US3591468A - Method of coating metal surfaces with a fluorine-containing polymer - Google Patents

Method of coating metal surfaces with a fluorine-containing polymer Download PDF

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US3591468A
US3591468A US726350A US3591468DA US3591468A US 3591468 A US3591468 A US 3591468A US 726350 A US726350 A US 726350A US 3591468D A US3591468D A US 3591468DA US 3591468 A US3591468 A US 3591468A
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chromium plating
polymer
fluorine
chromium
plating layer
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Kazuyo Nishio
Osamu Geshi
Junichi Sako
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Daikin Industries Ltd
Toho Kasei Co Ltd
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Daikin Industries Ltd
Toho Kasei Co Ltd
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    • 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
    • B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
    • B05D5/08—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain an anti-friction or anti-adhesive surface
    • B05D5/083—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain an anti-friction or anti-adhesive surface involving the use of fluoropolymers
    • B05D5/086—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain an anti-friction or anti-adhesive surface involving the use of fluoropolymers having an anchoring layer
    • 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
    • C25D5/60—Electroplating characterised by the structure or texture of the layers
    • C25D5/605—Surface topography of the layers, e.g. rough, dendritic or nodular layers
    • 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
    • C25D5/60—Electroplating characterised by the structure or texture of the layers
    • C25D5/625—Discontinuous layers, e.g. microcracked layers
    • 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
    • C25D5/627—Electroplating characterised by the visual appearance of the layers, e.g. colour, brightness or mat appearance
    • 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
    • B05D2202/00—Metallic substrate
    • 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
    • B05D2350/00—Pretreatment of the substrate
    • B05D2350/30—Change of the surface
    • B05D2350/33—Roughening
    • B05D2350/35—Roughening by chemical means
    • 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
    • B05D2350/00—Pretreatment of the substrate
    • B05D2350/60—Adding a layer before coating
    • B05D2350/65—Adding a layer before coating metal layer
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S205/00—Electrolysis: processes, compositions used therein, and methods of preparing the compositions
    • Y10S205/917—Treatment of workpiece between coating steps

Definitions

  • a method of coating a metal surface with a fluorinecontaining polymer comprising forming a chromium plating layer on a flat or roughened metal surface under various conditions, i.e. at an optimum electric current density or an electric current density higher than said optimum electric current density, electrolytically etching the surface of said chromium plating layer by reversing the polarities of electrodes to produce a number of pits, cracks or crevices therein, coating the resultant surface with dispersion of the fluorine-containing polymer and sintering said polymer to form a continuous film of said polymer on said surface.
  • the film is anchored to said surface by portions of the polymer filling the pits, cracks or crevices.
  • the present invention relates to a novel method of coating a metal surface with fluorine-containing polymers and more particularly relates to a method of forming on a metal surface a rigidly bonded film of such fluorine-containing polymer which are poor in binding property.
  • Fluorine-containing polymers such as polyethylene tetrafiuoride, polyethylene fluorochloride and ethylene tetrafiuoride-polyethylene hexafluoride copolymer, have eXcellent chemical resistance, heat resisting property, electric property and mechanical property, but on the other hand, they are usually much inferior in binding property.
  • polyethylene tetrafluoride in particular has the advantages that it is most excellent in heat resisting property and chemical resistance, is least adhesive to other articles and has a very small frictional resistance, but on the other hand, those outstanding advantages make the binding of said polymer on metal surfaces extremely difiicult.
  • a method wherein a dispersion of fluorine-containing polymer is coated on a metal surface (by application method, dipping method or spraying method), dried and sintered.
  • the method (1) in many cases involves the steps of roughening the metal surface chemically or mechanically, applying a primer on the thus roughened metal surface, and drying and sintering said primer, before applying the dispersion of fluorine-containing polymer in order to obtain an improved binding strength between said metal surface and said polymer, and yet the binding strength of the coated polymer film thus produced is usually insuflicient for the intended purposes.
  • the method (2) has the disadvantages that the bonding surface of the fluorine-containing polymer film must be chemically treated beforehand to impart a binding property thereto and such treatment is not al Ways simple because it not only necessitates the use of dangerous chemicals and a special apparatus but also re quires a technical skill, and that the binding strength 3,591,468 Patented July 6, 1971 'ice produced between the fluorine-containing polymer and the metal surface is generally not sufficiently great and further the shape of an article to be coated is inevitably ignited because the polymer is provided in the form of In any event, these conventional methods are unsatisfactory, even when the complicacy of the process is ignored, due to the fact that the binding strength of the films formed by the methods is insufficient and therefore the use of the methods for industrial applications or for the production of daily necessaries is always accompanied 2y uneasiness at the binding strength of the resultant
  • the principal object of the present invention is to provlde a method of coating a metal surface with a fluor
  • the fluorine-containing polymer coating method comprises forming a chromium plating layer on a smooth or roughened metal surface under various conditions as Will be described later, Le. at an optimum electric current density or an electric current density higher than said optimum electric current density, electrolytically etching the surface of said chromium plating layer by reversing the polarities of electrodes to produce a number of pits, cracks or crevices therein, coating the resultant surface with a dispersion of a fluorine-containing polymer and sintering said polymer to form a continuous film of said polymer thereon.
  • a method of coating a metal surface with a fluorine-containing polymer which comprises forming a chromium plating layer on the metal surface either after or without previously roughening said metal surface mechanically or chemically, electrolytically etching the surface of said chromium plating layer by reversing the polarities of electrodes to produce a number of pits, cracks or crevices therein, coating the resultant surface with a dispersion of fluorine-containing polymer and sintering said polymer to form a continuous film of the polymer on said surface.
  • the second aspect of the present invention there is provided a method of coating a metal surface with a fluorine-containing polymer as set forth above, wherein the surface of the chromium plating layer formed on the roughened metal surface is further superposed by a chromium plating layer at a lower plating bath temperature and then the surface of the top chromium plating layer is electrolytically etched by reversing the polarities of electrodes thereby to form more complicate, finer and deeper cracks or crevices therein, and thereafter the resultant surface is coated with a dispersion of fluorine-containing polymer which is dried and sintered to form a continuous film of the polymer thereon, whereby the binding strength between the fluorine-containing polymer coating and the metal is further improved by the socalled anchor affect of the polymer filling the pits, cracks or crevices.
  • the third aspect of the present invention there is provided a method of coating a metal surface with a fluorine-containing polymer as set forth above, wherein the chromium plating operation is carried out at an electric current density higher than the electric current density optimum for the ordinary chromium plating operation so as to produce a chromium plating layer having projections thereon and then the surface of said chromium plating layer is etched electrolytically to form a number of cracks or crevices therein by reversing the polarities of electrodes, which is followed by the coating of said chromium plated layer with a dispersion of the fluorine-containing polymer and sintering said polymer to form a continuous film of the polymer on the surface.
  • the coated films obtained by the methods of the present invention set forth above are rigidly bound on the metal surface without losing various inherent properties of the fluorine-containing polymer and the binding strengths therebetwen are as great as has not been obtainable by the conventional methods.
  • the important feature of the inventive coating methods resides in the fact that according to the methods fluorine-containing polymer, such as polyethylene tetrafiuoride, which are poor in binding property, can be rigidly bound directly on a metal surface without necessitating a special treatment of the metal surface such as application of a primer.
  • a further ad vantage of the methods of this invention is that the hardness and rigidity of a metal surface can be improved greatly by the chromium plating and the surfaces of even such metals as, for example, mild steel, copper, gun metal, aluminum or aluminum alloys, which are relatively low in hardness, can be made rigid by practicing the present methods.
  • the present methods can very advantageously be used in various fields of application.
  • the above-described advantages of the present invention are of course attributed to the fact that the metal surface is coated with an electro-plated chromium. In this view, the formation of the chromium plating constitutes the most important step in the methods of the present invention.
  • the binding strength between the chromium plating and the metal surface is usually stronger when said metal surface has previously been roughened than otherwise.
  • the roughening of the metal surface can be attained by any known mechanical or chemical method, such as sand blast method, shot peening method, scratch method or chemical etching method, and in the present invention any one of these methods can be selectively used optionally as the circumstances demand. Whether the metal surface is roughened or not, the metal surface must be subjected to pre-treatments, such as treatments for the purging of oxide film, removal of fat and purging of rust, before the chromium plating operation, as is usually practiced.
  • the metal surface thus treated is coated with a chromium plating.
  • a chromium plating bath Sargent bath and a fiuoro-silicate compound bath are known and either of them can be used in the present invention.
  • the Sargent bath containing, e.g. 250 g./l. of chromic anhydride and 2.5 g./l. of sulfuric acid, is used, the plating bath temperature is suitably selected relative to the electric current density as follows:
  • Chromium plating bath Electric current temperature, C.: density, a./dm. 20 7-15
  • the thickness of the chromium plating formed may be varied optionally by adjusting the current conducting period but is usually preferably from 0.001 to 2 mm. This is because a thickness not greater than 0.001 mm. will result in an insuflicient binding strength between the metal surface and the fluorine-containing polymer, whereas a thickness not smaller than 2 mm. will result in consumption of an extremely lengthy time, which is disadvantageous economically.
  • the polarities of electrodes are reversed for the electrolytic etching of said layer.
  • the deposited layer of chromium plating is partly dissolved electrolytically leaving a number of pits, cracks, or crevices in the surface of said layer.
  • the solution velocity is at least 5 times the electrodeposition velocity, current conducting period can be much shorter than in the case of electrodeposition.
  • the number of pits, cracks or crevices per unit area is variable depending upto the temperature of the plating bath used and usually it becomes smaller as the bath temperature rises.
  • the size and depth of the pits, cracks or crevices are determined mainly by the bath temperature, electric current density and current conducting period employed for the electrodeposition of the chromium plating layer. With the current conducting period fixed, it is usual that the size and depth of the pits, cracks or crevices and the interspace therebetween become greater as the bath temperature and electric current density becomes higher. Thus it will be understood that by properly selecting the plating bath temperature and electric current density for the electrodeposition operation, pits, cracks or crevices of the desired size, depth and interspace can be obtained.
  • a glossy hard chromium plating (which will hereinafter be referred simply as glossy chromium plating) is produced by each method and the electric current density for the production of such glossy chromium plating has an optimum range as specified previously.
  • the third invention use is made of an electric current density higher than said optimum range.
  • fine projections are formed on the surface of the resultant chromium plating and a glossy surface cannot be obtained.
  • These projections which are generally referred to as frost or burning in the art, are semispherical or spherical in shape, with a part thereof having a needle-like shape.
  • the plating surface with such projections thereon presents a greyish color and would be rejected when a glossy plating is desired.
  • the present inventors have found that when the surface of such a chromium plating is etched electrolytically by reversing the polarities of electrodes opposite to those for the ordinary plating operation, thereby to dissolve the plating layer partially, pits, cracks or crevices are formed in the semispherical or spherical projections and a fluorinecontaining polymer film superposed on said plating surface will produce an extremely strong binding strength between it and the plating layer.
  • the solution velocity is at least 5 times as high as the electrodeposition velocity, the current conducting period can be much shorter than in the case of electrodeposition.
  • the number of pits, cracks or crevices per unit area is variable depending upon the temperature of the plating bath used and usually it becomes smaller as the bath temperature becomes higher.
  • the size and depth of the pits, cracks or crevices are determined mainly by the bath temperature, electric current density and current conducting period employed for the electrodeposition of the chromium plating layer. With the current conducting period fixed, it is usual that the size and depth of the pits, cracks or crevices and the interspace therebetween become g eater as the bath temperature and electric current density become higher. Thus, it will be understood that by properly selecting the plating bath temperature and electric current density for the electrodeposition operation, pits, cracks or crevices of the desired size, depth and interspace can be obtained.
  • a thin chromium plating layer may be formed on the metal surface by electrodeposition at an optimum electric current density, described previously for the formation of a glossy chromium plating, prior to the chromium plating operation in the first invention.
  • the formation of such thin chromium plating layer is advantageous, though not essential, in producing an improved binding between the metal surface and the chromium plating layer having the projections, which will subsequently be formed on said metal surface.
  • the metal plate used in the method of the third invention must also be subjected to pre-treatments, such as treatments for the purging of oxide film, removal of fat and purging of rust, before the chromium plating electrodeposition operation, as well as in the case of ordinary plating operation.
  • FIGS. 1 to 10 inclusive are cross sectional views diagrammatically showing various states of chromium platings formed on a metal surface by the methods of the present invention
  • FIGS. 3' to 7 inclusive are fragmentary cross sectional views diagrammatically showing in enlargement the states of the respective chromium platings shown in FIGS. 3 to 7;
  • FIGS. 9' and 10 are fragmentary cross sectional views diagrammatically showing in enlargement of the respective chromium platings shown in FIGS. 9 and ll).
  • FIGS. 1 to and FIGS. 3 to 5' inclusive are views diagrammatically showing the cross sections of a metal substrate and a plating layer formed thereon.
  • FIGS. 1 and 2 are the case wherein the metal surface is not previously roughened.
  • FIG. 1 is a view of a metal substrate 1 with a chromium plating layer 2 formed thereon
  • FIG. 2 is a view of the chromium plating layer 2 on the metal substrate 1 after pits, cracks or crevices 3 formed therein by electrolytic etching.
  • FIGS. 3 to 5 inclusive show the case wherein the chromium plating layer is formed on a roughened metal surface and FIGS. 3' to 5 are enlarged view of the chromium plating layers shown in FIGS.
  • FIGS. 3 and 3 are views of the metal substrate 1 whose surface 4 has previously been roughened by mechanical or chemical means
  • FIGS. 4 and 4 are views of the metal substrate 1 with a chromium plating lever 2 formed on the roughened surface 4 thereof.
  • the chromium plating layer 2 has a cross section as shown in FIGS. 5 and 5, with pits, cracks or crevices 3 formed therein.
  • the cross section of the metal substrate and the chromium plating layer which is obtained by plating the roughened surface of a metal substrate with chromium and electrolytically etching the chromium plating thus formed, is more complicated than that shown in FIG.
  • the surface of the metal having the cross section shown in FIG. 2 or FIG. 5, which is obtained in the manner described, is suitable for being coated wtih a fluorine-containing polymer.
  • a fluorine-containing polymer According to the second invention, such surface is further coated with the aforesaid chromium plating and the resultant layer of chromium plating is etched electrolytically by reversing the polarities of electrodes, whereby finer and more complicate pits, cracks or crevices are provided on the surface of the metal and accodingly the binding strength between the metal and the fluorine-containing polymer coating formed thereon is further improved.
  • the second chromium plating operation may be carried out in the same manner as the first chromium plating operation but where the pits, cracks or crevices to be produced by the following electrolytic etching are desired to be finer than those produced by the first electrolytic etching operation, the bath temperature for the second plating operation is preferably at C. lower than the bath temperature for the first plating operation.
  • the operation for the formation of the second chromium plating layer (indicated at 5 in FIG. 6) must be stopped before the pits, cracks or crevices 3 in the first chromium plating layer 2 are filled with said second chromium plating layer. Upon completion of this, the polarities of the electrodes are reversed, whereby finer pits, cracks or crevices (indicated at 6 in FIG. 7') are formed.
  • FIGS. 6 and 7 and FIGS. 6' and 7' are views diagrammatically showing the cross sections of the metal and chromium plating, which are obtained in different stages of treating the surface of the chromium plating layer shown in FIG. 2 in the manner described above.
  • reference numeral 5 designates the chromium plating layer newly formed and 6 designates the fine pits, cracks or crevices formed therein as a result of electrolytic etching. The same treatment may be made on the surface of the chromium plating layer shown in FIG. 5 to obtain a further complicated surface.
  • the formation of the double layers of chromium plating on the metal surface as described above is advantageous not only in that the binding strength therebetween can be improved as described previously but also in that the electrodeposition velocity of the first chromium plating layer can be made higher than in the case of a single layer.
  • This is because of the following reason. Namely, when an excessively high electro-deposition velocity is used for the formation of a single chromium plating layer on a metal surface, only a small binding strength is obtained between the metal surface and a fluorine-containing polymer film provided on said metal surface after the electrolytic etching of said chromium plating layer and for this reason the electrodeposition velocity must be maintained below a predetermined value by controlling the bath temperature and the electric current density used. Such restriction is not imposed on the operation of forming the double layers of chromium plating.
  • the surface of the chromium plating thus formed no longer has the gloss inherent to metallic chromium and appears gray in most cases, and a variety of fluorine-containing polymer coatings can be formed directly thereon.
  • the methods of the first and second inventions can be .operated with any type of fluorine-containing polymer but are most advantageously used with such fluorine-containing polymer in particular which are poorly adhesive to other substances.
  • any conventional method can be employed but by employing the methods of the present inventions there is brought about the advantage that the coating operation can be simplified because the methods of the present inventions do not necessarily involve the step of applying a primer on the metal surface which has heretofore been required before coating such fluorine'containing polymer in particular as polyethylene tetrafiuoride and polyethylene chlorotrifiuon'de in the form of dispersion or enamel, for improving the binding property of said polymer.
  • FIGS. 8 to 10 and FIGS. 9 t 10' inclusive The cross sections of a metal and a plating layer formed thereon in various stages of the operation according to this method are diagrammatically shown in FIGS. 8 to 10 and FIGS. 9 t 10' inclusive.
  • FIGS. 9' and 10' are fragmentary enlarged view of FIGS. 9 and 10 respectively.
  • FIG. 8 shows a metal substrate 1 with a thin chromium plating layer 2 formed on the surface thereof at an optimum bath temperature and optimum current density. When the current density is raised successively after the formation of the thin chromium plating layer, projections are formed on said plating layer as shown in FGIS. 9 and 9.
  • FIGS. 8 shows a metal substrate 1 with a thin chromium plating layer 2 formed on the surface thereof at an optimum bath temperature and optimum current density. When the current density is raised successively after the formation of the thin chromium plating layer, projections are formed on said plating layer as shown in FGIS. 9 and 9.
  • FIGS. 10 and 10' show the condition of the chromium plating surface which has been subjected to electrolytic etching effected by reversing the polarities of electrodes after formation of the projections shown in FIG. 9. Namely, FIGS. 10 and 10 show pits, cracks or crevices 4 formed in the projections 3.
  • the surface of the chromium plating thus formed is gray or grayish white in color.
  • fluorine-containing polymer coating is formed on the surface of the chromium lating, the fluorine-containing polymer fills the interspaces between the projections 3, and pits, cracks or crevices 4 to produce the so-called anchor effect, and as a result a binding effect is obtained which is unexpectedly remarkable as compared with that obtainable by treating the metal surface mechanically or chemically.
  • the method of this invention is extremely effective for coating a metal surface with the aforementioned fluorine-containing polymer, such as polyethylene tetrafluoride, polyethylene chlorotrifluoride and ethylene tetrafluoride-propylene hexafiuoride copolymer, which are poor in binding property.
  • fluorine-containing polymer such as polyethylene tetrafluoride, polyethylene chlorotrifluoride and ethylene tetrafluoride-propylene hexafiuoride copolymer, which are poor in binding property.
  • any conventional method can be employed but by employing the method of this invention there is brought about the advantage that the coating operation can be simplified because the method of the invention does not necessarily involve the step of applying a primer on the metal surface which has heretofore been required before coating such polymer in particular as polyethylene tetrafluoride and polyethylene chlorotrifiuoride in the form of dispersion or enamel, for improving the binding property of said polymer.
  • Example 1 and 3 exemplify the method of the first invention
  • Example 2 exemplifies the method of the second invention
  • Example 4 exemplifies the method of the third invention.
  • EXAMPLE 1 The surface of a soft steel plate was treated, before forming a chromium plating thereon, in the following manner for the purging of an oxide film and removal of stain and fat. Namely, the surface of the soft steel plate was l) polished with Alundum, lapping powder No. 600, and then with lapping powder No. 100, (2) washed with water, (3) subjected to electrolytic degreasing at 80 C. in an electrolyte containing 50 g./l. of sodium carbonate and 50 g./l.
  • the surface of soft steel plate thus treated was plated with chromium in a chromium plating bath consisting of 250 g./l. of chromic anhydride and 2.5 g./l. of sulfuric acid for 3 hours at a bath temperature of 50 C. and a current density of 50 a./dm. whereby a glossy chromium plating was formed on said surface.
  • a chromium plating bath consisting of 250 g./l. of chromic anhydride and 2.5 g./l. of sulfuric acid for 3 hours at a bath temperature of 50 C. and a current density of 50 a./dm.
  • a dispersion containing 60% by weight of polyethylene tetrafluoride was sprayed on the surface of the chromium plating layer thus formed, dried under an infrared lamp and sintered at about 380 C. This operation was repeeated 10 times and thereby a polyethylene tetrafluoride film of about 0.2 mm. in thickness was formed on the chromium plating layer.
  • the chromium plating operation was carried out for 2 hours at a bath temperature of C. and a current density of 60 a./dm. Then, the chromium plating thus formed was subjected to electrolytic etching for 8 minutes under the same conditions by reversing the polarities of electrodes, and thereafter the surface of the chromium plating layer was further plated with chromium for 2 hours in the same plating bath at 40 C. at a current density of 25 a./dm.
  • the chromium plating surface thus obtained was then coated with a polyethylene tetrafluoride film in the same manner as in Example 1 and the binding strength of said film was measured in the same manner as in Example 1. As a result, it was found that the binding strength was 2.6 kg./cm. or higher. A binding strength higher than 3.0 lg./cm. could not be measured because the specimen was cut at a point where the binding strength between the film and the metal showed said value.
  • EXAMPLE 3 The surface of a soft steel plate was roughened by the sand blast method in such a manner that the average height of the projections formed is about 25 After subjecting the roughened surface to the pre-treatment which follows the electrolytic degreasing in Example 1, a chromium plating was formed thereon for 3 hours in a chromium plating bath of the same composition as in Example 1 at a temperature of 40 C. and a current density of 25 a./dm. Thereafter, the resultant chromium plating layer was electrolytically etched for 15 minutes under the same conditions by reversing the polarities of electrodes. The plating surface thus obtained was gray in color and a microscopic observation revealed that pits, cracks or crevices having depths of 8 to 28p. had been formed in said plating layer.
  • a polyethylene tetrafluoride film was coated on the chromium plating surface in the same manner as in Example 1 and the binding strength was measured in the same manner as in Example 1. It was found that the binding strength was 2.5 kg./cm. or higher. The specimen was cut at a point where the binding strength between the film and the metal was 3.0 kg./ cm.
  • EXAMPLE 4 Using a plating bath of the same composition as in Example 1, a soft steel plate which had previously been subjected to the same pre-treatments as in Example 1 was subjected to electrolytic etching for 2 seconds in said bath by reversing the polarities of electrodes. Then, the etched surface was further plated with chromium in the same bath at a temperature of 35 C. and a current density of a./dm. for minutes. Successively thereafter, the chromium plating Was continued for 2 hours at a current density of 40 a./dm. and a light gray plating surface was obtained.
  • a section of the chromium plating layer was observed through a microscope and it was found that a number of substantially semispherical projections had been formed on the surface of said plating layer, whose heights were not greater than about 42 Then, the plating surface was electrolytically etched for 8 minutes under the same conditions by reversing the polarities of electrodes and a grayish white surface was obtained. Through a microscope, it was found that a number of pits, cracks or crevices had been formed in the projections, whose depths were from 3 to The surface of the chromium plating layer thus formed was coated with a polyethylene tetrafluoride film in the same manner as in Example 1.
  • the present invention is particularly advantageously used for the application of fluorine-containing polymer to the surfaces of various rollers, bearings, spinning machine parts, pistons and cylinders in pneumatic and hydraulic machinery.
  • polyethylene tetrafluoride is applied, for example, on the surface of a bearing, etc.
  • the frictional resistance of the surface thereof can be prevented from becoming excessiveely large even when the polyethylene tetrafluoride film had been worn out to some extent, owing to the lubrcity of the polyethylene tetrafluoride present in the pits, cracks or crevices in the chromium plated layer and the hard surface of said chromium plated layer.
  • the releasing property of the metal surface with respect to other articles can be maintained highly satisfactorily.
  • the coating methods according to the present invention it is possible to obtain a binding property and wear resisting property or lubricating property which are far more superior to those of the conventional coated films, depending upon the pupose of use of the coated film. Further, the methods of the present invention can be used in a wide range of application.
  • a method of coating a metal surface with a fluorinecontaining polymer comprising electrolytically forming a frosted chromium plated layer on the metal surface whereby projections are formed on the surface of said chromium plated layer, electrolytically etching the surface of'said chromium plated layer by reversing polarities of the electrodes to form a number of pits, cracks or crevices in said surface, coating a dispersion of fluorinecontaining polymer on the resultant surface and sintering said polymer to form a continuous film of said polymer on said surface, thereby anchoring said film to said surface by portions of said polymer filling said pits, cracks or crevices.
  • a method of coating a metal surface with a fluorinecontaining polymer comprising electrolytically forming a first chromium plated layer on the metal surface, electrolytically etching the surface of said chromium plated layer by reversing the polarities of the electrodes to form a number of pits, cracks or crevices therein, superposing a second chromium plated layer over said first chromium plated at a bath temperature lower than the bath temperature for forming the first chromium plated layer, electrolytically etching the surface of the second chromium layer by reversing the polarities of the electrodes to form a number of further pits, cracks or crevices therein, coating a dispesion of a fluorine-containing polymer on the resultant surface and sintering said polymer to form a continuous film of said polymer on said surface, thereby anchoring said film to said surface by portions of said polymer filling said pits, cracks or crevices

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  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electroplating And Plating Baths Therefor (AREA)
  • Electroplating Methods And Accessories (AREA)
  • Laminated Bodies (AREA)
US726350A 1968-05-07 1968-05-03 Method of coating metal surfaces with a fluorine-containing polymer Expired - Lifetime US3591468A (en)

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DE (1) DE1771323B2 (enrdf_load_stackoverflow)
GB (1) GB1228853A (enrdf_load_stackoverflow)

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3945893A (en) * 1972-12-30 1976-03-23 Suzuki Motor Company Limited Process for forming low-abrasion surface layers on metal objects
US4094749A (en) * 1976-07-06 1978-06-13 Tools For Bending, Inc. Surface treatment with durable low-friction material
US4623546A (en) * 1985-04-01 1986-11-18 The Quaker Oats Company Method for manufacturing crisp rice
US4917779A (en) * 1989-05-23 1990-04-17 Usui Kokusai Sangyo Kabushiki Kaisha Process for the formation of fluoroplastic coating on surface of zinc, zinc alloy or zinc plating
US4950563A (en) * 1988-12-27 1990-08-21 International Fuel Cells Phosphoric acid fuel cells with improved corrosion resistance
US5021259A (en) * 1988-08-29 1991-06-04 International Fuel Cells Corp. Method of applying a continuous thermoplastic coating with one coating step
EP0434757A4 (en) * 1988-09-19 1992-05-13 Rexham Corporation Improved fluoropolymer-metal laminates
US5296183A (en) * 1992-08-21 1994-03-22 Dow-United Technologies Composite Products, Inc. Method for comolding property enhancing coatings to composite articles
US6320129B1 (en) * 1999-09-21 2001-11-20 Industrial Technology Research Institute Method for making electrode of polymer composite
US6666449B2 (en) * 2001-05-15 2003-12-23 Defosse Stephen Francis Star wheel surface enhancement and process of manufacture
US20050072682A1 (en) * 2003-10-07 2005-04-07 Kenneth Lore Process and apparatus for coating components of a shopping cart and a product
US20120032566A1 (en) * 2010-08-03 2012-02-09 Hon Hai Precision Industry Co., Ltd. Housing and fabrication method thereof
US20130154192A1 (en) * 2011-12-15 2013-06-20 Trelleborg Sealing Solutions Us, Inc. Sealing assembly
US11499116B2 (en) 2019-12-17 2022-11-15 Raytheon Technologies Corporation Friction reducing polyelectrolyte coating

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2752722C2 (de) * 1977-11-25 1982-09-30 Tools for Bending, Inc., Denver, Col. Verfahren zum Überziehen einer Metalloberfläche mit einem Perfluorkohlenwasserstoffharz
US4347277A (en) * 1978-11-03 1982-08-31 General Signal Corporation Corrosion resistant coated articles which include an intermediate coating layer of a thermosetting polymer and non-siliceous filler
US4237177A (en) * 1978-11-03 1980-12-02 General Signal Corporation Corrosion-resistant coated articles
DE3232726A1 (de) * 1982-04-20 1983-10-20 Armourcote Surface Treatments Ltd., Leeds, York Verfahren zur herstellung von mehrschichtigen oberflaechen
DE19840966A1 (de) * 1998-09-08 2000-03-09 Impreglon International L L C Oberflächenbeschichtung für ein Substrat und Verfahren zur Ausbildung einer Oberflächenbeschichtung
DE102004027717A1 (de) * 2004-06-07 2005-12-22 Accuride International Gmbh Beschichtete Teleskopschiene
JP5878294B2 (ja) * 2011-01-11 2016-03-08 地方独立行政法人東京都立産業技術研究センター チタン部材の曲げ加工方法および曲げ加工具

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3945893A (en) * 1972-12-30 1976-03-23 Suzuki Motor Company Limited Process for forming low-abrasion surface layers on metal objects
US4094749A (en) * 1976-07-06 1978-06-13 Tools For Bending, Inc. Surface treatment with durable low-friction material
US4623546A (en) * 1985-04-01 1986-11-18 The Quaker Oats Company Method for manufacturing crisp rice
US5021259A (en) * 1988-08-29 1991-06-04 International Fuel Cells Corp. Method of applying a continuous thermoplastic coating with one coating step
EP0434757A4 (en) * 1988-09-19 1992-05-13 Rexham Corporation Improved fluoropolymer-metal laminates
US4950563A (en) * 1988-12-27 1990-08-21 International Fuel Cells Phosphoric acid fuel cells with improved corrosion resistance
US4917779A (en) * 1989-05-23 1990-04-17 Usui Kokusai Sangyo Kabushiki Kaisha Process for the formation of fluoroplastic coating on surface of zinc, zinc alloy or zinc plating
US5296183A (en) * 1992-08-21 1994-03-22 Dow-United Technologies Composite Products, Inc. Method for comolding property enhancing coatings to composite articles
US6320129B1 (en) * 1999-09-21 2001-11-20 Industrial Technology Research Institute Method for making electrode of polymer composite
US6666449B2 (en) * 2001-05-15 2003-12-23 Defosse Stephen Francis Star wheel surface enhancement and process of manufacture
US20050072682A1 (en) * 2003-10-07 2005-04-07 Kenneth Lore Process and apparatus for coating components of a shopping cart and a product
US20120032566A1 (en) * 2010-08-03 2012-02-09 Hon Hai Precision Industry Co., Ltd. Housing and fabrication method thereof
US20130154192A1 (en) * 2011-12-15 2013-06-20 Trelleborg Sealing Solutions Us, Inc. Sealing assembly
US11499116B2 (en) 2019-12-17 2022-11-15 Raytheon Technologies Corporation Friction reducing polyelectrolyte coating

Also Published As

Publication number Publication date
DE1771323A1 (de) 1972-02-03
GB1228853A (enrdf_load_stackoverflow) 1971-04-21
DE1771323B2 (de) 1974-03-14

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