US2787588A - Chromium plating - Google Patents

Chromium plating Download PDF

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Publication number
US2787588A
US2787588A US449378A US44937854A US2787588A US 2787588 A US2787588 A US 2787588A US 449378 A US449378 A US 449378A US 44937854 A US44937854 A US 44937854A US 2787588 A US2787588 A US 2787588A
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US
United States
Prior art keywords
bath
alkali metal
sulfate
concentration
silicofluoride
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 - Lifetime
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US449378A
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English (en)
Inventor
Jesse E Stareck
Dow Ronald
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Primerica Inc
Original Assignee
Metal and Thermit Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Metal and Thermit Corp filed Critical Metal and Thermit Corp
Priority to US449378A priority Critical patent/US2787588A/en
Priority to GB22186/55A priority patent/GB812337A/en
Priority to DEU3457A priority patent/DE1044550B/de
Priority to FR1129375D priority patent/FR1129375A/fr
Application granted granted Critical
Publication of US2787588A publication Critical patent/US2787588A/en
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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

  • the present invention has tl e same purpose aslthe said copending t tpplic ation and utilizes similar, means for accomplishingthe purpose except that only aportion of. the catalyst acidrgdical content of, the bath solution is controlled by non-catalytic suppressor compounds.
  • the present methodthebath solution comprises chromic acid, two catalyst-supplying compounds, namely, strontium sulfate and an alkali; metal silicofluoride, each having a limited solubility in the chromic acid bath, and a soluble non? catalytic alkali metal compound.v
  • the alkali metal Ofthe non-catalytic compound is the same as that; of, the silicofiuoride compound and. is selected-fromthe. group.
  • the non-catalyticcompound has the effect of controlling. the, concentratiomof. the dissolved silicofluoride radical in, theibathby .decreas; ing the solubilitvof the; alkali metal silicofluoride; V
  • concentrations of the dissolved sulfate and silicofluoride radicals are self-regulated, but -the sulfateconcentration is not controlled by a non-catalyticcompound.
  • Specific non-catalytic compounds .are potassium or sodium..hydroxid e, potassium or sodium bichromate, potassium or sodium carbonate, and potassium or sodium chromate; ,Th concentration of the .chromic.
  • The-arnount of the strontium sulfate and the alkali metal silicofluoride is, in each case, suflicient to saturate the bath with dissolved sulfate and silicofluorideand to provide anin; soluble residueiof each ,saltin, the bath.
  • the soluble noncatalytic alkali metallcom pound is pres llt in an amount sufficient to adjust.
  • theplate that is deposited is .crac k-free and has theother advantages described hereinafter; At catalyst eoncentrationsthat.lieabovethe curve DCQ -the plate is cracked, and at catalystconcentrationsbelow-the curve AB, the.- plate .is nodular and-unsuitable.
  • the abovedescribed variation of tIie-chroinic acid with the sum of the sulfate. and silicofluoride may; also be shown" by Table. l,v .which also. shows -how the sulfate and silicofiuoride concentrations may individually vary:
  • the amount of the. non-cata1ytic.. alkali metal compo 11d is such ,asfto suppressgthe concentration of the silicofluoride in solution in the bath fromthe-unsuppressed saturation concentration of the latter to a lower concentration such that the sum of the dissolved sulfate (504:) :andsilicofluoride (SiFzjisizQ to 8, 5 gIAl.
  • The. preferred concentration of dissolved sulfate mavvary from 1.8 to 5.0 g./l.
  • A;more preferredrange of CrO concentration isjQQ to.,700 g./-l., with the dissolved sulfate varying'ifronrlfi to 3.-5- g. /l:, the .dissolvedsilicoflnoride varying'LfromZO toil) g./l.,',.and the sum of the two catalysts varying from 3.5.;10 6.5 gI/L: r f
  • Thev chromic acid: content may be supplied by; adding chromit; acid -.as such.to the bath, although a portion mayv be supplied by the CrOs content of non-catalytic compounds like potassium on. sodium bichrornateand potassiuino r sodium chromate....lt will be-und-erstood that in referring to the .bathchromici-acid content-it is-intended to. include, .unless specified. otherwise, I the CrOa added-:per seia nd an yl.CrOg-addedinihe form of one of the foregoing non-catalyticcompoundsq-fi, I 3
  • the bath is operated at a minimum temperature of 140 F., it having been found that below this temperature the plate that is produced is cracked.
  • the upper temperature may extend to the boiling point of the bath but preferably is about 180 F.
  • a preferred temperature range is 145 to 160 F.
  • concentrations of dissolved ClOs, sulfate and silicofluoride should be higher, and higher current densities are used.
  • the crack-free quality of the chromium plate produced by the present method is not only determinable visually but also by means of other tests, as described in the said copending application.
  • the crack-free plate of the invention is also characterized by having a hardness of about 425 to about 825, usually 550 to 700, Knoop.
  • the plate is relatively soft and ductile as compared with conventional chromium plate. It has a smooth texture, a satiny finish, and a dull, matte, white color. It is easy to polish or buff.
  • Example 1 From a mixture of 410 parts of chromic acid, 284
  • Example 3 A mixture of 446 parts of chromic acid, 80 parts of potassium dichromate, parts of potassium of silica fluoride, and 10 parts of strontium sulfate, all parts by weight, were dissolved in water to form a solution containing 500 g./ 1. of dissolved CrOs, 1.8 g./ 1. of sulfate, and 2.0 g./ 1. of silicotluoride. A steel mandrel of conventional size was plated in this solution at 150 F. and 3 a. s. i. for 1 hour, a smooth, dull white crack-free plate being produced.
  • weight percentages of the ingredients of the solid mixture for making up the bath solution can also be expressed as parts by weight.
  • Deposits of varying thicknesses may be plated by the present method, ranging for example from a thickness just sufficient to cover the pores of the basis metal to any practical desired thicker deposit for which a demand may exist.
  • the invention is useful for articles made of any of a variety of basis metals, such as plain carbon steels, alloy steels including stainless steel, iron, cast iron, copper and copper alloys, nickel and nickel alloys, zinc and zinc alloys, aluminum and aluminum alloys, tin and tin alloys, lead and lead alloys, etc.
  • basis metal may be any metal, or an undercoat on a metal, that can be chromium plated.
  • a method of electrodepositing crack-free,.chromium plate on a metal article which comprises essentially: pass A steel rod 3" ing current in the range of 0.5 to 8 amperes per square inch from an anode to said article as a cathode immersed in an aqueous chromium plating bath at a temperature of F. to the boiling point of the bath, said bath comprising essentially 300 to 900 g./l.
  • a method according to claim 1 in which the metal article that is chromium plated is an article of plain carbon steel.
  • alkali metal silicofluoride is potassium silicofluoride and the non-catalytic alkali metal compound is a potassium compound.
  • alkali metal silicofluoride is sodium silicofiuoride and the noncatalytic alkali metal compound is a sodium compound.
  • a method of electrodepositing crack-free, chromium plate on a metal article which comprises essentially: passing current in the range of 1 to 3 amperes per square inch from an anode to said article as a cathode immersed in an aqueous chromium plating bath at a temperature of to F., said bath comprising essentially 400 to 900 g./ 1.
  • strontium sulfate and an alkali metal silicofluoride each in an amount sufficient to saturate said bath and to provide therein an undissolved residue of strontium sulfate and alkali metal silicofluoride, respectively, and a soluble non-catalytic alkali metal compound in an amount sufficient to suppress the concentration of the alkali metal silicofluoride in solution in said bath so that the sum of the dissolved sulfate and silicofiuoride is in the range'of 3.0 to 8.5 g./l., said alkali metal of the noncatalytic compound being the same as that of the alkali metal silicofiuoride and being selected from the group consisting of sodium and potassium, said bath being free of compounds acting to suppress the concentration of dissolved sulfate, and said sum of dissolved sulfate and silicofluoride varying with the CrOs concentration in the manner defined by the area JKLM of the graph shown in the accompanying drawing.
  • An improved method of producing a cororsion re sistant chromium plated metal article comprising plating the unplated article, in a single plating operation, in an aqueous bath comprising essentially 300 to 900 g./l. CrOs, strontium sulfate and an alkali metal silicofiuoride each in an amount sufficient to saturate said bath and to provide therein an undissolved residue of strontium sulfate and alkali metal silicofiuoride, respectively, and a soluble non-catalytic alkali metal compound in an amount suflicient to suppress the concentration of the alkali metal silicofiuoride in solution in said bath from the unsuppressed saturation concentration of the latter compound to a lower concentration equivalent to 1.0 to 9.0 g./ 1.
  • concentration of dissolved sulfate 504 being from 1.5 to 5.5 g./ 1.
  • the sum of said dissolved sulfate and silicofiuoride being in the range of 2.5 to 10.5 g./ 1.
  • said bath being free of compounds acting to suppress the concentration of dissolved sulfate, said sum of dissolved sulfate and silicofluoride varying with the C103 concentration in the manner defined by the area ABCD of the graph shown in the accompanying drawing, the alkali metal of the non-catalytic compound and of the alkali metal silicofluoride being the same and being selected from the class consisting of potassium and sodium; performing the plating at a bath tem perature of 140 to 180 F. and a current density of 0.5

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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)
  • Catalysts (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
US449378A 1954-08-12 1954-08-12 Chromium plating Expired - Lifetime US2787588A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US449378A US2787588A (en) 1954-08-12 1954-08-12 Chromium plating
GB22186/55A GB812337A (en) 1954-08-12 1955-08-02 Electrodeposition of chromium plate
DEU3457A DE1044550B (de) 1954-08-12 1955-08-08 Verfahren zur elektrolytischen Herstellung rissfreier Chromueberzuege auf Metallgegenstaenden
FR1129375D FR1129375A (fr) 1954-08-12 1955-08-11 Procédé de chromage électrolytique

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US449378A US2787588A (en) 1954-08-12 1954-08-12 Chromium plating

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US2787588A true US2787588A (en) 1957-04-02

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US449378A Expired - Lifetime US2787588A (en) 1954-08-12 1954-08-12 Chromium plating

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US (1) US2787588A (fr)
DE (1) DE1044550B (fr)
FR (1) FR1129375A (fr)
GB (1) GB812337A (fr)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2950234A (en) * 1958-02-26 1960-08-23 Metal & Thermit Corp Chromium plating process and bath
US3259560A (en) * 1961-07-26 1966-07-05 Nat Res Dev Process for the electrolytic production of cromium of a high degree of purity
US3303114A (en) * 1964-01-10 1967-02-07 Udylite Corp Chromium plating
US3303113A (en) * 1963-10-18 1967-02-07 Udylite Corp Chromium plating
US3334033A (en) * 1964-09-11 1967-08-01 Udylite Corp Chromium plating
FR2171112A1 (fr) * 1972-02-10 1973-09-21 Norton Co

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2916424A (en) * 1957-11-07 1959-12-08 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

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2640022A (en) * 1950-11-07 1953-05-26 United Chromium Inc Composition, bath, and process for chromium plating
US2640021A (en) * 1949-11-23 1953-05-26 United Chromium Inc Composition, bath, and process for chromium plating
US2686756A (en) * 1953-05-20 1954-08-17 United Chromium Inc Chromium plating

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2469015A (en) * 1943-02-20 1949-05-03 United Chromium Inc Method and compositions for producing surface conversion coatings on zinc
US2499231A (en) * 1944-08-25 1950-02-28 United Chromium Inc Method of producing surface conversion coatings on zinc

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2640021A (en) * 1949-11-23 1953-05-26 United Chromium Inc Composition, bath, and process for chromium plating
US2640022A (en) * 1950-11-07 1953-05-26 United Chromium Inc Composition, bath, and process for chromium plating
US2686756A (en) * 1953-05-20 1954-08-17 United Chromium Inc Chromium plating

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2950234A (en) * 1958-02-26 1960-08-23 Metal & Thermit Corp Chromium plating process and bath
US3259560A (en) * 1961-07-26 1966-07-05 Nat Res Dev Process for the electrolytic production of cromium of a high degree of purity
US3303113A (en) * 1963-10-18 1967-02-07 Udylite Corp Chromium plating
US3303114A (en) * 1964-01-10 1967-02-07 Udylite Corp Chromium plating
US3334033A (en) * 1964-09-11 1967-08-01 Udylite Corp Chromium plating
FR2171112A1 (fr) * 1972-02-10 1973-09-21 Norton Co

Also Published As

Publication number Publication date
FR1129375A (fr) 1957-01-21
DE1044550B (de) 1958-11-20
GB812337A (en) 1959-04-22

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