Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/10—Electroplating with more than one layer of the same or of different metals
  • C25D5/12—Electroplating with more than one layer of the same or of different metals at least one layer being of nickel or chromium
  • C25D5/14—Electroplating with more than one layer of the same or of different metals at least one layer being of nickel or chromium two or more layers being of nickel or chromium, e.g. duplex or triplex layers
• • 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
  • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
  • C23C28/02—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material
• • 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
  • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
  • C23C28/02—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material
  • C23C28/021—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material including at least one metal alloy layer
• • 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
  • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
  • C23C28/02—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material
  • C23C28/023—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material only coatings of metal elements only
• • 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
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/48—After-treatment of electroplated surfaces
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D7/00—Electroplating characterised by the article coated
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D9/00—Electrolytic coating other than with metals
  • C25D9/04—Electrolytic coating other than with metals with inorganic materials
  • C25D9/08—Electrolytic coating other than with metals with inorganic materials by cathodic processes
  • C25D9/10—Electrolytic coating other than with metals with inorganic materials by cathodic processes on iron or steel
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/12—Electroplating: Baths therefor from solutions of nickel or cobalt

Definitions

• the subject of the invention is a process for coating a substrate with an anticorrosion protective layer, comprising the following work steps: providing a substrate to be coated, coating the substrate with a nickel-based preparation, coating of the substrate with a preparation based on trivalent chromium.
• the invention also relates to a household appliance accessory for use in the gastronomic field, with a body structure made substantially of steel, with a coating comprising chromium, with an oily coating, wherein the body structure has at least one solder joint.
• hexavalent chromium (CrVl) in a chrome plating step for both metal and plastic objects, in the form of finished or semi-finished products, i.e. say having undergone at least one transformation step and having a final shape, in order to give them an improved appearance and to give them better resistance to corrosion.
• the term hexavalent chromium CrVl or chromium(VI) oxide designates in the context of the present invention the 6th oxidation state of chromium.
• a chrome plating operation consists in covering a chrome substrate with a layer of greater or lesser thickness, depending on whether a layer for decorative purposes (decorative chrome plating) or as protection against wear and scratches (hard chrome plating) is desired.
• hexavalent chromium is dangerous for human health, and is, among other things, carcinogenic. It is planned to prohibit the use of hexavalent chromium in the near future, in particular for chromium plating operations.
• chrome parts are used for applications with relatively high or low temperatures compared to ambient temperatures, such as in ovens or refrigeration systems.
• some applications require food compatibility and/or corrosion resistance in a saline environment
• the invention is based on the technical problem of improving the treatment processes from trivalent chromium known hitherto.
• the present invention is based on the technical problem of providing a process making it possible to produce a coating that is not or only slightly toxic to human health, while improving the corrosion resistance of the coated product.
• a process for coating a substrate with an anticorrosion protective layer comprising the following work steps: providing a substrate to be coated, coating the substrate with a preparation to nickel base, coating the substrate with a preparation based on trivalent chromium, the method being characterized by a step of coating the substrate with a preparation comprising a mineral oil-based additive.
• the treatment of a semi-finished product such as for example a strip or a reel of material with an oil in order to guarantee protection of said material for transport to a pre-production storage location is already known.
• the materials or semi-finished products thus treated are generally degreased downstream of a transformation step into a finished product, i.e. the composition or surface of the finished products obtained after the transformation step is substantially free of oil.
• a mineral oil-based additive in a post-chroming treatment step of a finished product makes it possible to improve the anti-corrosion effect of a surface treated with trivalent chromium.
• the anti-corrosion resistance of metal parts having at least one weld joint which are particularly sensitive to corrosion is increased compared to an identical part which has not undergone a final oil-based treatment, while guaranteeing good temperature resistance and non-toxicity when in contact with food.
• the corrosion resistance of substrates which have been treated according to the process of the invention have a corrosion resistance at least as pronounced as substrates which have been treated with hexavalent chromium.
• the claimed process improves the corrosion resistance of the treated substrate, preserves the decorative effects of a chromium treatment, while reducing the harmful and toxic effects of processes based on the use of hexavalent chromium .
• Coating the substrate with nickel prior to the coating step with trivalent chromium provides increased protection against corrosion and scratching of the substrate, especially the surface of the substrate.
• the coating with chrome gives a shiny appearance to the treated substrate and prevents yellowing of the underlying nickel.
• the combination of nickel with chromium provides access to a wide range of colors for the final appearance of the coated substrate, while guaranteeing good resistance to the chosen colorimetry.
• a substrate to be coated according to the invention is, preferably and in contrast to, for example, a strip or a wire, an intermediate or semi-finished product, a product having undergone most of the processing steps provided for obtaining from a finished product .
• the substrate to be coated preferably already has at least its final geometry, and has preferably undergone all the welding steps provided before the application according to the invention.
• the process according to the invention corresponds to a final stage of preparation before the sale, the packaging or even the storage of the substrate then coated.
• a substrate according to the invention can, for example, be a milled, turned, stamped, punched, extruded or other part, in particular in the form of a cable, wire, housing, component or part for gastronomy, packaging, automotive, aviation, medicine, for furniture parts or others.
• mineral oil-based additive designates within the scope of the invention any sort of water-soluble organic additive, which has the property of not forming a film on the surface of a bath when it is in solution in water.
• the additive used is preferably a concentrate intended for the protection against corrosion of ferrous materials.
• the additive used can be solvent-free and/or nitrite-free.
• the substrate to be coated has a junction by welding.
• the method according to the invention is particularly advantageous when applied to such substrates: it has in fact been observed that the preparation comprising a mineral oil-based additive infiltrates into any interstices present at the solder joints, thus making it possible to prevent the formation of corrosion in an increased way.
• the solder joint can join parts of the substrate together, where the parts of the substrate can be of plastic or metallic material.
• the joint by welding can be a spot weld or a longitudinal weld, where the term “point” of weld is equivalent to the technical term specific to the usual welding processes.
• the substrate to be coated is an object at least partly based on metal, in particular based on a ferrous metal, more particularly based on steel.
• a substrate of this type is, due to the possible presence of iron in its composition, susceptible to corrosion. For this reason, the claimed method is particularly advantageous for this type of substrate. Furthermore, a substrate treated according to this implementation of the method will resist both hot and cold, while being protected against breakage, deformation or corrosion. As a result, the longevity of the finished products resulting from the treatment is increased.
• the substrate to be coated may consist essentially of one of the elements listed above or else have a surface layer consisting essentially of one of these same elements.
• a substrate within the meaning of the invention can be a metal part intended for use in different fields, such as household appliances, automobiles, aeronautics, packaging, even gastronomy in general.
• a substrate within the meaning of the invention may for example take the form of a metal accessory for a household appliance, or of a grid to accommodate containers such as hot saucepans.
• the process described can be applied, for example, to a perfume bottle stopper or any other high-quality metal packaging requiring anti-corrosion protection.
• the method according to the invention can be applied for example to a car grille, a bicycle frame, an aircraft door, a boat part or any other part for which corrosion protection would be a significant advantage.
• an implementation of the method provides that the substrate to be coated is an accessory for a household appliance intended for use in connection with food, in particular a trellis, a grid or a metallic accessory.
• Hexavalent chromium proves to be dangerous for human health and contact of an object treated with this chemical species with food intended for consumption is likely to promote carcinogenic consequences.
• the proposed method is therefore particularly preferable to the methods known hitherto, with the aim of replacing the use of the dangerous chromic species.
• a substrate according to this implementation can be provided for use in the industrial gastronomic field and/or in a particular household.
• a substrate can, for example, be a grid or step for a household oven, a retaining or support device to be integrated into the layout of a refrigerator or even a grid for a cooking appliance such as a barbecue, a cooking basket or weighing scale for a kitchen appliance, a part of a coffee-making machine, or even an air filter grid.
• the substrate to be coated can be any kind of part having undergone a nickel and trivalent chromium coating step, and having undergone an assembly by welding.
• the treated substrate is an object at least partly based on plastic material.
• a substrate may consist substantially of plastic material or have a surface layer of plastic material.
• the process described here can therefore be applied to a wide range of products, which allows better profitability and a relatively high return on investment of the processing chain set up for the implementation of the process.
• a perfume bottle cap, a toy part, a non-structural motorcycle or car part can be treated by the method described herein.
• the step of coating the substrate with a preparation comprising a mineral oil-based additive is carried out as a hot rinse, where the oil-based preparation is a solution comprising demineralized water and water-soluble mineral oil, in particular with a concentration ranging from 2 parts mineral oil-based additive per 10,000 parts demineralized water to 2.5 parts mineral oil-based additive per 10,000 parts demineralized water.
• This concentration range for the coating bath with mineral oil allows a compromise between the maintenance of the bath in the production line, and therefore an optimization of production costs, and the guarantee of a coating with an anti-corrosion effect. sufficient for the standards imposed in general.
• a higher concentration of additive in the preparation i.e. an amount of mineral oil-based additive relative to the amount of demineralized water higher than 2.5 parts of mineral oil-based additive of mineral oil to 10,000 parts of demineralised water, leads to rapid degradation of the coating bath and therefore requires frequent emptying.
• an additive concentration less than 2 parts mineral oil-based additive to 10,000 parts deionized water the substrate is coated with a thin layer of oil, which may be insufficient for adequate substrate holdout corrosion resistance tests.
• the method described above is preferably carried out in such a way that the step of coating the substrate with a preparation comprising a mineral oil-based additive is carried out at a target temperature ranging from 40°C to 60°C. C, in particular ranging from 45°C to 55°C, preferably ranging from 47.5°C to 52.5°C, more preferably at a target temperature of 50°C.
• the part dipped in the bath containing the preparation is heated, preferably until the target temperature is reached.
• Heating to a target temperature within one of the indicated temperature ranges promotes wetting of the surface of the substrate immersed or soaked in the bath with the preparation comprising a mineral oil-based additive.
• the recommended heating of the bath also promotes the homogeneity of the preparation comprising the additive and the demineralised water. In this way, the probability of covering the substrate to be coated is improved by the proposed implementation.
• a recommended implementation of the method provides that, for the step of coating the substrate with a preparation comprising a mineral oil-based additive, the substrate to be coated is exposed to the oil-based liquid preparation for a duration of at least 2 minutes, preferably with an exposure time ranging from 2 to 8 minutes, all the more preferred with an exposure time ranging from 2 to 5 minutes, in particular with an exposure time ranging from 2 to 4 minutes, more particularly with an exposure time ranging from 2.5 minutes to 3 minutes.
• a processing time with a value within one of the proposed ranges is a compromise between a processing time corresponding to a lower cost of production of coated substrates and a minimum processing time for sufficient coating of the substrate with the preparation comprising an additive. based on mineral oil.
• such an exposure time allows the substrate to reach the temperature of the preparation bath comprising a mineral oil-based additive, and to fully benefit from the wetting effect provided by the temperature of the bath.
• the exposure time is recommended to choose the exposure time according to the thickness and / or the volume of the substrate: for a solid substrate having a large volume, it is wise to choose a relatively long exposure time, so that the substrate reaches a temperature close to that of the bath. For a thin or thin-walled substrate, a relatively short time closer to 2 minutes can be chosen, thus reducing production costs.
• the exposure time can also be chosen according to the material making up the substrate to be coated, in particular according to the thermal conductivity of the substrate.
• a steel substrate in the form of a household oven grid can have, immediately on leaving the bath with the preparation comprising the additive to mineral oil base, a temperature of or close to 50°C and its surface is coated with a thin layer of the preparation comprising a mineral oil-based additive.
• a preferred implementation of the method provides for a drying step to follow the step of coating the substrate with a preparation comprising a mineral oil-based additive.
• Such a drying step allows evaporation of the demineralized water from the preparation layer deposited in the previous step.
• the substrate is preferably coated with nickel, chromium and demineralised oil.
• the drying step be carried out with a target temperature in the temperature range from 50°C to 110°C, preferably from 60°C to 100°C, in particular from 70°C to 90°C, more particularly ranging from 75°C to 85°C, more particularly a target temperature of 80°C.
• This heating step allows at least partial evaporation of the demineralized water and drying of the coated substrate, for example for subsequent storage, while avoiding degradation of the mineral oil and its anticorrosive properties.
• the temperature range in which the target heating temperature is located is preferably chosen prior to the implementation of the method, depending on the geometry of the substrate to be coated and the planned subsequent storage mode.
• a target temperature of 80° C., for example, is particularly suitable for a grid of a household appliance oven to be coated, which is intended to be stored in a cardboard box.
• the drying step prefferably has a duration ranging from 5 to 8 minutes, in particular from 6 to 7 minutes, so that at the end of the drying the demineralized water is evaporated and that it does not remains more than mineral oil on the chrome surface of the substrate.
• the coated substrate is ready for use in the gastronomic field and/or can be used in direct contact with food.
• the substrate treated with the process is a ready-to-use finished product and meets the usual standards for its use in the gastronomic field, in particular sufficient corrosion resistance and compatibility with acceptable foods according to the standards in place. .
• the substrate treated according to the invention has been tested according to the applicable standards, in particular according to the recommendations of standard NF EN 13130-1 of August 2004, of annex V of European Union regulation n ° 10/2011 of January 14, 2011, of the practical guide of the European Directorate for the Quality of Medicines and Health Care (EDQM) "Metals and Alloys", of the methodological document of the Directorate General for Competition, Consumption and the Repression of Fraud (DGCCRF)- "Metals and Alloys", and Regulation (EC) No. 1935/2004 of the European Parliament and of the Council of October 27, 2004 concerning materials and objects intended to come into contact with foodstuffs and repealing directives 80 /590/EEC and 89/109/EEC.
• EQM Quality of Medicines and Health Care
• a particular implementation of the method provides that a step of passivation by electrolysis follows the step of coating with a preparation based on trivalent chromium and precedes the step of coating the substrate with a preparation comprising an oil-based additive. mineral.
• hexavalent chromium for a coating has the effect of passivating the coated surface, i.e. contributes to improving the corrosion resistance of said surface.
• the passivation effect and therefore corrosion inhibition is largely lost.
• the invention proposes an intermediate step, that is to say after the deposition of trivalent chromium and before the deposition of oil on the surface of the substrate to be protected, of passivation by electrolysis.
• the electrochemical passivation of a steel part has the effect of eliminating the ferrous part on the surface of the part and of oxidizing the metallic chromium present in the part into chromium oxide.
• a preparation based on demineralised water to which additives, in particular based on trivalent chromium salts, are added.
• a first additive with a concentration ranging from 23 to 27 ml per liter of preparation a second additive containing trivalent chromium salts with a concentration ranging from 12 to 18 ml per liter of preparation and a third additive with a concentration ranging from 0.3 to 0.7 ml per liter of preparation can be provided.
• the first additive is consumed by entrainment of the bath, the second additive based on trivalent chromium salts is used for assembling the bath and the third additive is intended to limit the formation of impurities in the passivation bath.
• the first additive is preferably in liquid form
• the second additive and the third additive are preferably each in solid form.
• a range for the working temperature ranging from 25°C to 30°C
• a working range for the pH of the preparation ranging from 9.3 to 9.8
• a range ranging from 120 to 180 seconds are preferred. for this passivation step.
• An example of implementation for the passivation step consists of exposure to the passivation preparation for a period ranging from 2 to 4 minutes, preferably ranging from 2.5 to 3 minutes in an electrolysis bath, where a anode and a cathode are provided and separated by a distance in the range of 100 to 180 mm, preferably a distance of about 120 mm.
• a household electrical appliance accessory for use in the gastronomic field, with a body structure consisting substantially of steel and with a coating based on trivalent chromium , where the body structure has at least a solder joint, characterized in that an oily coating is provided, and in that the distribution of the oily coating is substantially limited to the area of the at least one solder joint.
• An accessory according to the invention not only has the advantage of having an improved appearance provided by the combined coating of nickel and chromium while being harmless to human health, but also a sufficiently good resistance to corrosion to compete with a coating based on hexavalent chromium.
• the welded joints of the structure of the accessory are, in general, more vulnerable to corrosion than the solid surfaces of this same structure.
• This vulnerability is explained by variations in surface texture such as cracks, crevices or material irregularities at weld joints, which are conducive to the formation of corrosion. Thanks to the coating of the welding surfaces or at least of the welding joints of the accessory with an oily coating, these irregularities in material and / or texture are partly filled by the oil, thus preventing the onset of corrosion by contact with air or water.
• An accessory within the meaning of the invention is preferably a finished product, in contrast to a semi-finished product which requires at least one additional processing step before it can be used by an end consumer.
• the accessory can for example take the form of a rack for a household appliance oven, a cooking basket for a food processor, or any other example included in the definition for a substrate to be coated that can be used in the gastronomic field such as quoted earlier.
• a substrate to be coated and in the form of a steel grid for a household oven is loaded onto a transport support driven by a robot, then driven by the robot to a processing line.
• the overall processing line comprises a preparation line and a deposit line proper, the preparation line preceding a deposit line.
• the grid loaded on the robot is taken to the first bath of the preparation line for degreasing, the purpose of which is to rid the grid of any greasy traces accumulated during the processing, transport and/or storage stages of the grid. before the implementation of the coating process.
• the substrate undergoes the following preparation steps in order, for each of which a tank containing a corresponding preparation is provided: a) rinsing, b) acid pickling, c) rinsing, d) electrolytic degreasing and / or degreasing under current electric with a rectifier then e) rinsing.
• the household oven rack thus prepared is taken by the robot to the deposition line also comprising a series of successive treatment steps, arranged as follows: f) depassivation bath, g) rinsing, h) bath with a preparation to nickel base for a semi-bright nickel coating i) bath with a nickel-based preparation for a bright nickel coating, j) rinsing, k) activation bath to prepare the surface of the substrate to receive chrome, l] spray rinsing, m] bath with preparation based on trivalent chromium, n] rinsing by soaking, rinsing by spraying, passivation bath under current, o] hot rinsing with preparation comprising an additive based on mineral oil, and drying.
• the rinsing steps are carried out with demineralized water to guarantee as much as possible an electrochemical neutrality of the wet surface of the substrate to be coated, in this case the grid of a household oven.
• the bath with a nickel-based preparation for a semi-bright nickel coating in position h) of the deposition line has a boric acid content in the range from 45.0 to 50.0 g/L, a content in nickel chloride ranging from 55.0 to 65.0 g/L, a nickel content ranging from 65 to 80 g/L and a nickel sulphate content ranging from 240 to 300 g/L.
• the bath with a nickel-based preparation for bright nickel coating in position i] of the deposition line a boric acid content in a range from 45.0 to 50.0 g/L, a chloride content of nickel ranging from 55.0 to 65.0 g/L, a nickel content ranging from 70 to 80 g/L and a nickel sulphate content ranging from 250 to 300 g/L.
• the substrate to be coated here the household oven rack, has a total nickel coating of between 12 and 19 ⁇ m in thickness, which can be distributed for example between approximately 8 ⁇ m in thickness of semi-bright chrome and about 7 ⁇ m of bright nickel.
• the trivalent chromium bath has a target temperature within a range of 50 to 55°C, a current density within a range of 8 to 12 Amps per dm 2 , and an anode to cathode distance within a range from 100 to 180 mm, preferably a distance of about 120 mm.
• the household oven rack with a layer of nickel is soaked for a total time ranging from 4 to 5 minutes in the trivalent chromium bath.
• the household oven grid has a layer of chromium with a thickness ranging from 2 to 4 ⁇ m, preferably ranging from 2 to 3 ⁇ m thick.
• bath within the meaning of the above explanations designates a quenching step in one or more liquids distributed in one or more tanks, where the liquids have a similar composition.
• a “bath of trivalent chromium” can for example be carried out in two quenches, each in an oven containing a liquid preparation of similar composition, to lengthen the total quenching time of the substrate to be coated while avoiding a slowdown overall processing chain.
• the concentration of the respective preparations of the tanks corresponding to the successive baths is monitored and adjusted regularly, in order to guarantee that the contents are included in the predefined tolerance ranges.
• the treated household oven grid is unloaded from the robot and the transport support is freed from any layers of products accumulated during the baths. of the treatment chain, to be able to be put into service again in a new treatment cycle with a substrate free of nickel / chromium coating.
• the grid thus treated has a decorative and protective coating of nickel/chromium, the corrosion inhibiting properties of which are enhanced by a coating based on mineral oil, the latter being substantially covering the weld joints of the grid at the intersections of its hold.
• a coating based on mineral oil the latter being substantially covering the weld joints of the grid at the intersections of its hold.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Electrochemistry (AREA)
• Mechanical Engineering (AREA)
• Inorganic Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Other Surface Treatments For Metallic Materials (AREA)

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• 2022
  • 2022-03-03 EP EP22305246.5A patent/EP4239100A1/de not_active Withdrawn
  • 2022-05-30 DE DE202022103030.8U patent/DE202022103030U1/de active Active
• 2023
  • 2023-03-01 WO PCT/EP2023/055106 patent/WO2023166023A1/fr not_active Ceased
  • 2023-03-01 EP EP23707735.9A patent/EP4486933A1/de not_active Withdrawn

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