US3552993A - Process for rinsing chromium plated parts - Google Patents

Process for rinsing chromium plated parts Download PDF

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Publication number
US3552993A
US3552993A US831346A US3552993DA US3552993A US 3552993 A US3552993 A US 3552993A US 831346 A US831346 A US 831346A US 3552993D A US3552993D A US 3552993DA US 3552993 A US3552993 A US 3552993A
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United States
Prior art keywords
rinse
rinsing
chromic acid
water
objects
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Expired - Lifetime
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US831346A
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English (en)
Inventor
Harry W Buchanan
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CNA Holdings LLC
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Virginia Chemicals Inc
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Assigned to VIRGINIA CHEMICALS INC., A CORP. OF DE. reassignment VIRGINIA CHEMICALS INC., A CORP. OF DE. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: VIRGINIA CHEMICALS INC., A CORP. OF MAINE
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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
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/48—After-treatment of electroplated surfaces
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D21/00—Processes for servicing or operating cells for electrolytic coating
    • C25D21/08—Rinsing

Definitions

  • the process may be delined as chemically rinsing objects which have been wetted with chromic acid solution, with an additive comprising:
  • a chromic acid reducing agent (b) a buffer to stabilize the agent and (c) a surfactant to insure rinse wetting.
  • Chromium plated objects are particularly susceptible to loss of luster, Water spotting, etc., during rinsing as there is generally a reluctance to use adequate rinse water, because of waste disposal problems.
  • Most known surfactants which facilitate improved rinsing also are attacked by chromic acid and lose effectiveness.
  • various uorocarbon surfactants have been employed in chromic acid plating baths to reduce drag-out, but these are considered too expensive to be used to reduce the surface tension of rinse baths.
  • chromic acid plating solution herein is rinsed from plated objects by contacting them with a dilute aqueous solution, containing sodium hydrosulfite, an alkaline buffer such as sodium carbonate, and preferably a surfactant such as nonionic or anionic wetting or dispersing agent.
  • the plated objects are rinsed without loss of luster, without water spotting, and without producing waste rinse waters contaminated with toxic hexavalent chromium ions.
  • the rinsing processes of the present invention thus permit the use of chromic acid sensitive surfactants as rinse aids, because the rinse water is always kept free of hexavalent chromium ions.
  • the present preferred surfactant inhibits oc formation from the trivalent chromium hydroxide.
  • the rinsing can be accomplished in the presence of a considerable amount of trivalent chromium 3,552,993 Patented Jan. 5, 1971 ICC hydroxide without encountering the dulling effect of a dried-on lm. Noteworthy is the fact that the process and product are useful though lacking in a surfactant, per se, as will be explained herein.
  • the process and product are equally useful in the plating of substrates which are of either metal or plastic, the latter having been prepared with a nickel plate base.
  • the process has its widest utility in the broad reduction of the hexavalent chromium ions in solution from any source whatsoever.
  • the etch bath usually comprises a strong solution of chromic acid and sulfuric acid. Following the initial bath with the acid combination complete rinsing hereby is essential to successful sensitizing with stannous chloride and activating with palladous chloride. In this treatment of plastic objects a combination sodium hydrosulte and sodium carbonate solution is prepared without surfactant.
  • the ligure is a ow sheet, diagrammatically depicting one form of the process employed in the present invention.
  • the preferred method of testing for excess reducing power is a titration of a sample from the rinse tank by a standardized solution of rubine dye.
  • the endpoint for the titration is the appearance of a stable pink color.
  • Water is also added to the chemical rinse tank either continuously or periodically to keep the level of colloidal chromium sesquioxide from building up too high. A low concentration thereof should be maintained in the rinse for optimum effectiveness in obtaining maximum brightness on the plated parts. Too much rinse water not only entails high water costs, but also increases the requirement for the chrome-reducing rinse aid needed to maintain reducing conditions in the rinse.
  • a conventional cold water rinse (Tank IV) may be em- -ployed to rinse away any chromium sesquioxide carried over from chemical rinse (Tank II).
  • a hot rinse in mineral-free water facilitates rapid drying of the plated parts and assures a spotless surface thereon.
  • the rinsing of chrome plated parts herein reduces chromic acid staining and eliminates the problem of disposing of highly dilute waste waters containing the toxic hexavalent chromium ion.
  • the process is thus one of chemical rinsing, in which the undesired contaminant which is to be rinsed away, is immediately converted to a less undesirable substance.
  • chrome-plated parts wetted with chromic acid plating solution may be sequentially contacted (Tank III) with a buffered solution of sodium hydrosulfite at a temperature not exceeding F.
  • the additive hydrosulte solution is a dilute aqueous solution preferably of a strength of about 0.025% comprising: a powder made by mechanically blending these three ingredients:
  • Reduction of the chromic acid (Tank III) is essentially instantaneous, even when the hydrosulite content of the rinse bath is less than ten parts per million. Chromium sesquioxide that is formed is then in a dispersed, colloidal state and rinses from the metal easily (Tank IV). It is preferred though not essential that the rinse water (Tank IV) contain a surfactant which not only acts as a dispersing agent for the sesquioxide but also ensures that the chrome plated parts leave the rinse bath (Tank IV) in a water-break-free state. Now, the surfactant, as indicated, may take one of several nonionic or anionic forms or mixtures thereof.
  • nonionics include the nonylphenol polyethylene glycol ethers, tridecyl polyethylene glycol ethers, and Triton CF-54 (a terminated ethoxylated phenol compound manufactured by the Rohm and Haas Co.)-
  • Suitable anionic surfactants include the disodium salt of dioctylsulfosuccinic acid, sodium lauryl sulfate, and sodium dodecylbenzene sulfonate.
  • a preferred composition for use as a chrome-reducing rinse aid (Tank III) has the following formuation:
  • Triton CF-54 is shown in the above formulation, any of the common nonionic or anionic wetting or dispersing agents would perform the function desired in promoting free rinsing and dispersing the colloidal chromium hydroxide. However, Triton CF-54 was chosen for our work because it was known to have optimum performance as a rinse aid in rinsing chrome plated parts.
  • surfactants would include the nonylphenol polyethylene glycol ethers, tridecyl polyethylene glycol ethers, the dioctyl ester of sodium sulfosuccinic acid, and sodium dodecylbenzene sulfonate.
  • other alkaline buffers may be employed in place of the sodium carbonate such as trisodium phosphate, or sodium tripolyphosphate.
  • the surfactant functions as a rinse aid by assuring good wetting of the chrome plated parts. It has a dispersing action on chromium sesquioxide and also renders the product relatively dust-free, thus reducing handling problems.
  • EXAMPLE I A fty-ve gallon, unheated chemical rinse was installed in a chrome plating line between the vcustomary saveall and first cold water rinse. From time to time, several ounces of a chrome-reducing rinse were added to the chemical rinse tank to maintain the rinse in a reducing condition. The formulation for the additive was 66% sodium hydrosulfite, 33% sodium carbonate, and 1% Triton CF-54. As plated parts from the saveall were rinsed iu the chemical rinse tank, a green color initially developed, due to the dispersed chromium sesquioxide. Following a subsequent cold water rinse, no evidence of any dulling film developed on any of the plated parts on continued operation.
  • EXAMPLE II A fifty-five gallon chemical rinse was operated at a temperature of 150-160 F. using the chrome-reducing rinse aid composition as in Example I. Chromium sesquioxide, formed from added chromic acid, at first appeared to -be colloidal but soon iiocculated to large green floc clumps. The floc was not readily removable by settling because of a very slow settling rate and the voluminous nature of the iioc. The lioc could be readily removed however, by circulating the rinse water through a lter.
  • Example IV The composition described in Example I was again used to clean up a quantity of chromic acid plating solution that was accidentally spilled on the oor. The reduction of the hexavalent chromium was immediate, thus preventing any of the toxic material from entering the sewer.
  • an improved method comprising the steps of (A) initially chrome plating the object by exposure thereof to a chromic acid plating solution,
  • (B3) a non-cationic surfactant to ensure rinse setting of the object, the rinsing being conducted at such a rate as to ensure an excess of reducing effectiveness.
  • an improved method comprising the steps of (A) initially chrome plating the object by exposure thereof to a chromic acid plating solution, sequentially (B) chemically rinsing the initially rinsed plated object with an aqueous solution containing an additive comprising:
  • (B3) a non-ionic wetting agent surfactant to ensure rinse wetting of the object, the rinsing being conducted at such a rate as to ensure an excess of reducing eifectiveness.
  • aqueous solution is a dilute solution of a formulated mixture comprising the following in percentage by weight:
  • aqueous solution is a dilute solution of a formulated mixture comprising the following in percentages by weight:

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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)
  • Chemically Coating (AREA)
  • Chemical Treatment Of Metals (AREA)
US831346A 1969-06-09 1969-06-09 Process for rinsing chromium plated parts Expired - Lifetime US3552993A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US83134669A 1969-06-09 1969-06-09

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US (1) US3552993A (de)
DE (1) DE2028366B2 (de)
FR (1) FR2050991A5 (de)
GB (1) GB1286718A (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3904491A (en) * 1973-10-12 1975-09-09 Nat Steel Corp Controlling electrolyte concentration in electrolytic and rinsing treatment of chrome plated steel strip
CN100371504C (zh) * 2005-02-20 2008-02-27 重庆建设摩托车股份有限公司 消声器镀铬后铬酐的清除方法
CN110453234A (zh) * 2019-09-03 2019-11-15 深圳市文壹科技有限公司 一种用于制作软包电池负极极耳所需镍带的表面处理工艺
CN110468397A (zh) * 2019-09-03 2019-11-19 深圳市文壹科技有限公司 一种用于制作软包动力电池所需镀镍铜带的表面处理工艺
CN110565103A (zh) * 2019-09-03 2019-12-13 深圳市文壹科技有限公司 一种用于制作软包动力电池正极极耳所需铝带的表面处理工艺

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3904491A (en) * 1973-10-12 1975-09-09 Nat Steel Corp Controlling electrolyte concentration in electrolytic and rinsing treatment of chrome plated steel strip
CN100371504C (zh) * 2005-02-20 2008-02-27 重庆建设摩托车股份有限公司 消声器镀铬后铬酐的清除方法
CN110453234A (zh) * 2019-09-03 2019-11-15 深圳市文壹科技有限公司 一种用于制作软包电池负极极耳所需镍带的表面处理工艺
CN110468397A (zh) * 2019-09-03 2019-11-19 深圳市文壹科技有限公司 一种用于制作软包动力电池所需镀镍铜带的表面处理工艺
CN110565103A (zh) * 2019-09-03 2019-12-13 深圳市文壹科技有限公司 一种用于制作软包动力电池正极极耳所需铝带的表面处理工艺

Also Published As

Publication number Publication date
FR2050991A5 (de) 1971-04-02
DE2028366B2 (de) 1973-02-01
GB1286718A (en) 1972-08-23
DE2028366A1 (de) 1971-02-11

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Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:VIRGINIA CHEMICALS INC., A CORP. OF MAINE;REEL/FRAME:003938/0131