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
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/07—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing phosphates
  • C23C22/08—Orthophosphates
  • C23C22/20—Orthophosphates containing aluminium cations
• • 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
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/07—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing phosphates
  • C23C22/08—Orthophosphates
  • C23C22/18—Orthophosphates containing manganese cations
• • 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
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/73—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals characterised by the process
  • C23C22/74—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals characterised by the process for obtaining burned-in conversion coatings
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
  • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
  • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
  • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
  • H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
  • H01F1/147—Alloys characterised by their composition
  • H01F1/14766—Fe-Si based alloys
  • H01F1/14775—Fe-Si based alloys in the form of sheets
  • H01F1/14783—Fe-Si based alloys in the form of sheets with insulating coating
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
  • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
  • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
  • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
  • H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
  • H01F1/16—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of sheets
  • H01F1/18—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of sheets with insulating coating

Definitions

• the present invention relates to aqueous compositions which are suitable for coating grain-oriented steel ("GO", “grain oriented steel”), which is used, for example, in transformers.
• GO grain-oriented steel
• Grain-oriented electrical steel sheet is used for the production of transformers, dynamos and high-performance generators in order to ensure the required soft magnetic properties.
• Grain-oriented steel is essentially a low-carbon steel (carbon content of approx. 0.01% to approx. 0.1%), which has a high silicon content of approx. 2.5% to approx. 7.0%.
• the grain orientation is achieved through selected rolling, annealing and tempering steps. Sheets of this steel are ultimately dipole-oriented and magnetizable in the rolling direction. Such steel sheets are often produced as steel strips with a thickness of approx. 0.2 to approx. 0.4 mm. In order to protect them from corrosion until they are processed (transport, punching, etc.), they are usually provided at the factory, i.e. Immediately after their production, the sheet is provided with an approximately 1 to 2 ⁇ m layer of Mg silicate ("forsterite"). This is done by coating with MgO, which reacts in an annealing process (“hood annealing”) with surface silicon from the steel to form silicate. This coating is hereinafter referred to as the "basecoat”.
• the primer coating provides sufficient temporary protection against corrosion and is essentially electrically insulating.
• compositions for coating grain-oriented steel which can be used directly without mixing several components and, moreover, can be stored for a longer period of time without quality restrictions.
• the storage-stable composition according to the invention makes it possible to protect grain-oriented steel in a corrosion-resistant manner and to insulate it electrically without the composition comprising environmentally harmful metals such as chromium.
• the composition according to the invention can be applied directly to the steel or to steel primed with forsterite.
• Another aspect of the present invention relates to a method for producing an aqueous composition for coating grain-oriented steel comprising the step of mixing aluminum cation releasing compounds, manganese cation releasing compounds, dihydrogen phosphate, hydrogen phosphate and / or phosphate anion releasing compounds, colloidal silicon dioxide and optionally iron cations releasing compounds as defined in the present patent application (see claim 1).
• composition according to the invention the individual components are dissolved in water as described above. Methods for mixing such compounds with water are well described in the prior art. By mixing these components, it is possible to produce storage-stable compositions.
• Yet another aspect of the present invention relates to a method for coating grain-oriented steel comprising applying an aqueous composition according to the present invention or an aqueous one Composition preparable by a method according to the present invention.
• Another aspect of the present invention relates to grain-oriented steel, preferably grain-oriented steel sheet, obtainable by a coating method according to the present invention.
• Yet another aspect of the present invention relates to grain-oriented steel, preferably grain-oriented steel sheet, comprising a coating obtainable by applying an aqueous composition according to the present invention or an aqueous composition producible by a method according to the present invention.
• the aqueous composition according to the invention comprises aluminum cations, manganese cations, dihydrogen phosphate, hydrogen phosphate and / or phosphate anions, colloidal silicon dioxide and optionally iron cations in a certain molar ratio to one another.
• This ratio is expressed in the empirical formula (Al 2 O 3 ) 2 (MnO) 1.8-2.4 (FeO) 0-0.2 (P 2 O 5 ) 5-7 (SiO 2 ) ⁇ 30 , where the aluminum cations contained in the composition are calculated as Al 2 O 3 , manganese cations are calculated as MnO, dihydrogen phosphate, hydrogen phosphate and / or phosphate anions are calculated as P 2 O 5 , colloidal silicon dioxide is calculated as SiO 2 and optionally iron cations are calculated as FeO.
• the metal cations are preferably added to the aqueous composition as metal hydroxides, metal oxides or metal salts. Dihydrogen phosphate, hydrogen phosphate and / or phosphate anions can be incorporated into the compositions either as phosphoric acid or as phosphates.
• the abovementioned components are added to the aqueous composition according to the invention in an amount such that the empirical formula (Al 2 O 3 ) 2 (MnO) 1.8-2.4 (FeO) 0-0 , 2 (P 2 O 5 ) 5-7 (SiO 2 ) 30-100 , preferably (Al 2 O 3 ) 2 (MnO) 1.8-2.4 (FeO) 0-0.2 (P 2 O 5 ) 5-7 (SiO 2 ) 30-80 , even more preferably (Al 2 O 3 ) 2 (MnO) 1.8-2.4 (FeO) 0-0.2 (P 2 O 5 ) 5-7 (SiO 2 ) 30-70 .
• the aqueous composition according to the invention can also comprise other metal cations (besides aluminum and manganese cations) in addition to or instead of iron cations.
• the total molar ratio of these metal cations, calculated as oxide to the other components in the composition, corresponds to that of the iron cations (see claim 1).
• This aqueous composition can be used for coating grain-oriented steel, in particular grain-oriented steel sheet.
• Grain-oriented sheet steel is susceptible to corrosion after its production, so it is coated with a primer (usually an aqueous MgO dispersion). Since this base coating can usually only insufficiently protect the steel sheet from corrosion due to micropores and macropores in the coating, it is necessary to provide the base-coated steel sheet with a further coating. This (additional) coating can be achieved by the aqueous composition according to the invention.
• Pores in the base coat can be detected, for example, by applying a dilute permanganate solution. Depending on the extent of the porosity, such a solution is discolored depending on the time and concentration, triggered by the access of Mn VII ions to the steel surface exposed at certain points and their oxidation products (associated with the reduction of Mn VII to Mn II / III). If such a porosity is determined in such a test, this deficiency can also be remedied by means of the coating or composition according to the invention. The pores in the first coating are closed and at the same time sustainable corrosion protection is established, which is also characterized by excellent electrical insulation.
• the aqueous composition of the present invention forms a highly effective corrosion protection based on a dense layer of silicates and phosphates.
• This The coating also has the following properties: resistance to hydrolysis, resistance to annealing up to 1000 ° C, electrical insulation, good adhesion to the base coating (forsterite layer) or directly to a steel surface, no stickiness under processing conditions, attenuation of the sound waves caused by magnetostriction oscillation in later use ( with transformers "Transfomatorhummen").
• the coating agents described in the prior art which are usually mixed shortly before their use and are not available as a ready-to-use composition, are characterized by comparable properties, even if they provide a significantly poorer quality in terms of the properties mentioned above compared to the coating according to the invention .
• An example in this context is the DE 2247269 mention in which such coating agents are disclosed.
• a special feature of the compositions described therein is that they contain chromate in order to ensure the desired anti-corrosion properties of the silicate / phosphate matrix used.
• Cr VI compounds are increasingly undesirable, also legally, because of their harmful effects on human health and the environment.
• aqueous compositions according to the invention are characterized in that they are chromium-free, stable in storage (at least three months at a room temperature of 22 ° C), one-component and the coatings that can be produced with it have the necessary physical properties described above.
• the Al 2 O 3 : MnO ratio is 1: 1 to 1: 1.2, even more preferably 1: 1.1 to 1: 1.2.
• the SiO 2 : P 2 O 5 ratio should preferably be more than 4.3. According to a preferred embodiment of the present invention, this ratio is more than 4.3 and less than 16.7, even more preferably more than 4.3 and less than 13.3. If the SiO 2 : P 2 O 5 ratio is less than 4.3, there could be problems with the hydrolysis and / or corrosion resistance of the coating that can be produced with the composition according to the invention.
• the Al 2 O 3 : P 2 O 5 ratio is preferably greater than 1: 2.5 in order to ensure sufficient resistance to SiO 2 colloids.
• the proportion of P 2 O 5 must be adjusted stoichiometrically.
• part of the manganese content in a second coating (which can be produced using the composition according to the invention) can be replaced or supplemented by iron oxide.
• Mn-Fe mixed phosphates are particularly sparingly soluble and thus make a positive contribution to the homogeneity of the base coating (pore closure) and to the stability of the second coating (hydrolysis resistance).
• this can be optimal by using of iron (II) oxalate, which decomposes thermally in a known manner at over 600 ° C (in addition to the desired metal oxide in gases (CO and CO 2 )) and thus defects in the base coat not only due to iron oxide or iron phosphate fills, but already partially oxidized steel surfaces are reduced again.
• the number of SiO 2 in the empirical formula according to claim 1 is 30 to 100, preferably 30 to 80, even more preferably 30 to 70.
• the number of P 2 O 5 in the empirical formula is 5.4 to 6.8, preferably 5.6 to 6.6, even more preferably 5.8 to 6.4.
• the aluminum cations, manganese cations, dihydrogen phosphate, hydrogen phosphate and / or phosphate anions and optional iron cations present in the composition according to the invention can be introduced into it by mixing various salts, hydroxides, oxides and / or acids with water. According to a preferred embodiment of the present invention, the composition according to the invention therefore comprises aluminum hydroxide and / or aluminum phosphate.
• Manganese cations are preferably added to the aqueous composition according to the invention as manganese (II) oxide, manganese (II) oxalate and / or manganese (II) hydroxide.
• iron cations are added as iron (II) oxide and / or iron (II) oxalate to the aqueous composition according to the invention, iron (II) oxalate being particularly preferred.
• the composition according to the invention can comprise other or further metal cations which are capable of forming poorly soluble phosphates or pyrophosphates.
• the composition according to the invention preferably contains metal cations, calculated as metal oxides, minus aluminum and Manganese cations in the same stoichiometric ratio to one another as given in the empirical formula according to claim 1 for iron cations, calculated as iron oxide.
• colloidal silicon dioxide contained in the aqueous composition is free of charges.
• colloidal silicon dioxide comprising charged metal ions or the like are less preferred or not desirable.
• the colloidal silicon dioxide in the aqueous composition according to the invention is therefore essentially free of surface charges.
• the colloidal silicon dioxide comprises silicon dioxide particles, preferably spherical silicon dioxide particles, in the size between 5 and 80 nm, preferably between 5 and 60 nm, even more preferably between 5 and 40 nm.
• the silicon dioxide particles in the composition according to the invention preferably have a specific surface area of 400 to 450 m 2 / g at a size of 5 nm, a specific surface area of 180 to 200 m 2 / g for a size of 15 nm and a size of 20 nm a specific surface of 130 to 150 m 2 / g, with a size of 25 nm a specific surface of 100 to 120 m 2 / g, with a size of 30 nm a specific surface of 90 to 110 m 2 / g, with a A size of 35 nm has a specific surface area of 60 to 70 m 2 / g, with a size of 40 nm a specific surface area of 40 to 50 m 2 / g.
• the ratio of the sum of the specific surface area of the particles of colloidal silicon dioxide to the total number of moles of all metal oxides is 1: 10,000 to 1: 200,000, preferably 1: 20,000 to 1: 150,000, even more preferably 1: 25,000 to 1: 100,000, more preferably 1: 30,000 to 1: 80,000.
• the molar ratio of the sum of the metal ions, calculated as their oxides, in particular the sum of the aluminum cations, calculated as Al 2 O 3 , and manganese cations, calculated as MnO, to silicon dioxide in the composition 1: 6, 5 to 1: 26.5, preferably 1: 6.8 to 1:20, even more preferably 1: 7.5 to 1:18, even more preferably 1: 8 to 1:16.
• the molar ratio of the sum of the metal ions, calculated as their oxides, in particular the sum of the aluminum cations, calculated as Al 2 O 3 , and manganese cations, calculated as MnO, to silicon dioxide in the composition is preferably 1: 9 up to 1:13, more preferably 1:10 to 1:12, if a surface is coated with the aqueous composition with a layer thickness of less than 1.5 ⁇ m, preferably less than 1 ⁇ m.
• the molar ratio of the sum of the metal ions, calculated as their oxides, in particular the sum of the aluminum cations, calculated as Al 2 O 3 , and manganese cations, calculated as MnO, to silicon dioxide in the composition is preferably 1:10 up to 1:14, even more preferably 1:11 to 1:13, if a surface is coated with the aqueous composition with a layer thickness of 2 to 10 ⁇ m, preferably 2 to 5 ⁇ m.
• the aqueous composition according to the invention has a solids content between 10% and 70%, preferably from 20% to 60%, even more preferably from 25% to 40%.
• Another aspect of the present invention relates to a method for producing an aqueous composition for coating grain-oriented steel comprising the step of mixing aluminum cation releasing compounds, manganese cation releasing compounds, dihydrogen phosphate, hydrogen phosphate and / or phosphate anion releasing compounds, colloidal silicon dioxide and optionally iron cations releasing compounds as defined above.
• Ion-releasing compounds are compounds that are able to release ions in water (e.g. metal ions such as aluminum). Ion-releasing compounds can be salts, oxides, oxalates or hydroxides.
• Yet another aspect of the present invention relates to a method for coating grain-oriented steel comprising the application of an aqueous composition according to the present invention or an aqueous composition producible by a method according to the present invention.
• the grain-oriented steel is primed with forsterite.
• the grain-oriented steel to be coated can comprise a base coating in order to protect it from rapid corrosion after its production.
• the basecoat preferably comprises forsterite.
• the grain-oriented steel has the shape of a sheet.
• Such sheets can be used, for example, to manufacture transformers.
• the aqueous composition is used in an amount from 1 to 50 g / m 2 , preferably from 2 to 40 g / m 2 , even more preferably from 3 to 30 g / m 2 , even more preferably from 4 to 20 g / m 2 , applied to the grain oriented steel.
• the aqueous composition is preferably applied to grain-oriented steel by means of a dipping process, rolling process or spraying process.
• the grain-oriented steel coated with the aqueous composition is treated at a temperature of 500 ° C to 900 ° C, preferably 600 ° C to 850 ° C.
• the aqueous composition is applied to the grain-oriented steel in a layer thickness of 100 nm to 20 ⁇ m, preferably 200 nm to 10 ⁇ m.
• Another aspect of the present invention relates to grain-oriented steel, preferably grain-oriented steel sheet, obtainable by a method according to the present invention.
• Yet another aspect of the present invention relates to grain-oriented steel, preferably grain-oriented steel sheet, comprising a coating obtainable by applying an aqueous composition according to the present invention or an aqueous composition producible by a method according to the present invention.
• Example 1 Preparation of aqueous compositions for coating grain-oriented steel
• Primed GO sheet ie a grain-oriented steel sheet coated with forsterite
• compositions 2 to 9 By adapting the stoichiometric ratios of the components listed above, the following additional compositions (compositions 2 to 9) could be produced: Composition 2 (Al 2 O 3 ) 2 (MnO) 2.1 (FeO) 0.18 (SiO 2 ) 75 (P 2 O 5 ) 6.2 Composition 3 (Al 2 O 3 ) 2 (MnO) 2.2 (FeO) 0.18 (SiO 2 ) 49 (P 2 O 5 ) 6.3 Composition 4 (Al 2 O 3 ) 2 (MnO) 2.0 (FeO) 0.2 (SiO 2 ) 32 (P 2 O 5 ) 6.5 Composition 5 (without iron oxide) (Al 2 O 3 ) 2 (MnO) 2.2 (SiO 2 ) 55 (P 2 O 5 ) 6.1 Composition 6 (Al 2 O 3 ) 2 (MnO) 1.75 (FeO) 0.15 (SiO 2 ) 55 (P 2 O 5 ) 6.2 Com
• compositions 2 to 7 were also applied to a primed GO sheet in an amount of 5 g / m 2 , dried briefly in air and baked at 820 ° C. for 60 seconds.
• Composition No. SiO 2 P 2 O 5 Al 2 O 3 : MnO Al 2 O 3 : P 2 O 5 m 2 SiO 2 per Me x O y *) Me x O y : - SiO 2
• Molecular formula 1 8.41 1: 1.1 1: 3.15 47,000 1: 12.05 (Al 2 O 3 ) 2 (MnO) 2.2 (FeO) 0.2 (SiO 2 ) 53 (P 2 O 5 ) 6.3 2nd 12.10 1: 1.05 1: 3.10 68,000 1: 17.52 (Al 2 O 3 ) 2 (MnO) 2.1 (FeO) 0.18 (SiO 2 ) 75 (P 2 O 5 ) 6.2 3rd 7.78 1: 1.1 1: 3.15 44,000 1: 11.19 (Al 2 O 3 )
• the comparative compositions 1 to 4 were - as described in Example 1 - applied to a primed GO sheet in an amount of 5 g / m 2 , dried briefly in air and baked at 820 ° C. for 60 seconds.
• Example 3 Testing of the compositions and coatings from Examples 1 and 2
• One aim of the invention is to provide storage-stable aqueous compositions in order to ensure sufficient user-friendliness. For this reason, the stability of the aqueous composition was evaluated. It was observed over a longer period of time whether the aqueous composition remained stirrable and whether particles settled. Both properties are important for the storage stability of the compositions.
• a decisive quality criterion of compositions that are used for coating grain-oriented steel is their ability to protect the coated steel from corrosion.
• a stack of coated, water-wetted sheet metal samples whose basecoat comprising Mg-silicate (forsterite) was coated with the compositions according to Examples 1 and 2, was tightly packed in a water- and vapor-impermeable film and stored for 8 hours at 90 ° C stored in the heating cabinet. The surface of the coated metal sheets was then visually assessed.
• Inclusions in the finished coating can also represent a relevant criterion for the quality of the composition according to the invention. Any inclusions were visually recorded and assessed.
• bubbles in the finished coating on the sheet metal are generally undesirable, since bubbles are precursors for subsequent signs of corrosion. Blistering can be assessed visually.
• compositions 1 to 5 and 7 have a long shelf life of more than three months and the coatings produced with them have high hydrolysis resistance and extremely low susceptibility to corrosion.
• the comparative compositions from the prior art have a low storage stability in a ready-to-use mixture.
• the hydrolytic stability of the coatings produced therewith is also not optimal.
• Composition 6 also shows that a lower molar ratio between Al 2 O 3 and MnO (2: 1.75) in the composition leads to a lower storage stability.

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• 2019
  • 2019-02-06 EP EP19155700.8A patent/EP3693496A1/fr not_active Withdrawn
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