectional applicator such as a micro ⁇ nozzle
• the support and the anisotropic particles are as defined above.
• the method according to the invention may comprise the following steps:
• a drying step preferably at a temperature between room temperature and 150 ° C, followed (e) cooking at a temperature of not less than
• the magnetizable particles are as defined above.
• step d) of orientation of the magnetizable particles is therefore a magnetization step carried out by application of a magnetic field, which is performed either during the application of the enamel composition, or after this application step d), but in any case prior to step e) cooking.
• a protective coating is obtained which simultaneously has a high resistance to chipping and shocks and a homogeneous thermal expansion throughout the coating.
• the step b) of applying the enamel layer may advantageously comprise the following substeps:
• the step b) of applying the enamel layer may further comprise after step b2) but before cooking e), a step b3) of spraying on the non-enamel finish layer.
• a step b3) of spraying on the non-enamel finish layer may further comprise after step b2) but before cooking e), a step b3) of spraying on the non-enamel finish layer.
• the method according to the invention may further comprise, after carrying out a drying step d) of the or layers of finish enamel formed (the drying step is then no longer optional but necessary for this embodiment), a step of application by screen printing on said top enamel layer of a layer of enamel paste, which may or may not include rounded charges.
• Figure 1 shows a schematic sectional view of an article support portion according to the invention according to a first embodiment
• FIG. 2 represents a schematic sectional view of an article support portion according to the invention according to a second variant embodiment (showing two subvariants 2a and 2b);
• FIG. 3 represents a schematic sectional view of an article support portion according to the invention according to a third variant embodiment (showing two subvariants 3a and 3b);
• FIG. 4 represents a schematic sectional view of an article support portion according to the invention according to a fourth variant embodiment
• FIG. 5 shows a schematic sectional view of an article support portion according to the invention according to a fifth embodiment (showing four sub-variants 5a to 5d);
• Figure 6 shows a schematic sectional view of a culinary article support portion according to the invention according to a sixth embodiment
• Figure 7 shows a schematic sectional view of a sole portion of iron according to the invention according to a seventh embodiment
• FIG. 8 shows a bottom view of the iron soleplate shown in Figure 7;
• Figure 9 shows a schematic sectional view of the arrangement of the magnets under a coated article carrier to perform the magnetization step
• Figure 10 is a detailed view of Figure 9 at the zone Z (defined by the edges of two magnets and the air gap);
• FIG. 11 is a top view (photograph) of a sole portion of an iron under which permanent magnets have been arranged in the form of triangular contour strips;
• Figure 12 is a detailed view of Figure 1 at a specific area Z (defined by the edges of two magnets and the gap);
• FIG. 13 represents a series of three images 13A to 13B of scanning electron microscopy (SEM) of an iron sole plate section 3 made at the level of the specific zone.
• SEM scanning electron microscopy
• FIG. 1 there is shown an article support portion according to the invention according to a first embodiment.
• One of the faces 21 of the support 2 is provided with a continuous monolayer film 31 of an enamel coating in which particles of anisotropic shape 41 are dispersed.
• FIG. 1 shows that the film 31 comprises at least one zone 5 in which the particles of anisotropic shape 41 are substantially perpendicular to the film 31.
• This specific orientation of the anisotropic particles 41 in the zone 5 can for example be obtained by magnetization if the anisotropic particles 41 comprise magnetizable particles.
• a permanent magnet in particular of the elastomer type (which limits the magnetization conditions to a temperature below 80 ° C) or an electromagnet.
• a permanent magnet type Ferrite or Neodymium or an electrically-induced magnet.
• the maximum temperature value of the conditions in which the magnetization takes place may then be greater than 80 ° C., but must remain below the curie temperature of the magnets used.
• To obtain a specific holographic image use will be made of a magnet having the desired shape, which will be cut and / or machined in a permanent or electro-induced ferromagnetic material.
• a magnet emitting a magnetic field whose intensity is between 40 and 100 mT, and preferably of the order of 70 m, is used.
• FIG. 1 clearly shows that the magnetizable particles 41 of the monolayer enamel film 31 are oriented perpendicularly to this film in the specific zone 5, according to the field lines produced by the permanent magnet situated just below this zone 5.
• FIG. 2 represents a schematic cross-sectional view of an article support portion 2 according to the invention according to a second variant embodiment, showing two sub-variants illustrated respectively in FIGS. 2a and 2b.
• the two-sub-variants illustrated in FIGS. 2a and 2b differ from the variant embodiment illustrated in FIG. 1 in that the enamel coating in the form of film 31 is bilayered.
• the bilayer coating 31 comprises an underlayer 310 disposed on one of the faces 21 of the support 2 (free of particles of anisotropic shape) and a finishing layer 311 in the form of a continuous film of enamel covering the underlayer 310, the anisotropic particles 41 being included in the topcoat 311.
• the underlayer 210 may be colored, as shown in Figure 2a, or transparent, as shown in Figure 2b.
• the orientation of the anisotropic particles 41 may, in the same way as for the first embodiment variant, be made by magnetization if these anisotropic particles 41 comprise magnetic particles.
• FIG. 3 represents a schematic sectional view of an article support portion according to the invention according to a third embodiment variant, also showing two sub-variants illustrated respectively in FIGS. 3a) and 3b).
• Each of these sub-variants 3a) and 3b) differs from the embodiments illustrated in FIGS. 2a and 2b respectively in that the enamel coating 31 bilayer a second topcoat 312 in which anisotropic particles 41 are also dispersed.
• FIG. 3 also shows that the two-layer enamel coating of FIG. 3 comprises a three-dimensional pattern formed by alternating zones 6 with anisotropic particles 41 essentially parallel to the coating 31 and zones 5 with essentially perpendicular anisotropic particles 41. to the film.
• the specific orientation of the anisotropic particles 41 in the zones 5 will be achieved by magnetization if the anisotropic particles are magnetizable.
• this magnetization can for example be achieved by placing under the support (of substantially circular shape), on the side of the face 22 uncoated, a plurality of concentric permanent magnets elastomer, which emit a magnetic field of the same intensity or different intensities, for example of the order of 80 mT measured independently.
• These concentric magnets may advantageously be in the form of a central disk of small diameter (for example equal to or less than 15 mm) and a plurality of concentric rings arranged around this central disk of a width of the order from 10 to 15 mm.
• magnets can advantageously be arranged on a substrate (for example a stainless steel tray) which can be move perpendicular to the support of the article. This movement can be done by means of a jack which causes the substrate (or plate) close to the article to be magnetized, so as to define a gap.
• a substrate for example a stainless steel tray
• an iron soleplate having a substantially triangular shaped cap to be coated there are for example strips of magnets (for example elastomer under the zones to be reinforced support 22, on the side of the These strips may be continuous or discontinuous and have the substantially triangular shape of the cap They emit a magnetic field of the same intensity or of different intensities, for example of the order of 80 mT measured independently.
• magnets for example elastomer under the zones to be reinforced support 22
• the magnetizable anisotropic particles will then orient themselves along the field lines, that is to say perpendicularly to the support 2 (or to the film 31) at the zones 5 under which a magnet has been arranged (the field lines being perpendicular to the enamel coating 31, and parallel to the support 2 (and therefore to the coating 31) in the zones 6 where the field lines are parallel to the support 2, with a continuum of progressive orientation of the magnetizable anisotropic particles between these two zones.
• FIG. 4 represents a schematic sectional view of an article support portion according to the invention according to a fourth variant embodiment, which is different from the sub-variant embodiment illustrated in FIG. 2a, in that the sub-layer 310 comprises anisotropic particles 41.
• the two-layer enamel coating 31 of FIG. 3 comprises a three-dimensional pattern formed by the alternation of zones 6 with anisotropic particles 41 substantially parallel to the coating 31, and zones 5 with anisotropic particles 41 substantially perpendicular to the film. If the anisotropic particles 41 comprise or are magnetic particles, the orientation of the particles in the zones 5 can be obtained by placing magnets under the support 2.
• FIG. 5 represents a schematic sectional view an article support portion according to the invention according to a fifth embodiment, showing four sub-variants illustrated respectively in Figures 5a) to 5d). These figures show a support 2, one of the faces 21 is coated with an enamel layer comprising:
• ⁇ a sublayer 310 free of magnetizable particles 41, and which is transparent (as shown in Figures 5a and 5b) or colored (as shown in Figures 5c and 5d),
• a middle layer 313 that is a color layer (as illustrated in Figures 5b and 5d), a magnetizable layer which in which are dispersed particles preferably anisotropic magnetizable 41, the middle layer 313 being continuous and covering the sub layer 310).
• the middle layer 313 is itself covered by:
• the specific orientation of the anisotropic particles 41 in the zones 5 will be achieved by magnetization if the anisotropic particles are magnetizable.
• FIG. 6 represents a schematic sectional view of a culinary article support portion according to the invention according to a sixth variant embodiment.
• the support 2 comprises an inner face 22 which is the face oriented on the side of the food that can be received in the frying pan 1, and an outer face 21 which is intended to to be disposed towards an external heat source.
• the support 2 comprises, on its inner face 22, a non-stick coating 7 (for example of sol-gel material or fluorocarbon resin), and on its outer face 21 a coating 3 comprising:
• an enamel layer 31 continues, which is pigmented and contains magnetizable particles 41,
• an outer enamel layer 33 discontinuous which is obtained by screen printing or pad printing, comprising metallic balls 34 (of copper, bronze or heat resisting steel).
• FIG. 7 represents a schematic cross-sectional view of a sole portion of an iron according to the invention according to a seventh embodiment variant
• FIG. 8 represents a bottom view of the soleplate illustrated in FIG. 7.
• the support 2 comprises, on its outer face 21 intended to be in contact with the laundry to be ironed, a coating 3 which is substantially identical to that illustrated in Figure 6: it does not It differs only in the absence of rounded charges in the discontinuous outer enamel layer 33.
• culinary article holder made of cast iron and sheet steel.
• compositions Bl and VI As ferromagnetic flakes that can be used in the context of the present invention, it will be possible to use in compositions Bl and VI:
• Porous pigmented Bl enamel slip composition with magnetizable charges for aluminum substrates (culinary articles, insoles of irons made of aluminum or cast aluminum ).
• An enamel frit slip B 1 is prepared, the composition of which is given below in Table 1 below.
• the contents indicated are parts by weight per 100 parts by weight of frit (reference amount in the composition of the slip).
• An enamel frit slip B2 is prepared, the composition of which is given below in Table 3 below.
• a varnish composition VI is prepared, the composition of which is given below in Table 5 below.
• a pigmented enamel frit slip B3 is prepared to form a white cover enamel. Its composition is given in Table 6 below.
• Table 7 shows the composition of the F3 frit used for the white cover enamel.
• Silkscreen paste compositions (with and without rounded fillers)
• a first charge-free P3 screen-printing paste composition is prepared, the composition of which is given below in Table 8 below.
• a second composition of screen printing paste P4 is prepared with fillers, the composition of which is also given below in Table 8 below. Table 8
• the slurry B1 the composition of which is given in Table 1
• the varnish composition VI the composition of which is given in Table 2
• a layer of varnish 32 (thickness 35 ⁇ ).
• the magnetizable flakes contained in the layers of enamel 31 and varnish 32 are oriented by magnetization in certain zones of the protective coating, immediately after the application of these layers, by application of a magnetic field of 70 mT by means of two permanent magnets 51, 52 disposed under the substrate (in this case under the face of the support opposite to that which is coated), as is schematically illustrated in FIGS. 9 and 10.
• the flakes of mica thanks to their coating of magnetic iron oxide, are oriented along the field lines, that is to say the right of the magnet, and in particular substantially vertically in the areas P1 and P2 shown in FIG. 9 .
• the viscosity of the layers applied is as low as possible.
• the introduction of a small amount of a non-VOC heavy solvent such as hexylene glycol makes it possible to reduce the evaporation on spraying and offers a longer duration of application of the magnets, allowing an orientation after easier spray. Avoid any drying of the enamel layer before orienting the magnetic charges.
• the magnets can be applied until the final drying of the coating, to consolidate the orientation. This mode is particularly recommended if you want to get a decor with a clear perception of relief.
• the flakes tend to orient themselves perpendicular to the support (that is to say, a majority of them have an angle of inclination relative to the support between 45 and 90 °) where the field lines are perpendicular to the support 2, that is to say in the zone C, corresponding to the zone 5 (FIG. 13C),
• EXAMPLE 2 Production of a protective coating according to the invention on the cap of an iron soleplate.
• the orientation of the magnetizable particles is carried out, as for Example 1, by applying a magnetic field of 70 mT by means of two permanent magnets 51, 52 arranged under the substrate (in this case under the face of the opposite support to that which is coated), as schematically illustrated in Figures 9 and 10 and actually in Figure 11.
• mica flakes thanks to their magnetic iron oxide coating, s 'orient according to the field lines, ie to the right of the magnet substantially vertically (zone C).
• FIG. 13 The observations of this scanning electron microscope (SEM) coating at the zone Z are represented by the SEM images shown in FIG. 13 (FIGS. 13a to 13c respectively showing the zones A to C).
• zone C (corresponding to reference 5 in Figures 1 to 7), which is the area between the two magnets 51 and 52 where the magnetic field lines are perpendicular to the support, is a black area, since it is perceives that little or no reflection of magnetizable particles (because of their vertical position relative to the support); zone B (corresponding to reference numeral 6 in FIGS.
• zone A which is essentially defined as the central part of magnet 51, has an average brightness (between that observed in zone B and that observed in zone C), since the magnetizable particles are oriented relative to the support an intermediate angle (greater than 20 ° but less than that observed in zone C).
• EXAMPLE 3 Production of a Protective Coating According to the Invention on the Internal and / or External Face of a Cast Iron Culinary Object Holder
• This article will usually be processed in 2 layers with 2 firings.
• Spray is applied on the inner and outer wall of a culinary article support cast steel previously blasted and degreased a first layer of glaze enamel B2 (see Tables 5 and 6) generally opaque. This layer will be fired between 800 ° C and 850 ° C for 4 to 12 minutes.
• ferromagnetic flakes it is possible from the first layer to use ferromagnetic flakes: if this is the case, their orientation will be facilitated if the magnets are applied when the enamel is still liquid, or before drying and baking. Drying will maintain the orientation of the flakes subjected to the magnetic fields of the magnets.
• the slip of enamel cover B3 is applied.
• the thickness of this second layer will be 100 to 200 ⁇ m. This layer will make it possible to obtain the mechanical reinforcement related to the orientation of the flakes during the application of the magnetic field. This step will be preferred and facilitated when the slip of enamel is still liquid (favored mobility). This second firing will take place between 750 ° C and 820 ° C for 4 to 12 minutes.
• enamels described above in the case of cast iron metals for culinary applications or small household appliances can be applied either within the article or outside the article. Their strengthening of the mechanical properties can take place inside the article (multiple contact with utensils: whip, knife, spatula %) or outside the article (hob, sink, grill). oven ).
• the coating described above has a significant improvement over the same coating free of magnetizable flakes oriented in the slip B3.
• the optimization of the resistance to chipping is beneficial for example by the shock of a metal utensil during a conventional use.
• COMPARATIVE EXAMPLE 4 Production of a Protective Coating on the External Face of an Iron Sole Free of Magnetizable Particles
• a protective coating comprising an enamel layer 31, on which is deposited a layer of varnish 32, then a layer of screen-printed enamel 33.
• the protective coating of comparative example 1 differs from that of example 1 in the absence of magnetizable flakes in the layers of enamel 31, varnish 32, and serigraphic enamel layer 33.

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