EP0127620B1 - Cosedimentation electrolytique de zinc et de graphite, ainsi que le produit resultant - Google Patents
Cosedimentation electrolytique de zinc et de graphite, ainsi que le produit resultant Download PDFInfo
- Publication number
- EP0127620B1 EP0127620B1 EP19830900525 EP83900525A EP0127620B1 EP 0127620 B1 EP0127620 B1 EP 0127620B1 EP 19830900525 EP19830900525 EP 19830900525 EP 83900525 A EP83900525 A EP 83900525A EP 0127620 B1 EP0127620 B1 EP 0127620B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- zinc
- graphite
- electrolyte
- codeposit
- plating
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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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
- C23C22/24—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 hexavalent chromium compounds
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D15/00—Electrolytic or electrophoretic production of coatings containing embedded materials, e.g. particles, whiskers, wires
- C25D15/02—Combined electrolytic and electrophoretic processes with charged materials
-
- 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
Definitions
- Automotive metal fasteners are usually coated or plated to enhance various characteristics such as resistance to corrosion, resistance to seizing/galling, low fastening friction, economy, solderability, and resistance to the stick-slip phenomenon (which is a repeated sticking followed by repeated slipping during fastener tightening operations).
- cadmium has been employed to impart lubricity and good sacrificial corrosion protection, particularly in a marine environment (see Modern Electroplating, by F. A. Lowenheim, published by John Wiley & Sons, 3rd Edition, p. 663, 1974).
- cadmium is subject to two disadvantages: (a) it has a toxic effect during processing, and (b) it is significantly expensive.
- codeposited particles can be considered nonconductive and normally would not respond to the normal electrolytic action, but it was found that even graphite would plate or codeposit under very strained and undesirable conditions with nickel.
- the metal matrix and codeposited particles were viewed as to their antifriction, antiseizing, and dry lubrication properties and found them not lower than zinc or cadmium. No investigation was made of the mode of corrosion of such codeposits. Without exploring proper processing parameters, the author concluded that codeposition was feasible only at conventional metal plating parameters. Similar observations were made by Parker as to electroless nickel deposits, entitled “Hardness and Wear Resistance Tests of Electroless Nickel Deposits", Journal of Plating, Vol. 61, p. 834, September 1974.
- DE-A-2325559 discloses a coating of Zn and graphite. Zn and graphite are simultaneously electrodeposited.
- a method of electrodepositing zinc and graphite onto conductive metal substrate by the use of an electrolytic cell having a zinc anode and the metal substrate connected as a cathode comprising the steps of immersing said substrate in a cleansed condition into an acid/zinc plating electrolyte containing at least 40 g/I zinc ions and 30-110 g/I insoluble bulk graphite, said electrolyte having a pH of 5-5.7 and energizing said electrolytic cell at a sufficient current density to plate out zinc onto said surface without burning while continuously agitating said graphite into uniform suspension throughout said electrolyte, said agitation being periodically interrupted to allow said graphite to settle and comingle with said zinc as it is plating out on said cathode, the codeposit of zinc and graphite on said substrate containing uniformly distributed graphite in an amount of 30-48% by weight of the codeposit, a coefficient of friction equal to or less than .130, at a plated thickness of
- the codeposit may be subject to an additional step of dipping into a chromate passivation solution for a period of 10-30 seconds in order to form a conversion zinc chromate coating on the outer layer of said codeposit.
- the layer of zinc chromate has a thickness of .00005 cms (.00002") so that optimally the coated combination will exhibit consistent torque performance at a torque load of 40 pounds, a coefficient of friction of about .112 or less, and no red rust in a salt spray environment for at least 120 hours.
- the fastener When the codeposited coating is applied to a threaded fastener, the fastener will preferably exhibit a consistent torque tension relationship during tightening and have good solderability characteristics using either a resin solder cord or a zinc chloride containing flux.
- the conductive metal substrate is a metallic threaded fastener which may be comprised of steel, copper, nickel, brass, bronze, zinc and aluminum.
- the agitation is preferably interrupted for 15-60 seconds at intervals of 15-80 seconds. It is advantageous if the particle size of the graphite employed is of an extremely fine character, and preferably is of a colloidal nature having a particle size of 1-25 microns.
- the electrolyte is of the acid chloride type, created by either mixing 70-85 g/I zinc chloride with 100150gII of potassium chloride, or 45-110 g/l of zinc chloride when dissolved with 100-200 g/I of sodium chloride.
- the acid chloride bath contains also boric acid in an amount of 26 ⁇ 40 g/I.
- the electrolyte may be improved by incorporating a grain refiner in the form of gelatin in an amount of .41 g/I of electrolyte, and a cationic surfactant in the form of cocamine acetate in an amount of .1-.4 g/I of electrolyte.
- the cleaning of the substrate may include immersion in a caustic cleansing solution to remove oils and other organic materials followed by a clean water rinse, and then immersion in a pickling solution to remove any oxides thereon, again followed by water rinse.
- a barrel plating process whereby the apparatus is comprised of a mechanically rotated barrel which is perforated and contains a metallic plate bolted to the bottom of the barrel which in turn is connected to a commutator ring on the outside of the barrel.
- the barrels are made of inert material such as polypropylene.
- the cathode contact with the fasteners is usually made by metal discs on the bottom of the cylinder. The electrolyte permeates the barrel through the perforations and the anode is suspended just below the level of the solution.
- This invention has discovered that a codeposit of zinc and graphite with a critically high content of graphite will provide an unusually good combination of physical characteristics, including an ultralow coefficient of friction.
- the physical characteristics may comprise anticorrosion properties, good solderability, economy of processing and little or no stick slip problem.
- the codeposit of zinc and graphite has particular utility in the coating of fasteners, pins and gears.
- a preferred method mode for obtaining the codeposit of this invention is as follows.
- a processing and electrolytic plating system is prepared.
- a barrel plating mode may be employed whereby rotatable cylinders 10, constructed of acid resistant, nonabsorbant material (such as polypropylene, resin bonded fiberglass, hard rubber, PVC, lucite, and phenolic laminates) are used to contain the parts to be plated while being tumbled.
- the cylinders are perforated and are mounted for rotation upon a horizontal axis, the trunions 11 for the axis being supported in a carriage 12 which is moved from tank to tank and is lowered into each tank for treatment therein.
- the series of tanks that may be employed with this method, and barrel plating apparatus include a series of cleaning and rinsing tanks (not shown, which are interposed between process tanks).
- One or more of electrolytic plating tanks 13-14-15 are employed, followed by a suitable rinse tank 16. Only the electrolytic plating tanks are energized and contain an electrolyte.
- the parts, such as metal fasteners, are loaded in a bulk fashion into the cylinder through an access door thereof; the parts are connected as a cathode in the electrolytic plating cell by use of a metal plate bolted to the bottom of the barrel for contact with the batch of parts.
- the plate is connected by slip ring to an outside electrical supply.
- the anode can comprise a plurality of zinc elements extending into the bath containing the electrolyte solution and into which the barrels are lowered.
- the substrate or, in this case, a bulk quantity of metallic fasteners, is loaded into the barrel plating cylinder and carried through a series of cleaning tanks, which may preferably comprise a first bath having a highly alkaline solution effective to remove oil and gum deposits on the metallic substrate.
- the alkaline cleansed metal substrate is then rinsed by use of conventional tap water and then immersed in a pickling solution containing a concentration of about 30% hydrochloric acid, which is effective to remove oxides, followed by a conventional water rinse.
- the parts Prior to immersing the cleansed substrate into an acid zinc plating electrolyte for depositing a codeposit, the parts may preferably be preplated with .0005 cms (0.0002") zinc in a conventional acid zinc plating electrolyte.
- the electrolyte for the codeposit contains 40 g/I zinc ions and 30-110 g/l insoluble bulk graphite.
- the zinc ions are obtained in the electrolyte by introducing a zinc anode into the bath solution; the bulk graphite is preferably introduced in a fine grade condition, optimally colloidal graphite, having a particle size in the range of 1-25 microns. Crude foundry grade graphite is operable within the scope of this invention, crude graphite having an average particle size of 25-100 microns. Utilizing the finer colloidal graphite will obtain a much smoother codeposit having typically an average particle size of 2 microns.
- the graphite is added to the electrolyte in amounts less than 30 g/l, a noticeable increase in the coefficient of friction of the codeposit will result and make the coating less effective in performing as a low friction composite. If the graphite is added to the solution and maintained in a suspension quantity of greater than 110 g/I, the graphite will plate out in an amount which will be greater than 50% of the codeposit and thus substantially reduce the ability of the codeposit to have anticorrosion characteristics attributable to the presence of zinc.
- the acid zinc electrolyte is prepared by adding to an aqueous solution 45-110 g/I zinc chloride and 100-200 g/I sodium chloride.
- the pH of such acid bath should be maintained in the range of 5-5.7 and optimally about 5.3. This bath has the advantage of plating on difficult metals and will have an almost 100% cathode efficiency.
- the acid chloride bath may be prepared by using 70-85 g/I zinc chloride and 100-150 g/I of potassium chloride. Boric acid in the range of 26-40 g/I may be added as a buffering agent.
- .4-1 g/I of unflavored gelatin may be added to the electrolyte. Additionally, .1-4.0 g/I cocamine acetate (having the molecular formula of C 12 H 2 ,NH 3 ) is added, which serves to facilitate the deposition of nonconductive particles.
- the pH range should be regulated as given. If higher than such range, zinc hydroxide will form which is undesirably insoluble. If lower than 5, the acidity of the electrolyte will affect cohesion.
- the electrolyte should be maintained in a temperature range of 24-32°C (7590°F).
- the electrolytic cell is energized at a sufficient current density to plate the zinc onto the substrate without burning while continuously agitating the graphite into suspension throughout said electrolyte.
- the agitation is periodically interrupted to allow the graphite to settle and comingle with the zinc as the plating takes place on the cathode.
- the agitation is carried out by the use of air pulsing and is interrupted for periods of 15 ⁇ 60 seconds at intervals of 15-180 seconds. During all other times the air pulsing is on.
- the current density is preferably employed in the low range of 1-20 amps per square foot (.1-2.0 amps/dm 2 ). If the current density is lower than this value, insufficient plating zinc will take place.
- the surface profile of a codeposited material will have a surface roughness which will vary depending upon whether highly conductive particles are entrapped by the metal or whether the particles are substantially nonconductive.
- cobalt particles are enveloped by the primary plating metal causing a relatively rough surface to be formed.
- Graphite particles which carry a low level of electrostatic charge, are embedded within the plating metal primarily by a settling action and are not enveloped by the plating metal resulting in a much smoother finish (see Figure 3).
- the rate of zinc metal deposition affects the entrapment rate of the graphite particles during the coating of the cathode.
- the graphite deposition rate and graphite particle volume can be optimized (see Figure 5). If a current density of between .8 ⁇ 1.6 amps/dm 2 is employed, the best graphite rate as well as graphite volume deposition is obtained. This is conditioned upon the interruption of the agitation force for 15-60 second periods at intervals of 15-180 seconds to allow for such deposition rate to take place.
- the electroplated codeposit in a solution containing an acid chromate for a period of 10 ⁇ 45 seconds to form a very thin chromate outer coating on the metal substrate.
- the chromate should typically have a thickness of 2.54x2- 5 cms (2- S inches) thick.
- the zinc/graphite plated part is dipped in a chromating solution consisting of 30 g/f chromic acid, 10 cc/I phosphoric acid, 5 cc/I hydrochloric acid, 5 cc/I nitric acid, and 5 cc/I sulfuric acid for a period of about 30 seconds, followed by a warm rinse of about 30 seconds.
- the chromate conversion coating on the codeposit of this invention renders exceptionally good corrosion resistance because of (a) the corrosion inhibiting effect of hexavalent chromium contained in the chromate film, and (b) to the physical barrier presented by the chromate film itself.
- the film is formed by the chemical reaction of the hexavalent chromium with the zinc metal surface in the presence of activators in the acid solution.
- the hexavalent chromium is partially reduced to trivalent chromium during the reaction with a concurrent rise in pH, forming a complex mixture consisting largely of hydrated basic chromium chromate and hydrous oxides of both chromium and the zinc metal.
- the activators useful in forming the conversion coating include acetate formate, sulphate, chloride, fluoride, nitrate phosphate, and sulphamate ions.
- the immersion time for a conversion coating herein is relatively short, a period of 20-30 seconds.
- a series of samples were prepared in conformity with the preferred mode. Each of the samples were iron based nuts; some preplated with 5 microns zinc, and all plated with 8 microns of zinc/graphite.
- the zinc/graphite plating solution contained 75 g/I of graphite.
- the zinc/graphite codeposit in some samples was passivated with a chromate film of a thickness of 0.00005 cms (0.00002").
- the samples were subjected to a chemical content analysis to determine the content of graphite and the corresponding coefficient of friction at a torque load of 40 ft/lbs.
- the solution was varied with a variety of graphite contents; the results of such analysis are shown in the following Table 1.
- the codeposit of this invention is dry to the touch, which is often commercially difficult to consistently achieve with fasteners coated with phosphate and oil.
- the shelf life of the codeposit is excellent, having a life of well over one year, and is economical to finish while presenting no hazards with respect to toxic processing considerations.
- the raw materials for the system are relatively plentiful.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Mechanical Engineering (AREA)
- Electroplating Methods And Accessories (AREA)
Abstract
Claims (13)
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/US1982/001689 WO1984002149A1 (fr) | 1982-12-01 | 1982-12-01 | Cosedimentation electrolytique de zinc et de graphite, ainsi que le produit resultant |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0127620A1 EP0127620A1 (fr) | 1984-12-12 |
EP0127620A4 EP0127620A4 (fr) | 1985-07-01 |
EP0127620B1 true EP0127620B1 (fr) | 1987-09-23 |
Family
ID=22168421
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19830900525 Expired EP0127620B1 (fr) | 1982-12-01 | 1982-12-01 | Cosedimentation electrolytique de zinc et de graphite, ainsi que le produit resultant |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP0127620B1 (fr) |
JP (1) | JPS59502108A (fr) |
BR (1) | BR8208101A (fr) |
DE (1) | DE3277378D1 (fr) |
WO (1) | WO1984002149A1 (fr) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB8818069D0 (en) * | 1988-07-29 | 1988-09-28 | Baj Ltd | Improvements relating to electrodeposited coatings |
US20110305919A1 (en) | 2010-06-10 | 2011-12-15 | Authentix, Inc. | Metallic materials with embedded luminescent particles |
CN114597482B (zh) * | 2022-03-14 | 2023-04-28 | 浙江大学温州研究院 | 一种用于锌电池负极的固态电解质界面的原位制备方法 |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3061525A (en) * | 1959-06-22 | 1962-10-30 | Platecraft Of America Inc | Method for electroforming and coating |
FR1579266A (fr) * | 1967-09-09 | 1969-08-22 | ||
DE2325559A1 (de) * | 1973-05-19 | 1974-11-28 | Dietmar Loeffler | Verfahren zur galvanischen herstellung von graphit enthaltenden metallueberzuegen |
JPS533446B2 (fr) * | 1973-11-01 | 1978-02-07 | ||
US3922208A (en) * | 1973-11-05 | 1975-11-25 | Ford Motor Co | Method of improving the surface finish of as-plated elnisil coatings |
JPS51143534A (en) * | 1975-06-05 | 1976-12-09 | Kawasaki Steel Co | Steel plate coated with aluminummdispersed zinc by composite plating |
JPS5224941A (en) * | 1975-08-21 | 1977-02-24 | Kawasaki Steel Co | Surface treated steel plate for molding and its production method |
-
1982
- 1982-12-01 WO PCT/US1982/001689 patent/WO1984002149A1/fr active IP Right Grant
- 1982-12-01 JP JP83500658A patent/JPS59502108A/ja active Pending
- 1982-12-01 BR BR8208101A patent/BR8208101A/pt unknown
- 1982-12-01 DE DE8383900525T patent/DE3277378D1/de not_active Expired
- 1982-12-01 EP EP19830900525 patent/EP0127620B1/fr not_active Expired
Also Published As
Publication number | Publication date |
---|---|
EP0127620A4 (fr) | 1985-07-01 |
BR8208101A (pt) | 1984-10-02 |
JPS59502108A (ja) | 1984-12-20 |
EP0127620A1 (fr) | 1984-12-12 |
WO1984002149A1 (fr) | 1984-06-07 |
DE3277378D1 (en) | 1987-10-29 |
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