US3337430A - Ultrahigh-speed chromium electrodeposition - Google Patents

Ultrahigh-speed chromium electrodeposition Download PDF

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Publication number
US3337430A
US3337430A US300107A US30010763A US3337430A US 3337430 A US3337430 A US 3337430A US 300107 A US300107 A US 300107A US 30010763 A US30010763 A US 30010763A US 3337430 A US3337430 A US 3337430A
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United States
Prior art keywords
bright
chromium
chromic acid
limits
proportion
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Expired - Lifetime
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US300107A
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English (en)
Inventor
Johnson Andy Albert
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M&T Chemicals Inc
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M&T Chemicals Inc
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Publication date
Application filed by M&T Chemicals Inc filed Critical M&T Chemicals Inc
Priority to US300107A priority Critical patent/US3337430A/en
Priority to GB31366/64A priority patent/GB1079646A/en
Priority to NL6408934A priority patent/NL6408934A/xx
Priority to DE1964M0062006 priority patent/DE1496903B2/de
Priority to JP39044781A priority patent/JPS4927017B1/ja
Application granted granted Critical
Publication of US3337430A publication Critical patent/US3337430A/en
Anticipated expiration legal-status Critical
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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
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/04—Electroplating: Baths therefor from solutions of chromium

Definitions

  • Chromium plating has found wide use as a means for producing a bright, durable, decorative coating on various articles.
  • the high luster which is produced thereon greatly enhances the attractiveness, serviceability, and aesthetic appeal of the plated article.
  • cathode current densities have, in practice, been limited to about 3-75 amperes per square decimeter (a.s.d.) at which level only about .02-.5 micron of bright chromium is deposited per minute.
  • a satisfactory bath for plating bright chromium at very high speeds should be capable of producing a thickness of about 5 microns of bright chromium plate at a rate of at least about 1.25, and preferably at least about 2.5 microns per minute. Thus, not only must the plating speed be high, but the plate must remain bright until a desirable commercial thickness is obtained.
  • bright in describing bright chromium electrodeposits is limited to surfaces which have suificient reflectivity to render a well defined and recognizable image.
  • the bright range of deposits is also divided into two subdivisions-deposits referred to as .rnirror-bright and deposits referred to as bright.
  • mirror-bright deposits are those which have the reflectivity ordinarily associated with a good mirror.
  • the bright deposits have a lesser degree of reflectivity than a good mirror, but sufiicient reflectivity to render a well defined and recognizable image.
  • These bright deposits are sufficiently bright as plated to be acceptable decorative finishes. Their degree of brightness may be improved by a buffing operation to achieve mirror brightness.
  • the term bright chromium encompasses those deposits which are mirror-bright and bright, as defined herein.
  • this invention relates to novel chromium electroplating baths containing chromic acid and sulfate characterized by their ability to produce bright chromium plate at very high plating speeds, wherein the variables chromic acid concentration, ratio, proportion, and temperature are within the limits CrO g./l 100-400 Ratio 25-100 Proportion 0-4 Temperature C 27-94 and wherein at least two of said variables are within the limits CrO g./l 150-250 Ratio 25-70 Proportion 0-2 Temperature C 60-82
  • the process of this invention is particularly suitable for plating bright chromium at very high plating speeds, i.e., at deposition rates of at least about 1.25 microns per minute.
  • this invention permits attainment of plating speeds of greater than 2.5 microns per minute and even as high as about 10 microns per minute.
  • practice of this invention gives results which are 2.5 to 20 times faster than those commonly obtained from prior art processes.
  • the chromium plate obtained at these very high plating speeds may be bright and lustrous, a result which has not heretofore been attainable.
  • the chromium plating baths which may find use in the practice of this invention may typically comprise water, chromic acid (CrO and sulfate ion (which may have been added as sulfuric acid or salts thereof).
  • the baths may contain active fluoride, or complex fluorides suchv as silicofluorides, fluoaluminates, fluozirconates, fiuotitanates, etc., and fume-suppressants, etc.
  • the plating apparatus which is employed in conjunction with these baths may include a regulatable source of electric current, an anode which may typically be a lead anode, and a catho-de on which chromium metal is electrodeposited.
  • a chromium plating bath may be described by reference to various parameters including:
  • Ratio (which is here taken as the numerical value obtained by dividing the chromic acid concentration by the sum of the concentrations of the catalyst anions, such as sulfate ion and silicofluoride ion, all of which are expressed in grams per liter),
  • Proportion (which is the numerical value obtained by dividing the silicofiuoride or other complex fluoride ion concentration by the sulfate ion concentration, both of which are expressed in grams per liter),
  • the desirably high, bright plating speeds may be realized if four of the bath variables, viz. chromic acid concentration, ratio, proportion, and temperature are maintained within certain narrow limits and at least two of said variables are maintained within certain specific limits. Although any two of these variables may be within the specific limits, preferably the chromic acid concentration and/or temperature will be. Preferably at least 3 of said variables may be maintained within the specific limits.
  • the chromic acid concentration in the novel baths may fall within the narrow limits of 100-400 grams per liter (g./l.) and specific limits of 150-250 g./l.
  • the narrow limits may be about 100-300 g./l.
  • the ratio of the novel baths of this invention may fall within the narr-o-w limits 25-100 and the specific limits 25-70.
  • the narrow limits may be about 25-90 and the specific limits may be about 40-60, say 50.
  • the proportion of the novel baths may typically be maintained within the narrow limits 0-4 and the specific limits 0-2.
  • the narrow limits may be 0-3 and the specific limits may be 0-1, say 0.
  • Bath temperature may typically be maintained within narrow limits 27-94 C. and specific limits 60-82" C.
  • the narrow limit may be 49-88 C.
  • the specific limits may be 60-77 C. say 65 C.
  • the novel chromium electroplating baths of this invention may be capable of producing bright chromium plate at high plating speeds when electrolyzed at high cathode current densities.
  • High cathode current densities may be those greater than about 150 a.s.d.
  • the novel baths may be electrolyzed at about 150-600, say 300 a.s.d., the particular current density being chosen in accordance with the high plating speed desired. It is an outstanding feature of this invention that the high current densities which may be employed may permit attainment of bright chromium plate at very high rates of deposition.
  • the very high rates of deposition obtained by practice of this invention may be advantageous in the plating of bright, decorative chromium plate of varying thicknesses.
  • Preferred embodiments of the invention may produce as much as about microns per minute of bright chromium plate.
  • a bath having the composition CrO g./l 275 Ratio 40 Proportion 3 was made up and maintained at an operating temperature of 71 C.
  • the temperature and ratio variables were within their respective specific limits and the chromic acid concentration and proportion were outside their specific limits but within their narrow limits.
  • Nickel-plated brass panels were employed as cathodes and a lead anode 4 was used.
  • the systems were electrolyzed at a cathode current density of 150, 300, 450 and 600 a.s.d. for a total of one minute and the thickness of bright chromium plate deposited was measured. The results are shown in Table I wherein thickness is given in microns.
  • a Hull cell test was employed to determine the maximum thickness of bright chromium plate which could be obtained from various plating solutions during one minute of electrolysis. Because of the construction of the Hull cell, the current density over the length of the cathode is systematically varied. Standard nickelplated brass Hull cell panels were masked so that only a 5 mm. strip was exposed to the bath in order to obtain the high cathode current densities required for high speed chromium plating. Chromium plating solutions which exemplify those falling within the scope of this invention were prepared by dissolving the desired amounts of chromic acid, sulfuric acid and fiuosilicic acid (H SiF in Water.
  • Example 7 the solution of Example 7 was prepared by dissolving 200 grams of chromic acid, 1.36 grams of sulfuric acid, and 2.74 grams of fiuosilicic acid in Water and further diluting with water to a volume of one liter. The noted solutions were placed in the cell and electrolyzed at a cell current of 5 amperes for one minute. The panels were then examined and the maximum thickness of bright chromium plated was determined. Results of these experiments are given in Table II wherein thickness plated is in microns. Numerical values for the noted variables were as shown and those values marked with an asterisk were maintained within their respective preferred specific limits.
  • microns ratio of about 40 and a proportion of about 3 were prepared. These baths were adjusted to chromic acid concentrations of 200, 225, and 250 g./l. and were electrolyZed at cathode current densities of 150, 225, 300, 450 and 600 .a.s.d. at a temperature of 71 C. Thus, three of the variables viz. temperature, ratio, and chromic acid concentration were within the specific limits and proportion was within the narrow limits. After one minute of electrolysis, the thickness of bright chromium deposited on a nickel-plated brass panel was measured and expressed in microns. Results of these experiments are presented in Table IV.
  • the novel plated articles of this invention may comprise a basis metal with a bright chromium plate electrodeposited thereon by the process which comprises maintaining a chromium plating bath containing chromic acid and sulfate wherein the vairables chromic acid concentration, ratio, proportion, and temperature are within the limits CrO ..g./l 100-400 Ratio 25 -1 00 Proportion 0-4 Temperature C- 27-94 and wherein at least two of said variables are within the limits CrO g./l 150-250 Ratio 25-70 Proportion 02 Temperature C 60-82 maintaining in said bath an anode and a cathode; and passing an electric current through said anode, said bath, and said cathode at a cathode ccurrent density of at least about 150 amperes per square decimeter, thereby electroplating bright chromium plate on said cathode at a rate of at least about 1.25 microns per minute.
  • novel chromium plated articles which may be produced by the process of this invention may be characterized by their superior smoothness, brightness, hardness and lack of undesirable pores especially when compared to articles plated at very high plating speeds in prior art baths.
  • the process for electroplating bright chromium plate at high plating speeds which comprises maintaining a chromium plating bath containing chromic acid and at least one catalyst anion selected from the group consisting of sulfate, fluoride, complex fluoride and mixtures thereof wherein the variables chromic acid concentration, ratio of chromic acid to the sum of the concentrations of said catalyst anions, proportion of fluoride and complex fluoride to sulfate, and temperature are within the limits CrO g./l -400 Ratio 25-100 Proportion 04 Temperature C 27-94 and wherein at least two of said variables are within the limits CrO g./l -250 Ratio 25-70 Proportion 02 Temperature C 60-82 maintaining in said bath an anode and a cathode; and passing an electric current through said anode, said bath, and said cathode, at a cathode current density of at least about 15 0 amperes per square decimeter, thereby electroplating bright
  • the process for electroplating bright chromium plate at high plating speeds which comprises maintaining a chromium plating bath containing chromic acid and at least one catalyst anion selected from the group consisting of sulfate, fluoride, complex fluoride and mixtures thereof wherein the variables chromic acid concentration, ratio of chromic acid to the sum of the concentrations of said catalyst anions, proportion of fluoride and complex fluoride to sulfate, and temperature are within the limits CrO g./l 100-300 Ratio 25-90 Proportion 03 Temperature C 49-88 and wherein at least two of said variables are within the maintaining in said bath an anode and a cathode; and passing an electric current through said anode, said bath, and said cathode, at a cathode current density of about 150-600 amperes per square decimeter, thereby electroplating bright chromium plate on said cathode at a rate of about 1.25-10 microns per minute.
  • the process for electroplating bright chromium plate at high plating speeds which comprises maintaining a chromium plating bath containing chromic acid and at least one catalyst anion selected from the group consisting of sulfate, fluoride, complex fluoride and mixtures thereof wherein the variables chromic acid concentration, ratio of chromic acid to the sum of the concentrations of said catalyst anions, proportion of fluoride and com- 7 plex fluoride to sulfate, and temperature are Within the limits CrO g./l 100-400 Ratio 25-100 Proportion -4 Temperature C 27-94 and whe-rein at least three of said variables are within the limits CrO g./l 150-250 Ratio 25-70 Proportion 0-2 Temperature C 60-82 maintaining in said bath an anode and a cathode; and passing an electric current through said anode, said bath, and said cathode, at a cathode current density of at least about 150 amperes per square decimeter,
  • the process for electroplating bright chromium plate at high plating speeds which comprises maintaining a chr0- mium plating bath containing chromic acid and at least one catalyst anion selected from the group consisting of sulfate, fluoride, complex fluoride and mixtures thereof wherein the variables chromic acid concentration, ratio of chromic acid to the sum of the concentrations of said catalyst anions, proportion of fluoride and complex fluoride to sulfate, and temperature are with the limits 8 CrO g./l 100-300 Ratio 25-90 Proportion 0-3 Temperature C 49-88 and wherein at least three of said variables are within the limits CrO g./l 150-250 Ratio -60 Proportion 0-1 Temperature C -77 maintaining in said bath an anode and a cathode; and passing an elect-ric current through said anode, said bath, and said cathode, at a cathode current density of about -600 amperes per square decimeter, thereby electropla

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electroplating And Plating Baths Therefor (AREA)
  • Electroplating Methods And Accessories (AREA)
US300107A 1963-08-05 1963-08-05 Ultrahigh-speed chromium electrodeposition Expired - Lifetime US3337430A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
US300107A US3337430A (en) 1963-08-05 1963-08-05 Ultrahigh-speed chromium electrodeposition
GB31366/64A GB1079646A (en) 1963-08-05 1964-08-04 Improvements in or relating to chromium plating
NL6408934A NL6408934A (enrdf_load_stackoverflow) 1963-08-05 1964-08-04
DE1964M0062006 DE1496903B2 (de) 1963-08-05 1964-08-05 Verfahren zur galvanischen glanzverchromung
JP39044781A JPS4927017B1 (enrdf_load_stackoverflow) 1963-08-05 1964-08-05

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US300107A US3337430A (en) 1963-08-05 1963-08-05 Ultrahigh-speed chromium electrodeposition

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JP (1) JPS4927017B1 (enrdf_load_stackoverflow)
DE (1) DE1496903B2 (enrdf_load_stackoverflow)
GB (1) GB1079646A (enrdf_load_stackoverflow)
NL (1) NL6408934A (enrdf_load_stackoverflow)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3421986A (en) * 1964-10-28 1969-01-14 Teves Kg Alfred Method of electroplating a bright adherent chromium coating onto cast-iron
US3498892A (en) * 1966-05-04 1970-03-03 M & T Chemicals Inc Electrodeposition of chromium upon a continuous metal strip
CN103122470A (zh) * 2011-11-17 2013-05-29 符士正 汽车铸铁模具镀液

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5339822U (enrdf_load_stackoverflow) * 1976-09-10 1978-04-06

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1942469A (en) * 1931-10-03 1934-01-09 Timken Axle Co Detroit Chromium plating
US2950234A (en) * 1958-02-26 1960-08-23 Metal & Thermit Corp Chromium plating process and bath
US2952590A (en) * 1959-08-14 1960-09-13 Metal & Thermit Corp Process for chromium plating
US3108933A (en) * 1961-02-28 1963-10-29 M & T Chemicals Inc Process and composition for chromium plating

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1942469A (en) * 1931-10-03 1934-01-09 Timken Axle Co Detroit Chromium plating
US2950234A (en) * 1958-02-26 1960-08-23 Metal & Thermit Corp Chromium plating process and bath
US2952590A (en) * 1959-08-14 1960-09-13 Metal & Thermit Corp Process for chromium plating
US3108933A (en) * 1961-02-28 1963-10-29 M & T Chemicals Inc Process and composition for chromium plating

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3421986A (en) * 1964-10-28 1969-01-14 Teves Kg Alfred Method of electroplating a bright adherent chromium coating onto cast-iron
US3498892A (en) * 1966-05-04 1970-03-03 M & T Chemicals Inc Electrodeposition of chromium upon a continuous metal strip
CN103122470A (zh) * 2011-11-17 2013-05-29 符士正 汽车铸铁模具镀液

Also Published As

Publication number Publication date
JPS4927017B1 (enrdf_load_stackoverflow) 1974-07-13
DE1496903A1 (de) 1969-08-14
NL6408934A (enrdf_load_stackoverflow) 1965-02-08
GB1079646A (en) 1967-08-16
DE1496903B2 (de) 1976-10-21

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