GB2141138A - Trivalent chromium electroplating electrolytes and rejuvenation thereof - Google Patents

Trivalent chromium electroplating electrolytes and rejuvenation thereof Download PDF

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GB2141138A
GB2141138A GB08412122A GB8412122A GB2141138A GB 2141138 A GB2141138 A GB 2141138A GB 08412122 A GB08412122 A GB 08412122A GB 8412122 A GB8412122 A GB 8412122A GB 2141138 A GB2141138 A GB 2141138A
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present
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ions
electrolyte
chromium
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Thaddeus Walter Tomaszewski
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OMI International Corp
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OMI International Corp
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Priority claimed from US06/492,304 external-priority patent/US4439285A/en
Priority claimed from US06/492,302 external-priority patent/US4477315A/en
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    • CCHEMISTRY; METALLURGY
    • C25ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25DPROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00Electroplating: Baths therefor
    • C25D3/02Electroplating: Baths therefor from solutions
    • C25D3/04Electroplating: Baths therefor from solutions of chromium
    • C25D3/06Electroplating: Baths therefor from solutions of chromium from solutions of trivalent chromium
    • CCHEMISTRY; METALLURGY
    • C25ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25DPROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D21/00Processes for servicing or operating cells for electrolytic coating
    • C25D21/16Regeneration of process solutions
    • C25D21/18Regeneration of process solutions of electrolytes

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  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electroplating And Plating Baths Therefor (AREA)

Abstract

An aqueous acidic trivalent chromium electrolyte comprises an electrolyte containing trivalent chromium ions, a complexing agent, halide ions, ammonium ions and an additive agent comprising a metal ion selected from neodymium, gold, silver, platinum, palladium, rhodium, iridium, osmium, ruthenium, rhenium, gallium, germanium, indium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, praseodymium, scandium, yttrium, lanthanum, titanium, hafnium, arsenic, selenium, tellurium, cerium, uranium, and mixtures thereof, present in an amount sufficient to reduce the concentration of hexavalent chromium ions formed in the bath at a level at which satisfactory chromium electrodeposits are obtained. An aqueous acidic trivalent chromium electrolyte which has been impaired in effectiveness due to contamination by hexavalent chromium is rejuvenated by adding a metal ion additive agent selected from those listed above.

Description

SPECIFICATION Trivalent chromium electrolyte and process Chromium electroplating baths are in widespread commercial use for applying protective and decorative platings to metal substrates. For the most part, commercial chromium plating solutions heretofore used employ hexavalent chromium derived from compounds.such-s chromic acid) for exanrsple, as the source of the chromium constituent. Such hexavalent chromium electroplating solutions have long been characterized as having limited covering power and excessive gassing particularly around apertures in the parts being plated, which can result in incomplete coverage. Such hexavalent chromium plating solutions are also quite sensitive to current interruptions resulting in so-called "whitewashing" of the deposit.
Because of these and other problems including the relative toxicity of hexavalent chromium, and associated waste disposal problems, extensive work has been conducted in recent years to develop chromium electrolytes incorporating trivalent chromium providing numerous benefits over the hexavalent chromium electrolytes heretofore known. According to the present invention a novel trivalent chromium electrolyte and process for depositing chromium platings has been discovered by which bright chromium deposits are produced having a colour equivalent to that obtained from hexavalent chromium baths.The electrolyte and process of the present invention further provides electroplating employing current densities which vary over a wide range without producing the burning associated with deposits plated from hexavalent chromium plating baths; in which the electrolyte composition minimizes or eliminates the evolution of mist or noxious odours during the plating process; the electrolyte and process provides for excellent coverage of the substrate and good throwing power; current interruptions during the electroplating cycle do not adversely affect the chromium deposit enabling parts to be withdrawn from the electrolyte, inspected, and thereafter returned to the bath for continuation of the electroplating cycle; the electrolyte employs low concentrations of chromium thereby reducing the loss of chromium due to drag-out; and waste disposal of the chromium is facilitated in that the trivalent chromium can readily be precipitated from the waste solutions by the addition of alkaline substances to raise the pH to about 8 or above.
The electrolyte of the present invention further incorporates one or more agents to prevent the formation of detrimental concentrations of hexavalent chromium during bath operation which heretofore has interfered with the efficient electrodeposition of chromium from trivalent chromium plating baths including the reduction in the efficiency and covering power of the bath. In some instances, the buildup of detrimental hexavalent chromium has occurred to the extent that a cessation in electrodeposition of chromium has occurred necessitating a dumping and replacement of the electrolyte.It has also been found that the addition of one or more of the additive agents according to the electrolyte herein disclosed effects a rejuvenation of an electrolyte contaminated with excessive hexavalent chromium restoring the plating efficiency and throwing power of such a bath and avoiding the costly and time consuming step of dumping and replacing the electrolyte.
The benefits and advantages of the present invention in accordance with the composition aspects thereof are achieved by an aqueous acidic electrolyte containing as its essential constituents, controlled amounts of trivalent chromium, a complexing agent present in an amount sufficient to form a chromium complex, halide ions, ammonium ions and an additive agent comprising metal ions selected from the group consisting of neodymium, gold, silver, platinum, palladium, rhodium, iridium, osmium, ruthenium, rhenium, callium, germanium, indium, samarium, europium, gadolinium, terbium, dysporosium, holmium, erbium, thulium, ytterbium, lutetium, praseodymium, scandium, yttrium, lanthanum, titanium, hafnium, arsenic, selenium, tellurium, cerium, uranium, and mixtures thereof, present in an amount effective to maintain the concentration of hexavalent chromium ions at a level below that at which continued optimum efficiency and throwing power of the electroplating bath is maintained. More particularly, the electrolyte can broadly contain about 0.2 to about 0.8 molar trivalent chromium ions, a formate and/or acetate complexing agent present in an amount in relationship to the concentration of the chromium constituent and typically present in a molar ratio of complexing agent to chromium ions of about 1:1 to about 3: 1, a bath soluble and compatible salt or mixture of salts of the additive metal ions present in a concentration of at least about 0.001 gram per liter (g/l) up to about 30 g/l as an agent to reduce the amount of any hexavalent chromium formed during the electroplating process, ammonium ions as a secondary complexing agent present in a molar ratio of ammonium to chromium of about 2.0:1 to about 11:1, halide ions, preferably chloride and bromide ions present in a molar ratio of halide to chromium ions of about 0.8:1 to about 10:1; one or a combination of bath soluble salts to increase bath conductivity comprising compatible simple salts of strong acids such as hydrochloric or sulfuric acid and alkaline earth, alkali and ammonium salts thereof of which sodium fluoroborate comprises a preferred conductivity salt, and hydrogen ions present to provide an acidic electrolyte having a pH of about 2.5 up to about 5.5.
The electrolyte may optionally, but preferably, also contain a buffering agent such as boric acid typically present in a concentration of about 1 molar, a wetting agent present in small but effective amounts of the types conventionally employed in chromium or nickel plating baths as well as controlled effective amounts of anti-foaming agents. Additionally, the bath may incorporate other dissolved metals as an optional constituent including iron, cobalt, nickel, manganese, tungsten or the like in such instances in which a chromium alloy deposit is desired.
According to a preferred aspect of the invention, the additive agent in the above electrolyte comprises one or more metal ions selected from scandium, titanium, yttrium, lanthanium and hafnium.
According to a second preferred aspect, the additive agent comprises one or more metal ions selected from ruthenium, rhenium, palladium, silver, rhodium, osmium, iridium, platinum and gold.
According to a third preferred aspect, the additive agent comprises one or more metal ions selected from gallium, germanium, arsenic, selenium, indium and tellurium.
According to a fourth preferred aspect, the additive agent comprises one or more lanthanide metal ions.
According to a fifth preferred aspect, the additive agent comprises uranium ions.
In accordance with the process aspects of the present invention, the electrodepositin of chromium on a conductive substrate is performed employing the electrolyte at a temperature ranging from about 1 5, to about 45"C. The substrate is cathodically charged and the chromium is deposited at current densities ranging from about 50 to about 250 amperes per square foot (ASF) (5.5 to 27.5 amperes per square decimetre (ASD)) usually employing insoluble anodes such as carbon, platinized titanium or platinum. The substrate, prior to chromium plating, is subjected to conventional pretreatments and preferably is provided with a nickel plate over which the chromium deposit is applied.
In accordance with a further process aspect of the present invention, electrolytes of the trivalent chromium type which have been rendered inoperative or inefficient due to the accumulation of hexavalent chromium ions, are rejuvenated by the addition of controlled effective amounts of the metal ion additive agent to reduce the hexavalent chromium concentration to levels below about 400 parts per million (ppm), and preferably below 50 ppm at which efficient chromium plating can be resumed.
Additional benefits and advantages of the present invention will become apparent upon a reading of the following description of the preferred embodiments and the specific examples provided.
In accordance with the composition aspects of the present invention, the trivalent chromium electrolyte contains, as one of its essential constituents, trivalent chromium ions which may broadly range from about 0.2 to about 0.8 molar, and preferably from about 0.4 to about 0.6 molar. Concentrations of trivalent chromium below about 0.2 molar have been found to provide poor throwing power and poor coverage in some instances whereas, concentrations in excess of about 0.8 molar have in some instances resulted in precipitation of the chromium constituent in the form of complex compounds. For this reason it is preferred to maintain the trivalent chromium ion concentration within a range of about 0.2 to about 0.8 molar, and preferably from about 0.4 to about 0.6 molar.The trivalent chromium iofls can be introduced in the form of any simple aqueous soluble and compatible salt such as chromium chloride hexahydrate, chromium sulphate, and the like. Preferably, the chromium ions are introduced as chromium sulphate for economic considerations.
A second essential constituent of the electrolyte is a complexing agent for complexing the chromium constituent present maintaining it in solution. The complexing agent employed should be sufficiently stable and bound to the chromium ions to permit electrodeposition thereof as well as to allow precipitation of the chromium during waste treatment of the effluents. The complexing agent may comprise formate ions, acetate ions or mixtures of the two of which the formate ions is preferred. The complexing agent can be employed in concentrations ranging from about 0.2 up to about 2.4 molar as a function of the trivalent chromium ions present. The complexing agent is normally employed in a molar ratio of complexing agent tQ chromium ions of from about 1:1 up to about 3:1 with ratios of about 1.5:1 to about 2:1 being preferred.
Excessive amounts of the complexing agent such as formate ions is undesirable since such excesses have been found in some instances to cause precipitation of the chromium constituent as complex compounds.
A third essential constituent of the electrolyte comprises one or a combination of metal ion additive agents in the form of bath soluble and compatible salts present in an amount which varies somewhat depending on the specific metal ion or combination of metal ions employed.
The broadly and specifically preferred concentrations of the specific metal ions are set forth in Table 1.
TABLE 1 CONCENTRATION, g/l METAL ION BROAD PREFERRED Scandium 0.02-20 0.1-1 Yttrium 0.025-20 0.1-1 Lanthanum 0.01-20 0.1-1 Titanium 0.01-20 0.1-1 Hafnium 0.015-15 0.1-1 Arsenic 0.025-10 0.1-1 Selenium 0.025-10 0.1-1 Tellurium 0.025-10 0.1-1 Cerium 0.002-10 0.05-1 Uranium 0.003-10 0.05-1 Gold 0.004-5 0.025-2 Silver 0.003-10 0.025-2- Platinum 0.002-10 0.025-1 Rhodium 0.002-10 0.025-1 Iridium 0.002-10 0.025-1 Osmium 0.001-10 0.02-1 Ruthenium 0.025-10 0.1-1 Rhenium 0.025-10 0.1-1 Gallium 0.060-10 0.1-1 Germanium 0.020-10 0.1-1 Indium 0.030-10 0.05-1 Samarium 0.020-10 0.05-1 Europium 0.020-10 0.05-1 Gadolinium 0.002-10 0.05-1 Terbium 0.002-10 0.05-1 Dysprosium 0.002-10 0.05-1 Holmium 0.002-10 0.05-1 Erbium 0.002-10 0.05-1 Thulium 0.002-10 0.05-1 Ytterbium 0.002-10 0.05-1 Lutetium 0.002-10 0.05-1 Praseodymium 0.002-10 0.05-1 Neodiymium 0.005-17 0.05-5 Palladium 0.002-10 0.025-1 Excess amounts of the metal ion additive agents do appear to adversely effect the operation of the electrolyte in some instances causing dark striations in the plate deposit and a reduction in the plating rate. Typically and preferably, metal ion concentrations are controlled within the preferred ranges set forth in Table 1 which are satisfactory to maintain the hexavalent chromium concentration in the electrolyte below about 400 ppm, preferably below about 100 ppm, and more usually from about 0 up to about 50 ppm at which optimum efficiency of the bath is attained.
The metal ion additive agent is introduced into the electrolyte by any one of a variety of bath soluble and compatible salts including those of only minimal solubility in which event mixtures of such salts are employed to achieve the required concentration.
For example, the neodymium additive agent is introduced into the electrolyte by any one of a variety of neodymium salts which do not adversely effect the chromium deposit and include, for example neodymium trichloride (NdCl3), neodymium acetate [Nd(C2H3O2)3, H20], neodumium bromate [Nd(BrO3)3, 9 H2O], neodymium tribromide (Nd Br3), neodymium trichloride hexahydrate (NdCl3,6H20), and neodymium sulphate octahydrate [Nd2(SO4)3,8H2O], as well as mixtures thereof.
If the trivalent chromium salts, complexing agent, and metal additive salts do not provide adequate bath conductivity by themselves, it is preferred to further incorporate in the electrolyte controlled amounts of conductivity salts which typically comprise salts of alkali metal or alkaline earth metals and strong acids such as hydrochloric acid and sulphuric acid. The inclusion of such conductivity salts is well known in the art and their use minimizes power dissipation during the electroplating operation. Typical conductivity salts include potassium and sodium sulphates and chlorides as well as ammonium chloride and ammonium sulphate.A particularly satisfactory conductivity salt is fluoboric acid and the alkali metal, alkaline earth metal and ammonium bath soluble fluoroborate salts which introduce the fluoroborate ion in the bath and which has been found to further enhance the chromium deposit. Such fluoroborate additives are preferably employed to provide a fluoroborate ion concentration of from about 4 to about 300 g/l. It is also typical to employ the metal salts of sulphamic and methane sulphonic acid as a conductivity salt either alone or in combination with inorganic conductivity salts. Such conductivity salts or mixtures thereof are usually employed in amounts up to about 400 g/l or higher to achieve the requisite electrolyte conductivity and optimum chromium deposition.
It has also been observed that ammonium ions in the electrolyte are beneficial in enhancing the efficiency of the-metal ion additive constituent for converting hexavalent chromium formed to the trivalent state. Particularly satisfactory results are achieved at molar ratios of total ammonium ion to chromium ion ranging from about 2.0:1 up about 11:1, and preferably, from about 3:1 to about 7:1. The ammonium ions can in part be introduced as the ammonium salt of the complexing agent such as ammonium formate, for example, as well as in the form of supplemental conductivity salts.
The effectiveness of the metal ion additive agent in controlling hexavalent chromium formation is also enhanced by the presence of halide ions in the bath of which chloride and bromide ions are preferred. The use of a combination of chloride and bromide ions also inhibits the evolution of chlorine at the anode. While iodine can also be employed as the halide constituent, its relatively higher cost and low solubility render it less desirable than chloride and bromide. Generally, halide concentrations of at least about 1 5 g/l have been found necessary to achieve sustained efficient electrolyte operation. More particularly, the halide concentration is controlled in relationship to the chromium concentration present and is controlled at a molar ratio of about 0.8:1 up to about 10:1 halide to chromium, with a molar ratio of about 2:1 to about 4:1 being preferred.
In addition to the foregoing constituents, the bath may optionally, but preferably also contain a buffering agent in an amount of about 0.1 5 molar up to bath solubility, with amounts typically ranging up to about 1 molar. Preferably the concentration of the buffering agent is controlled from about 0.45 to about 0.75 molar calculated as boric acid. The use of boric acid as well as the alkali metal and ammonium salts thereof as the buffering agent also is effective to introduce borate ions in the electrolyte which have been found to improve the covering power of the electrolyte.In accordance with a preferred practice, the borate ion concentration in the bath is controlled at a level of at least about 1 Og/l. The upper level is not critical and concentrations as high as 60 g/l or higher can be employed without any apparent harmful effect.
The bath further incorporates, as an optional but preferred constituent, a wetting agent or mixture of wetting agents of any of the types conventionally employed in nickel and hexavalent chromium electrolytes. Such wetting agents or surfactants may be anionic or cationic and are selected from those which are compatible with the electrolyte and which do not adversely affect the electrodeposition performance of the chromium constituent. Typically, wetting agents which can be satisfactorily employed include sulphosuccinates or sodium lauryl sulphate and alkyl ether sulphates alone or in combination with other compatible anti-foaming agents such as octyl alcohol, for example. The presence of such wetting agents has been found to produce a clear chromium deposit eliminating dark mottled deposits and providing for improved coverage in low current density areas.While relatively high concentrations of such wetting agents are not particularly harmful, concentrations greater than about 1 gram per liter have been found in some instances to produce a hazy deposit. Accordingly, the wetting agent when employed is usually controlled at concentrations less than about 1 g/l, with amounts of about 0.05 to about 0.01 g/l being typical.
It is also contemplated that the electrolyte can contain other metals including iron, manganese, and the like in concentrations of from 0 up to saturation or at levels below saturation at which no adverse effect on the electrolyte occurs in such instances in which it is desired to deposit chromium alloy platings. When iron is employed, it is usually preferred to maintain the concentration of iron at levels below about 0.5 g/l.
The electrolyte further contains a hydrogen ion concentration sufficient to render the electrolyte acidic. The concentration of the hydrogen ion is broadly controlled to provide a pH of from about 2.5 up to about 5.5 while a pH range of about 2.8 to 3.5 is particularly satisfactory.
The initial adjustment of the electrolyte to within the desired pH range can be achieved by the addition of any suitable, acid or base compatible with the bath constituents of which hydrochloric or sulphuric acid and/or amonium or sodium carbonate or hydroxide are preferred. During the use of the plating solution, the electrolyte has a tendency to become more acidic and appropriate pH adjustments are effected by the addition of alkali metal and ammonium hydroxides and carbonates of which the ammonium salts are preferred in that they simultaneously replenish the ammonium constituent in the bath.
In accordance with the process aspects of the present invention, the electrolyte as hereina bove described is employed at an operating temperature ranging from about 1 5 to about 45"C, preferably about 20 to about 30"C. Current densities during electroplating can range from about 50 to 250 ASF (5.5 to 27.5 ASD) with densities of about 75 to about 1 50 ASF (8,25 to 16.5 ASD) being more typical. The electrolyte can be employed to plate chromium on conventional ferrous or nickel substrates and on stainless steel as well as nonferrous substrates such as aluminum and zinc.The electrolyte can also be employed for chromium plating plastic substrates which have been subjected to a suitable pretreatment according to well-known techniques to provide an electrically conductive coating thereover such as nickel or-copper layer.
Such plastics include ABS, polyolefin, PVC, and phenol-formaldehyde polymers. The work pieces to be plated are subjected to conventional pretreatments in accordance with prior art practices and the process is particularly effective to deposit chromium platings on conductive substrates which have been subjected to a prior nickel plating operation.
During the electroplating operation, the work pieces are cathodically charged and the bath incorporates a suitable anode of a material which will not adversely effect and which is compatible with the electrolyte composition. For this purpose anodes of an inert material such as carbon, for example, are preferred although other inert anodes of platinized titanium or platinum can also be employed. When a chromium-iron alloy is to be deposited, the anode may suitably be comprised of iron which itself will serve as a source of the iron ions in the bath.
In accordance with a further aspect of the process of the present invention, a rejuvenation of a trivalent electrolyte which has been rendered ineffective or inoperative due to the high concentration of hexavalent chromium ions is achieved by the addition of a controlled effective amount of the metal ion additive agent. Depending upon the specific composition of the trivalent electrolyte, it may also be necessary to add or adjust other constituents in the bath within the broad usable or preferred ranges as hereinbefore specified to achieve optimum plating performance. For example, the rejuvenant may comprise a concentrate containing a suitable metal ion additive agent salt in further combination with halide salts, ammonium salts, borates, and conductivity salts as may be desired or required.The addition of the metal ion additive agent can be effected as a dry salt or as an aqueous concentrate in the presence of agitation to achieve uniform mixing. The time necessary to restore the electrolyte to efficient operation will vary depending upon the concentration of the detrimental hexavalent chromium present and will usually range from a period of only five minutes up to about two or more hours. The rejuvenation treatment can also advantageously employ an electrolytic treatment of the bath following addition of the rejuvenant by subjecting the bath to a low current density of about 10 to about 50 ASF (1.1 to 5.5 ASD) for a period of about 30 minutes to about 24 hours to effect a conditioning or so-called "dummying" of the bath before commercial plating operations are resumed.The concentration of the metal ions to achieve rejuvenation can range within the same limits as previously defined for the operating electrolyte.
In order to illustrate further the composition and process of the present invention, the following specific examples are provided. It will be understood that the examples are provided for illustrative purposes and are not intended to be limiting of the invention as herein disclosed and as set forth in the subjoined claims.
EXAMPLE 1 A trivalent chromium electrolyte is prepared having a composition as set forth below: INGREDIENT CONCENTRATION, g/l Cr+3 22 NH4COOH 40 NH4CI 150 NaBF4 50 H3BO3 50 Nd ions 0.05 Surfactant 0.1 The particular sequence of addition of the bath constituents during bath makeup is not critical in achieving satisfactory performance. The trivalent chromium ions are introduced in the form of chromium sulphate. The neodymium ions are introduced as neodymium trichloride.The surfactant employed comprises a mixture of dihexyl ester of sodium sulpho succinic acid and sodium sulphate derivative of 2-ethyl-1-hexanol. The operating temperature of the electrolyte is from 70 to about 80"F (21-27"C) at cathode current densities of from about 100 to about 250 ASF (11 to 27.5 ASD) and an anode current density of about 50 ASF (5.5 ASD). The electrolyte is employed using a graphite anode at an anode to cathode ratio of about 2:1. The electroplating bath is operated employing a mild air and/or mechanical agitation.It has been found advantageous to subject the bath to an electrolytic preconditioning at a low current density, e.g. about 10 to about 50 ASF (1.1 to 5.5 ASD) for a period up to about 24 hours to achieve satisfactory plating performance at the higher normal operating current densities.
The electrolyte employed under the foregoing conditions produced a full bright and uniform chromium deposit having good to excellent coverage over the current density ranges employed including good coverage in the deep recess areas of the J-type panels employed for test plating.
EXAMPLE 2 This example demonstrates the effectiveness of the neodymium compound for rejuvenating trivalent chromium electrolytes which have been rendered unacceptable or inoperative because of an increase in hexavalent chromiumn concentration to an undesirable level. It has been found by test that the progressive buildup of hexavalent chromium concentration will eventually produce a skipping of the chromium plate and ultimately will result in the prevention of any chromium plate deposite. Such tests employing typical trivalent chromium electrolytes to which hexavalent chromium is intentionally added has evidenced that a concentration of about 0.47 g/l of hexavalent chromium results in plating deposits having large patches of dark chromium plate and smaller areas which are entirely unplated.As the hexavalent chromium concentration is further increased to about 0.55 g/l according to such tests, further deposition of chromium on the substrate is completely prevented. The hexavalent chromium concentration at which plating ceases will vary somewhat depending upon the specific composition of the electrolyte.
In order to demonstrate a rejuvenation of a hexavalent chromium contaminated electrolyte, a trivalent chromium bath is prepared having the following composition: INGREDIENT CONCENTRATION, g/l Sodium fluordborate 110 Ammonium chloride 90 Boric acid 50 Ammonium formate 50 Cr+3 ions 26 Surfactant 0.1 The bath is adjusted to a pH between about 3.5 and 4.0 at a temperature of about 70 to about 80"F (21.1 to 26.7"C). S-shaped nickel plated test panels are plated in the bath at a current density of about 100 ASF(11 ASD). After each test run, the concentration of hexavalent chromium ions is increased from substantially 0 in the original bath by increments of about 0.1 g/l by the addition of chromic acid.No detrimental effects in the chromium plating of the test panels was observed through the range of hexavalent chromium concentration of from 0.1 up to 0.4 g/l. However, as the hexavalent chromium concentration was increased above 0.4 g/l large dark chromium deposits along with small areas devoid of any chromium deposit were observed on the test panels. As the concentration of hexavalent chromium attained a level of 0.55 g/l no further chromium deposit could be plated on the test panel.
Under such circumstances, it has heretofore been common practice to dump the bath containing high hexavalent chromium necessitating a makeup of a new bath which constitutes a costly and time consuming operation.
To demonstrate the rejuvenation aspects of the present invention, neodymium ions were added in increments of about 0.55 g/l to the bath containing 0.55 g/l hexavalent chromium ions and a plating of the test panels was resumed under the conditions as previously described.
The initial addition of 0.55 g/l neodymium ions to the bath contaminated with 0.55 g/l hexavalent chromium ions resulted in a restoration of the efficiency of the chromium plating bath producing a good chromium deposit of good color and coverage although hexavalent chromium ions were still-detected as being present in the bath.
EXAMPLE 3 A basic trivalent chromium electrolyte is prepared having a composition as set forth below: INGREDIENT CONCENTRATION, g/l Cr+3 22 NH4COOH 40 NH4CI 150 NaBF4 50 H3BO3 50 Surfactant 0.1 The trivalent chromium ions are introduced in the form of chromium sulphate. The surfactant employed comprises a mixture of dihexyl ester of sodium sulpho succinic acid and sodium sulphate derivative of 2-ethyl.-l-hexanol. To the foregoing basic trivalent chromium electrolyte, controlled amounts of the reducing metal ions are added in accordance with Examples 4 to 26 and 28 to 37.
EXAMPLE 4 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of gold ions are added in the form of gold chloride (AuCI3). The gold ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible gold compounds including gold bromide (Au Br3), gold iodide (Aul) as well as mixtures thereof.
EXAMPLE 5 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of silver ions are added in the form of silver acetate [Ag(C2H302)]. The silver ions can also be added to the electrolyte employing alternative satisfactory soluble and compatible silver compounds including silver tetraborate (Ag2B407,2H2O), silver-chlorate (AgClO3), silver perchlorate (AgCIO4), silver fluogallate [Ag3(GaF6) 10H20], silver fluoride (AgF), silver fluosilicate (Ag2SiF84H2O) as well as mixtures thereof.
EXAMPLE 6 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of platinum ions are added in the form of platinum chloride (PtCl4). The platinum ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible platinum compounds including platinum trichloride (PtCl3), platinum tetrachloride pentahydrate (PtCI4, 5H2O), platinum tetrafluoride (PtF4), platinum sulphate. [Pt(S04)2,4H20J as well as mixtures thereof.
EXAMPLE 7 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of palladium ions are added in the form of palladium chloride (PdCI2). The palladium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible palladium compounds including palladium chloride dihydrate (PdCI2,2H20), palladium difluoride (Pd F2), palladium sulfate (PdSO4,2H20) as well as mixtures thereof.
EXAMPLE 8 To the trivalent chromium electrolyte of Example 3, -0.05 g/l of rhodium ions are added in the form of rhodium chloride trihydrate (RhCl3,3H2O). The rhodium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible rhodium compounds including rhodium sulphate hydrate [Rh2(SO4)3,XH20], rhodium sulphite [Rh2(SO- 3)3'6H20] as well as mixtures thereof.
EXAMPLE 9 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of iridium ions are added in the form of iridium tetrachloride (IrCI4). The iridium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible iridium compounds including iridium tribromide (IrBr3,4H2O), iridium tetrabromide (IrBr4), iridium dichloride (IrCI2), iridium triiodide ((irk3), iridium sulfate [1r2(S04)3,XH2OJ as well as mixtures thereof.
EXAMPLE 10 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of osmium ions are added in the form of osmium trichloride (OsCI3). The osmium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible osmium compounds including osmium trichloride trihydrate (OsCI3,3H20), osmium tetrachloride (OsCI4), osmium octafluoride (OsF8), osmium tetraoxide (0sO4) as well as mixtures thereof.
EXAMPLE ii To the trivalent chromium electrolyte of Example 3, 0.05 g/l of ruthenium ions are added in the form of ruthenium chloride trihydrate (RuCI3-3H20). The ruthenium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible Ruthenium compounds including ruthenium tetrachloride (RuCl4,5H20), ruthenium hydroxide [Ru(OH)3], ruthenium tetroxide (RuO4) as well as mixtures thereof.
EXAMPLE 12 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of rhenium ions are added in the form of rhenium trichloride (ReCI3). The rhenium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible rhenium compounds including rhenium heptoxide (Re207), rhenium tetrachloride (ReCI4), rhenium hexachloride (ReCI6), rhenium hexafluoride (ReF6) as well as mixtures thereof.
EXAMPLE 13 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of gallium ions are added in the form of gallium trichloride (GaCI3). The gallium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible gallium compounds including gallium acetate [Ga(C2H3O3)3], gallium tribromide (Ga Br3), gallium perchlorate [Ga(C104)3, 6 H20], gallium oxalate [Ga2(C204)3,4H20], gallium selenate [Ga2(Se04)3,22H20, gallium sulphate [Ga2(S04)3, gallium sulphate hydrate [Ga2(SO4)3, 1 8H20] as well as mixtures thereof.
EXAMPLE 14 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of germanium ions are added in the form of germanium chloride (GeCI4). The germanium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible germanium compounds including germanium difluoride (GeF2), germanium tetrafluoride (GeF4,3H20), germanium diiodide (Gel2), germanium tetraiodide (Gel4), germanium dioxide (GeO2) as well as mixtures thereof.
EXAMPLE 15 To the trivalent chromium electrolyte of Example 3, 0.05g/l of indium ions are added in the form of indium chloride (InCI3). The indium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible indium compounds including indium tribromide (In3), indium perchlorate (ln(Cl04)3,8H20], indium fluoride (lnF3,XH20), indium selenate (In2(SeO4)3, 1 0H20J, indium sulphate [In2(SO4)3], indium sulphate nonahydrate [In2(SO 4)3,9H20J, indium dihydrogen sulphate (1n2(S04)3,H2SO4,7H20] as well as mixtures thereof.
EXAMPLE 16 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of samarium ions are added in the form of samarium chloride hexahydrate (SmCl3,6H20). The samarium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible samarium compounds including samarium acetate Sm(C2H3O2)3 3H2O], samarium bromate [Sm(BrO 3)39H2O], samarium chloride (SmC13), samarium sulfate Sm2(S04)3,8H20J, as well as mixtures thereof.
EXAMPLE 17 To the trivalent chromium electrolyte of Example 3, 0.05 g/I of europium ions are added in the form of europium sulphate octohydrate [Eu2(SO4)3,8H2O]. The europium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible europium compounds as well as mixtures thereof.
EXAMPLE 18 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of gadolinium ions are added in the form of gadolinium chloride hexahydrate (GdCl3,6H20). The gadolinium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible gadolinium compounds including gadolinium acetate [Gd(C2H3O2)3,4H20J, gadolinium bromide [GdBr3,6H20], gadolinium chloride (GdCI3), gadolinium oxide (Gd203), gadolinium selenate [Gd2(Se04)3,8H20], gadolinium sulphate [Gd2(S04)3J, gadolinium sulphate octahydrate [Gd2(SO 4)3,8H20] as well as mixtures thereof.
EXAMPLE 19 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of terbium ions are added in the form of terbium trichloride hexahydrate (TbCI36H2O). The terbium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible terbium compounds including terbium chloride (TbCI3), terbium oxide (Tb2O3), terbium sulphate [Tb2(SO4)38H20] as well as mixtures thereof.
EXAMPLE 20 To the trivalent chromium electrolyte of Example 3; 0.05 g/l of dysprosium ions are added in the form of dysprosium trichloride (DyCI3). The dysprosium ions can-also be added to the electrolyte employing alternative satisfactory bath soluble and compatible ysprosium compounds including dysprosium acetate Dy(C2H302)3,4H20J, dysprosium bromate Dy(Br03)3,9H3OJ, dysprosium oxide (Dy2O3), dysprosium selenate Dy2-(SeO4)3,8H20J, dysprosium sulphate [Dy2(SO- 4)3,8H30J as well as mixtures thereof.
EXAMPLE 21 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of holmium ions are added in the form of holmium trichloride hexahydrate (HoCl3,6H2O). The holmium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible holmium compounds as well as mixtures thereof.
EXAMPLE 22 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of erbium ions are added in the form of erbium trichloride hexahydrate (ErCI3,6H2O). The erbium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible rbium compounds including erbium sulphate Er2(SO4)3), erbium sulphate octahydrate (Er2(SO4)38H2O] as well as mixtures thereof.
EXAMPLE 23 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of thulium ions are added in the form of thulium trichloride (TmCl3). The thulium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible thulium compounds as well as mixtures thereof.
EXAMPLE 24 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of ytterbium ions are added in the form of ytterbium trichloride hexahydrate (YbCI3,6H3O). The ytterbium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible ytterbium compounds including ytterbium acetate [Yb(C2H3O2)3,4H2O], ytterbium sulphate [Yb2(SO4)3], ytterbium sulphate octahydrate [Yb3(S04)3,8H30] as well as mixtures thereof.
EXAMPLE 25 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of lutetium ions are added in the form of lutetium sulphate octahydrate [Lu2(SO4)3 8H20]. The lutetium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible lutetium compounds as well as mixtures thereof.
EXAMPLE 26 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of praseodymium ions are added in the form of praseodymium sulphate octahydrate LPr2(S0J3,8H2O]. The praseodymium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible praseodymium compounds including praseodymium acetate [Pr(C2H302)3 3H20], praseodymium bromate [Pr(BrO3)3,9H30, praseodymium chloride (PrCI3), praseodymium chloride (PrC1,7H,O), praseodymium selenate [Pr2(SeO4)3l, praseodymium sulphate [Pr2(SO4)3], praseodymium sulphate pentahydrate [Pr2(S04)3,5H20J as well as mixtures thereof.
EXAMPLES 27A-27W This example demonstrates the effectiveness of the metal ion reducing agents for rejuvenating trivalent chromium electrolytes which have been rendered unacceptable or inoperative because of an increase in hexavalent chromium concentration to an undesirable level. It has been found by test that the progressive buildup of hexavalent chromium concentration will eventually produce a skipping of the chromium plate and ultimately will result in the prevention of any chromium plate deposit. Such tests employing typical trivalent chromium electrolytes to which hexavalent chromium is intentionally added has evidenced that a concentration of about 0.4 g/l of hexavalent chromium results in plating depositing having large patches of dark chromium plate and smaller areas which are entirely unplated.As the hexavalent chromium concentration is further increased to about 0.55 g/l according to such tests, further deposition of chromium on the substrate is completely prevented. The hexavalent chromium concentration at which plating ceases will vary somewhat depending upon the specific composition of the electrolyte.
In order to demonstrate a rejuvenation of a hexavalent chromium contaminated electrolyte, a trivalent chromium bath is prepared having the following composition: INGREDIENT CONCENTRATION, g/l Sodium fluoroborate 110 Ammonium chloride 90 Boric acid 50 Ammonium formate 50 Cr+3 ions 26 Surfactant 0.1 The bath is adjusted to a pH between about 3.5 and 4.0 at a temperature of about 70 to about 80"F (21.1 to 26.7"C). S-shaped nickel plates test panels are plated in the bath at a current density of about 100 ASF (11 ASD). After each test run, the concentration of hexavalent chromium ions is increased from substantially 0 in the original bath by increments of about 0.1 g/l by the addition of chromic acid.No detrimental effects in the chromium plating of the test panels was observed through the range of hexavalent chromium concentration of from 0.1 up to 0.4 g/l. However, as the hexavalent chromium concentration was increased above 0.4 g/l large dark chromium deposits along with small areas devoid of any chromium deposit were observed on the test panels. As the concentration of hexavalent chromium attained a level of 0.55 g/l no further chromium deposit could be plated on the test panel.
Under such circumstances, it has heretofore been common practice to dump the bath containing high hexavalent chromium necessitating a makeup of a new bath which constitutes a costly and time consuming operation.
To demonstrate the rejuvenation aspects of the present invention, reducing metal ions as described in Examples 4 through 26 were added in increments of about 0.55 g/l to the bath containing 0.55 g/l hexavalent chromium ions and a plating of the test panels was resumed under the conditions as previously described.
In each instance, the initial addition of 0.55 g/l of the individual reducing metal ions to the bath contaminated with 0.55 g/l hexavalent chromium ions resulted in a restoration of the efficiency of the chromium plating bath producing a good chromium deposit of good colour and coverage although hexavalent chromium ions were still detected as being present in the bath.
EXAMPLE 28 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of scandium ions are added in the form of scandium trichloride hexahydrate (ScCl3,6H2O). The scandium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible scandium compounds including scandium chloride (ScCI3), scandium sulphate CSc,(SO,),I, scandium sulphate pentahydrate SQ(SO4)3,5H2OJ, scandium sulphate hexahydrate [Sc2(SO4)3,6H20J as well as mixtures thereof.
EXAMPLE 29 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of yttrium ions are added in the form of yttrium trichloride hexahydrate (YCI3,6H20). The yttrium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible yttrium compounds including yttrium acetate rY(C2H3O2)3,4H2O1, yttrium bromate (BrO3)3,9H2O], yttrium bromide (YBr3), yttrium bromide nonahydrate (YBr3,9H2O), yttrium chloride (YCI3), yttrium chloride monohydrate (YCI3,H2O), yttrium iodide (Yl3), yttrium oxalate [YAC2O4)3,9H201, yttrium oxide (Y203), yttrium sulphate [Y2(SO4)3], yttrium sulphate oxtahydrate Y2(SO4)3,8H2OJ as well as mixtures thereof.
EXAMPLE 30 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of lanthanium ions are added in the form of lanthanum trichloride heptahydrate (LaCI3,7H20). The lanthanum ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible lanthanum compounds including lanthanum acetate La(C2H3O2)3 1 +H20], lanthanum bromate La(BrO3)3 9 H2OJ, lanthanum bromide [LaBr3 7H20), lanthanum carbonate LLaACO3)3 8H20], lanthanum chloride (LaCI3), lanthanum hydroxide [La(OH)3J, lanthanum iodate [La(103)3], lanthanum molybdate (La(MoO4)3], lanthanum oxide (La2O3), lanthanum sulphate [La2(SO4)3], lanthanum sulphate nonahydrate LLa2(SO4)3,9H2-O] as well as mixtures thereof.
EXAMPLE 31 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of titanium ions are added in the form of titanium trichloride (TiCI3). The titanium.ions can also be added tb the electrolyte employing alternative satisfactory bath soluble and compatible titanium compounds including titanium tribromide (TiBr3,6H20), titanium tetrachloride (TiCI4), titanium trifluoride (TiF4), titanium iodide (Til4), titanium oxalate [Ti2(C204)3 1 0H20], titanium dioxide (TiO2,XH2O) as well as mixtures thereof.
EXAMPLE 32 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of hafnium ions are added in the form of hafnium oxychloride octahydrate (HfOCI2 8H20). The hafnium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible hafnium compounds and mixtures thereof.
EXAMPLE 33 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of arsenic ions are added in the form of arsenic oxide (As2O5).- The arsenic ions can also be added to the electrolyte employing alternative satisfactory bath soluble and'compatible arsenic compounds including arsenic pentafluoride (ass5), arsenic trioxide (As2O3) as well as mixtures thereof.
EXAMPLE 34 To the trivalent chromium electrolyte of Example. 3, 0.05 g/l of selenium ions are added in the form of sodium selenate (Na2SeO4). The selenium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible selenium compounds including sodium selenate hydrate (Na2SeO4,10H20), sodium selenite (Na2SeO3,5H3O), selenium dioxide (SeO2), potassium selenate (K2SeO4), potassium selenite (K2SeO3) as well as mixtures thereof.
EXAMPLE 35 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of tellurium ions are added in the form of sodium tellurium oxide dihydrate (Na2TeO4,2H2O). The tellurium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible tellurium compounds including potassium orthotellurate (K2H4TeO6,3H2O), potassium telluride (kite), potassium tellurite (K2TeO3), sodium orthotellurate (Na2H4TeO6), sodium tellurite (Na2TeO3) as well as mixtures thereof.
EXAMPLE 36 To the trivalent chromium electrolyte of Example 3, 0.05 g/l of cerium ions are added in the form of cerium sulphate (Ce2(S04)3). The cerium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and compatible cerium compounds including cerium acetate [Ce(C2H302)2j, cerium bromate [Ce(BrO3,9H2Oi, cerium carbonate [Ce2(CO3)3,5H20], cerium chloride (CeC13), cerium iodide (Cel3,9H2O), cerium molybdate.[Ce2(Mo04)3], cerium selenate [Ce2(SeO4)3], cerium sulphate tetrahydrate [Ce2(S04)3,4H2OJ, cerium sulphate octåhydrate (Ce2(S04)3,8H2 Oj, cerium sulphate nonahydrate [Ce2(S04)3,9H2Oj as well as mixtures thereof.
EXAMPLE 37 To the trivalent chromium electrnlyte of Example 3, 0.05 g/l of uranium ions are added in the form of uranium oxysulphate hydrate (UO2(SO4)'3H2O). The uranium ions can also be added to the electrolyte employing alternative satisfactory bath soluble and-compatible uranium compounds including uranium tribromide (UBr3), uranium tetrabromide (U Br6), uranium trichloride (UCI3), uranium tetrachloride (UC14);; uranium tetraiodide (us,), uranyl acetate [UO2(C2H30- 2)2,2H20], uranyl bromide (UO2Br2), uranyl chloride (UO2CI2), uranyl formate [U02(CHO3)2,l'l20,- uranyl iodate [UO2(103)2 H20], uranyl oxalate [UO2C20 4,3H20], uranyl sulphate heptahydrate (2U02SO4 7H20) as well as mixtures thereof.
The electrolyte of Examples 4 to 26 and 28 to 37 were employed at an operating temperature of from about 70 to about 80"F (21-27"C) at cathode current densities of from about 100 to about 250 ASF (11 to 27.5 ASD) and an anode current density of about 50 ASF (5.5 ASD).
The electrolyte is employed using a graphite anode at an anode to cathode ratio of about 2:1.
The electroplating bath is operated employing mild air and/or mechanical agitation. In each instance, it has been found advantageous to subject the bath to an electrolytic preconditioning at a low current density, e.g. about 10 to about 50 ASF (1.1 to 5.5 ASD) for a period up to about 24 hours to achieve satisfactory plating performance at the higher normal operating current densities.
The electrolytes incorporating the additive metal ions in accordance with Examples 4-26 and 28-37 under the foregoing operating conditions product full bright and uniform chromium deposits having good to excellent coverage over the current density ranges employed including good coverage in the deep recess areas of the J-type panels employed for test plating.
EXAMPLES 38A-38J This example demonstrates the effectiveness of the metal ion additive agents for rejuvenating trivalent chromium electrolytes which have been rendered unacceptable or inoperative because of an increase in hexavalent chromium concentration to an undesirable level. It has been found by test that the progressive buildup of hexavalent chromium concentration will eventually produce a skipping of the chromium plate and ultimately will result in the prevention df any chromium plate deposit. Such tests employing typical trivalent chromium electrolytes to which hexavalent chromium is intentionally added has evidenced that a concentration of about 0.47 g/l of hexavalent chromium results in plating deposits having large patches of dark chromium plate and smaller areas which are entirely unplated.As the hexavalent chromium concentration is further increased to about 0.55 g/l according to such tests, further deposition of chromium on the substrate is completely prevented. The hexavalent chromium concentration at which plating ceases will vary somewhat depending upon the specific composition of the electrolyte.
In order to demonstrate a rejuvenation of a hexavalent chromium contaminated electrolyte, a trivalent chromium bath is prepared having the following composition: INGREDIENT CONCENTRATION, g/l Sodium fluoroborate 110 Ammoniumn chloride 90 Boric acid 50 Ammonium formate 50 Cr+3 ions 26 Surfactant 0.1 The bath is adjusted to a pH between about 3.5 and 4.0 at a temperature of about 70 to about 80"F (21 to 27"C). S-shaped nickel plated test panels are plated in the bath at a current density of about 100 ASF (11 ASD). After each test run, the concentration of hexavalent chromium ions is increased from substantially 0 in the original bath by increments-of about 0.1 g/l by the addition of chromic acid.No detrimental effects in the chromium plating of the test panels was observed through the range of hexavalent chromium concentration of from 0.1 up to 0.4 g/l. However, as the hexavalent chromium concentration was increased above 0.4 g/l large dark chromium deposits along with small areas devoid of any chromium deposit were observed on the test panels. As the concentration of hexavalent chromium attained a level of 0.55 g/l no further chromium deposit could be plated on the test panel.
Under such circumstances, it has heretofore been common practice to dump the bath containing high hexavalent chromium necessitating a makeup of a new bath which constitutes a costly and time consuming operation.
To demonstrate the rejuvenation aspects of the present invention, additive metal ions as described-in Examples 28 to 37 were added in increments of about 0.55 g/l to the bath containing 0.55 g/l hexavalent chromium ions and a plating of the test panels-was resumed under the conditions as previously described.
In each instance, the initial addition of 0.55 g/l of the individual additive metal ion;s to-t bath conlaminated with 0.55 g/l hexavalent chromium ions resulted in a restoration of the efficiency of the chromium plating bath producing a good chromium deposit of good coföur~and coverage although hexavalent chromium ions were still detected as being present in the bath While it will be apparent that the invention herein disclosed is well calculated to achieve the benefits and advantages as hereinabove set forth, it will be appreciated that the invention ib susceptible to modification, variation and change without departing from the spirit thereof.

Claims (32)

1. An aqueous acidic trivalent chromium electrolyte containing trivalent chromium ions, a complexing agent for maintaining the trivalent chromiumions in solution, halide ions, ammonium ions, hydrogen ions to provide a pH on the acid side, and an additive agent comprising one or more metal ions seleced from neodymium, gold, silver, platinum, palladium, rhodium, iridium, osmium, ruthenium, rhenium, gallium, germanium, indium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, praseodymiumn, scandium, yttrium, lanthanum, titanium; hafnium, arsenic, selenium, tellurium, cerium and uraniurri.
2. An electrolyte as claimed in Cliam.1 in which the trivalent chromium ions are present in an amount of 0.2 to 0.8 molar.
3. An electrolyte as claimed in Claim 1 or 2 in which the trivalent chromium ions are present in an amount of 0.4 to 0.6 molar.
4. An electrolyte as claimed in Claim 1, 2 or 3 in which the complexing agent is present in a molar ratio of complexing agent to chromium ions of from 1:1 to 3:1.
5. An electrolyte as claimed in any one of Claims 1 to 4 in which the complexing agent is present in a molar ratio of complexing agent to chrornium ions of from 1.5:1 to 2:1.
6. An electrolyte as claimed in any one of Claims 1 to 5, in which the ammonium ions are present in an amount to provide a molar ratio of ammonium ions to chromium ions ranging from 2.0:1 to about 11:1.
7. An electrolyte as claimed in any one of Claims 1 to 6, in which the ammonium ions are present in an amount to provide a molar ratio of ammonium ions to chromium ions ranging from 3:1 to 7:1.
8. An electrolyte as claimed in any one of Claims 1 to 7 in which the halide ions are present in an amount to provide a molar ratio of halide ions to chromium ions of from 0.8:1 to 10:1.
9. An electrolyte as claimed in any one of Claims 1 to 8, in which the halide ions are present in an amount to provide a molar ratio of halide ions to chromium ions of from 2:1 to 4:1.
10. An electrolyte as claimed in any one of Claims 1 to 9, containing conductivity salts.
11. An electrolyte as claimed in Cliam 10 in which the conductivity salts are present in an amount up to 400 g/l.
12. An electrolyte as claimed in any one of Claims 1 to 11, further containing borate ions.
1 3. An electrolyte as claimed in any one of Claims 1 to 12, further containing a surfactant.
1 4. An electrolyte as claimed in any one of Claims 1 to 13, in which the hydrogen ions are present to provide a pH of 2.5 to 5.5.
1 5. An electrolyte as claimed in any one of Claims 1 to 14, in which the metal ion additive agent comprises a metal ion selected from scandium present in an amount of 0.02 to 20 g/l, yttrium present in an amount of 0.025 to 20 g/l; lanthanum present in an amount of 0.01 to 20 g/l; titanium present in an amount of 0.01 to 20 g/l; hafnium present in an amount of 0.015 to 15 g/l; arsenic present in an amount of 0.025 to 10 g/l; selenium present in an amount of 0.025 to 10 g/l; tellurium present in an amount of 0.025 to 10 g/l; cerium present in an amount of 0.002 to 10 g/l; uranium present in an amount of 0.003 to 10 g/l; and mixtures therof.
16. An electrolyte as claimed in any one of claims 1 to 15, in which the metal ion additive agent comprises a metal ion selected from scandium present in an amount of 0. 1 to 1 g/l; yttrium present in an amount of 0.1 to 1 g/l; lanthanum present in an amount of 0.1 to 1 g/l; titanium present in an amount of 0.1 to 1 g/l; hafnium present in an amount of 0.1 to 1 g/l; arsenic present in an amount of from 0. 1 to 1 g/l; selenium present in an amount of 0.1 to 1 g/l; tellurium present in an amount of 0.1 to 1 g/l; cerium present in an amount of 0.05 to 1 g/l; and mixtures thereof.
1 7. An electrolyte as claimed in any one of Claims 1 to 16, in which the metal ion additive agent comprises neodymium ions present in an amount 0.005 to 1 7 g/l.
1 8. An electrolyte as claimed in any one of Claims 1 to 17, in- which the metal ion additive agent comprises neodymium ions present in an amount of 0.05 to 5 g/l.
19. An electrolyte as defined in any one of Claims 1 to 14, in which the metal additive agent comprises a metal ion selected from gold present in an amount of 0.004 to 5 g/l; silver present in an amount of 0.003 to 10 g/l; platinum present in an amount of 0.002 to 10 g/l; palladium present in an amount of 0.002 to 10 g/l; rhodium present in an amount of 0.002 to 10 g/l; iridium present in an amount of 0.002 to 10 g/l; osmium present in an amount of 0.001 to 10 g/l; ruthenium present in an amount of 0.025 to 10 g/l; rhenium present in an amount of 0.025 10 g/l; gallium present in an amount of 0.060 to 10 g/l; germanium present in an amount of 0.020 to 10 g/l; indium present in an amount of 0.030 to 10 g/l; samarium present in an amount of 0.020 to 10 g/l; europium present in an amount of 0.020 to 10 g/l; gadolinium present in an amount of 0.002 to 10 g/l; terbium present in an amount of 0.002 to 10 g/l; dysprosium present in an amount of 0.002 to 10 g/l; holmium present in an amount of 0.002 to 10 g/l; erbium present in an amount of 0.002 to 10 g/l; thulium present in an amount of 0.002 to 10 g/l; ytterbium present in an amount of 0.002 to 10 g/l; lutetium present in an amount of 0.002 to 10 g/l; praseodymium present in an amount of 0.002 to 10 g/l; and mixtures thereof.
20. An electrolyte as claimed in any one of Claims 1 to 14, in which the metal ion additive agent comprises a metal ion selected from gold present in an amount of 0.025 to 2 g/l; silver present in an amount of 0.025 to 2 g/l; platinum present in an amount of 0.025 to 1 g/l; palldium present in an amount of 0.025 to 1 g/l; rhodium present in an amount of 0.025 to 1 g/l; iridium present in an amount of 0.025 to 1 g/l osmium present in an amount of 0.02 to 1 g/l; ruthenium present in an amount of 0.1 to 1 g/l; rhenium present in an amount of 0.1 to 1 g/l; gallium present in an amount of 0.1 to 1 g/l; germanium present in an amount of 0.1 to about 1 g/l; indium present in an amount of 0.05 to 1 g/l; samarium present in an amount of 0.05 to 1 g/l; europium present in an amount of 0.05 to 1 g/l; gadolinium present in an amount of 0.05 to 1 g/l: terbium present in an amount of 0.05 to 1 g/l; dysprosium present in an amount of 0.05 to 1 g/l; holmium present in an amount of 0.05 to 1 g/l; erbium present in an amount of 0.05 to 1 g/l; thulium present in an amount of 0.05 to 1 g/l; ytterbium present in an amount of 0.05 to 1 g/l; lutetium present in an amount of 0.05 to 1 g/l; praseodymium present in an amount of 0.05 to 1 g/l; and mixtures thereof.
21. An electrolyte as claimed in any one of Claims 1 to 20, in which the trivalent chromium ions are present in an amount of 0.2 to 0.8 molar, the complexing agent is present in a molar ratio of complexing agent to chromium ions of 1:1 to 3:1, the halide ions are present in a molar ratio of halide ions to chromium ions of 0.8:1 to 10:1, the ammonium ions are present in a molar ratio of ammonium ions to chromium ions of 2.0:1 to 11:1, the hydrogen ions are present in an amount to provide a pH of 2.5 to 5.5, and the metal ion additive agents are present in an amount of 0.001 to 30 g/l.
22. An electrolyte as claimed in any one of Claims 1 to 21, in which the trivalent chromium ions are present in an amount of 0.4 to 0.6 molar, the complexing agent is present in a molar ratio of complexing agent to chromium ions of 1.5:1 to 2:1, the halide ions are selected from chloride, bromide and mixtures thereof present in an amount to provide a molar ratio of halide ions to chromium ions of 2:1 to 4: 1, the ammonium ions are present in an amount to provide a molar ratio of ammonium ions to chromium ions of 3:1 to 7:1, the hydrogen ions are present to provide a pH of 2.8 to 3.5 and the metal ion additive agents are present in an amount of 0.02 to 5 g/l
23. An electrolyte as claimed in Claim 1 substantially as herein described with reference to any one of the examples.
24. A process for electroplating a chromium deposit on an electrically conductive substrate comprising the step of immersing the substrate in an aqueous acidic trivalent chromium electrolyte as defined in any one of Claims 1 to 23, applying a cathodic charge to the substrate to effect a progressive deposition of a chromium electrodeposit thereon, and continuing the electrodeposition of the chromium electrodeposit until the desired thickness is obtained.
25. A process for rejuvenating an aqueous acidic trivalent chromium electrolyte which has been impaired in effectiveness due to the contamination by excessive quantities of hexavalent chromium, the electrolyte containing trivalent chromium ions, a complexing agent for maintaining the trivalent chromium ions in solution, halide ions, ammonium ions and hydrogen ions to provide a pH on the acid side, the process comprising the steps of adding to the electrolyte an additive agent comprising a metal ion selected from neodymium, gold, silver, platinum, palladium, rhodium, iridium, osmium, ruthenium, rhenium, gallium, germanium, indium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, praseodymium, scandium, yttrium, lanthanum, titanium, hafnium, arsenic, selenium, tellurium, cerium, uranium and mixtures thereof, in an amount sufficient to reduce the concentration of hexavalent chromium ions to a level at which the effectiveness of the electrolyte to deposit satisfactory chromium deposits is restored.
26. A process for rejuvenating an acidic trivalent-chromium electrolyte substantially as herein described with reference to any one of the exaples.
27. An article whenever plated by means of an electrolyte as claimed in any one of Claims 1 to 23, and/or by a proces as claimed in Claim 24 and/or by means of an electrolyte which has been rejuvenated by a process as claimed in Claim 25.
28. An aqueous acidic trivalent chromium electrolyte containing chromium ions, a complexing agent for maintaining the trivalent chromium ions in solution, halide ions, ammonium ions, hydrogen ions to provide a pH on the acid side, and an additive agent comprising one or more metal ions selected from scandium, titanium, yttrium, lanthanium and hafnium.
29. An aqueous acidic trivalent chromium electlo;,-te containing chromium ions, a complexing agent for maintaining the trivalent chromium ions in soluton, halide ions, ammonium ions, hydrogen ions to provide a pH on the acid side, and an additive agent comprising one or more metal ions selected from ruthenium, rhenium, palladium, silver, rhodium, osmium, iridium, platinum and gold.
30. An aqueous acidic trivalent chromium electrolyte containing chromium ions, a complexing agent for maintaining the trivalent chromium ions in solution, halide ions, ammonium ions, hydrogen ions to provide a pH on the acid side, and an additive agent comprising one or more metal ions selected from gallium, germanium, arsenic, selenium, indium and tellurium.
31. An aqueous acidic trivalent chromium electrolyte containing chromium ions, a complexing agent for maintaining the trivalent chromium ions in solution, halide ions, ammonium ions, hydrogen ions to provide a pH on the acid side, and an additive agent comprising one or more lanthanide metal ions.
32. An aqueous acidic trivalent chromium electrolyte containing chromium ions, a complexing agent for maintaining the trivalent chromium ions in solution, halide ions, ammonium ions, hydrogen ions to provide a pH on the acid side, and an additive agent comprising uranium ions.
GB08412122A 1983-05-12 1984-05-11 Trivalent chromium electroplating electrolytes rejuvenation thereof Expired GB2141138B (en)

Applications Claiming Priority (3)

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US06/492,303 US4477318A (en) 1980-11-10 1983-05-12 Trivalent chromium electrolyte and process employing metal ion reducing agents
US06/492,304 US4439285A (en) 1980-11-10 1983-05-12 Trivalent chromium electrolyte and process employing neodymium reducing agent
US06/492,302 US4477315A (en) 1980-11-10 1983-05-12 Trivalent chromium electrolyte and process employing reducing agents

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GB8412122D0 GB8412122D0 (en) 1984-06-20
GB2141138A true GB2141138A (en) 1984-12-12
GB2141138B GB2141138B (en) 1986-07-09

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ES (1) ES8603592A1 (en)
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WO2007115030A1 (en) * 2006-03-31 2007-10-11 Atotech Deutschland Gmbh Crystalline chromium deposit
WO2009046181A1 (en) * 2007-10-02 2009-04-09 Atotech Deutschland Gmbh Crystalline chromium alloy deposit
EP3106544A4 (en) * 2014-02-11 2017-08-09 Muñoz Garcia, Carlos Enrique Continuous trivalent chromium plating method
EP4151779A1 (en) * 2021-09-15 2023-03-22 Trivalent Oberflächentechnik GmbH Chrome-indium, chrome-bismuth and chrome antimony coating, method for the production and use thereof

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AT510422B1 (en) * 2010-11-04 2012-04-15 Univ Wien Tech METHOD FOR THE DEPOSITION OF HARTCHROM FROM CR (VI) - FREE ELECTROLYTES
CN108808030B (en) * 2018-07-03 2023-08-08 重庆大学 Pulsed battery design based on B-Z oscillation reaction

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Publication number Priority date Publication date Assignee Title
WO2007115030A1 (en) * 2006-03-31 2007-10-11 Atotech Deutschland Gmbh Crystalline chromium deposit
US7887930B2 (en) 2006-03-31 2011-02-15 Atotech Deutschland Gmbh Crystalline chromium deposit
WO2009046181A1 (en) * 2007-10-02 2009-04-09 Atotech Deutschland Gmbh Crystalline chromium alloy deposit
US8187448B2 (en) 2007-10-02 2012-05-29 Atotech Deutschland Gmbh Crystalline chromium alloy deposit
EP3106544A4 (en) * 2014-02-11 2017-08-09 Muñoz Garcia, Carlos Enrique Continuous trivalent chromium plating method
EP4151779A1 (en) * 2021-09-15 2023-03-22 Trivalent Oberflächentechnik GmbH Chrome-indium, chrome-bismuth and chrome antimony coating, method for the production and use thereof
WO2023041670A1 (en) * 2021-09-15 2023-03-23 Trivalent Oberflächentechnik Gmbh Chromium-indium, chromium-bismuth and chromium-antimony coatings, method for the production and use thereof

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GB8412122D0 (en) 1984-06-20
ES532467A0 (en) 1985-12-16
DE3417416A1 (en) 1984-11-22
CA1244376A (en) 1988-11-08
GB2141138B (en) 1986-07-09
FR2545841A1 (en) 1984-11-16
BR8402245A (en) 1984-12-18
ES8603592A1 (en) 1985-12-16
AU2796484A (en) 1984-11-15
DE3417416C2 (en) 1988-07-07

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