Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D235/00—Heterocyclic compounds containing 1,3-diazole or hydrogenated 1,3-diazole rings, condensed with other rings
  • C07D235/02—Heterocyclic compounds containing 1,3-diazole or hydrogenated 1,3-diazole rings, condensed with other rings condensed with carbocyclic rings or ring systems
  • C07D235/04—Benzimidazoles; Hydrogenated benzimidazoles
  • C07D235/06—Benzimidazoles; Hydrogenated benzimidazoles with only hydrogen atoms, hydrocarbon or substituted hydrocarbon radicals, directly attached in position 2
  • C07D235/08—Radicals containing only hydrogen and carbon atoms
• • 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
  • C25D3/10—Electroplating: Baths therefor from solutions of chromium characterised by the organic bath constituents used

Definitions

• This invention relates to chromium plating. More particularly it relates to a novel technique for suppressing the evoluton of fumes from chromium plating baths.
• chromium plating may be effected from baths which contain chromic acid and sulfate (typically introduced as sulfuric acid) together with other ingredients or additives including those which may control or regulate the plating characteristics of thebath.
• Typical of such regulating additives may be strontium sulfate and potassium silicofluoride with or without additions of excess strontium ion (introduced as SrCO SrCrO etc.) or excess potassium ion (introduced as K2CIO4, K Cr O etc.) which may make the bath a high speed bath which is self-regulating with respect to catalyst anion concentrations.
• chromium plating may be effected in a bath containing chromic acid and sulfate wherein substaintial quantities of gas may be liberated from the electrodes by the process which comprises maintaining a chromium plating bath containing chromic acid and sulfate, maintaining therein a relatively small, antimisting amount of a sulfonated 2-alkylbenzimidazole, and plating chromium onto a cathode in said bath.
• the novel composition of this invention which is characterized by its ability to develop and maintain over an extended period of time an optimum thickness of foam, may comprise an aqueous acid chromium plating solution and, as antimisting agent, a relatively small anti-misting amount of a sulfonated 2-alkylbenzimidazole.
• chromium plating baths with which this invention may be employed may commonly have the following illustrative compositions:
• l 1 E.g. from sulfuric acid.
• novel fume-suppressant or anti-misting agent of this invention may be a compound which may typically have the structure wherein Ar is selected from the group consisting of phenyl and naphthyl rings, said ring being incorporated into the imidazole structure through vicinal carbon atoms of said ring (i.e.
• M is a cation selected from the group consisting of hydrogen, ammonium and metals
• R is a non-aromatic hydrocarbon radical containing at least 3 carbon atoms
• R is selected from the group consisting of hydrogen, alkyl, aryl, aralkyl, omegasulfonated alkyl, sulfonated aryl, and sulfonated aralkyl
• R" is selected from the group consisting of hydrogen, alkyl and aralkyl
• Y is a water-soluble anion
• a is 01.
• the group Ar may be phenyl or naphthyl, and preferably it may be phenyl.
• the cation M may be a metal (including hydrogen and ammonium).
• M may be selected from the group consisting of hydrogen, ammonium, sodium, potassium, lithium, trivalent chromium, calcium, strontium, copper.
• M may be ammonium or an alkali metal e.g. sodium, potassium and lithium. 1
• the group R may be a non-aromatic hydrocarbon containing at least 3 carbon atoms.
• R may be selected from the group consisting of alkyl, cycloalkyl, alkenyl, and cycloalkenyl radicals.
• R may contain' at least 8, say 818 carbon atoms.
• Preferred R groups may include n-octyl, isooctyl, nonyl, decyl, undecyl, tridecyl, pentadecyl, heptadecyl, octadecyl, 4- ethylcyclohexyl, octenyl, nonenyl, undecenyl, tridecenyl, pentadecenyl, heptadecenyl, 4-amylcyclohexenyl, etc.
• the group R may be hydrogen, alkyl, aryl, aralkyl, omega-sulfonated alkyl, sulfonated aryl or sulfonated aralkyl.
• R may be omega-sulfonated alkyl, sulfonated aryl or sulfonated aralkyl and most preferably R may be selected from the group consisting of omegasulfonated lower alkyl (i.e. an alkyl containing less than about 6 carbon atoms), sulfonated phenyl and sulfonated benzyl.
• the sulfonate group contained in the R group may typically be of the form MO S wherein M is as defined supra and preferably wherein M is ammonium or alkali metal, e.g. sodium, potassium or lithium.
• R may be hydrogen, alkyl or aralkyl.
• R may be selected from the group consisting of hydrogen, lower alkyl (i.e. an alkyl containing less than about 6 carbon atoms) and benzyl. Most preferably, R" may be benzyl.
• the group Y may be a solubilizing anion, typically a water-soluble anion.
• Y may be selected from the group consisting of bromide, iodide, sulfate, acetate, methosulfate, ethosulfate, citrate, and perchlorate.
• the sulfonated 2-alkylbenzimidazoles which may be present in the novel compositions of this invention may preferably contain a quaternary nitrogen atom.
• a may be 1 and the compound may be a quaternized sulfonated 2-alkylbenzimidazole.
• the compound as added may contain no quaternized nitrogen atom.
• Examples of illustrative sulfonated 2-alkylimidazole compounds which may be used in the novel fume-suppressant compositions of this invention may include: (A) sodium 2-n-heptadecyl-3-sulfophenylbenzimidazole sulfonate (B) sodium 2-n-heptadecyl-3-sulfobenzylbenzimidazole sulfonate (C) potassium 2-n-octyl-3-omega-sulfo-n-butylbenzimidazole sulfonate (D) sodium 1-benzyl-2-n-undecyl-3-sulfobenzylsulfobenzimidazolium bromide (E) potassium 1-methyl-2-pentadecyl-3-sulfophenylf sulfobenzimidazolium acetate (F) sodium 1-ethyl-2-nonyl-3-omega-sulfo
• novel fume suppressants may typically be added to the bath as a solid or in aqueous solution. Typical solutions may contain about 120%, say 10%, by weight of the novel fume-suppressant compound.
• the dry material may also be compressed, i.e., pelletized, preferably together with a release agent, say sodium bicarbonate. Mixtures of the noted sulfonated Z-a'lkylbenzimidaz oles may also be employed.
• this blanket should be stable and of substantial, yet not too great, thickness, since too thick a foam blanket could be dangerous because of the large amount of entrapped oxygen and hydrogen, and consequent implosion hazard.
• the geometry of the plating system affects the desired concentration of additive as it will affect the thickness of the foam blanket for a given volume of bath.
• the 'bath may preferably contain less than 0.2 g./l., say about 0.001 g./l. to 0.2 g./l. Larger amounts may be used for intermittent operation but for continuous electrolysis it is better to use only 0.2 g./l. or less, as otherwise the foam blanket may foam to an inconvenient thickness.
• the novel fume-suppressant composition may be present in chromium plating baths in the amount of about 0.001 to 0.2 g./l. of bath.
• the composition may be present in the amount of 0.002 to 0.05, say 0.01 g./l. of bath.
• the anti-misting properties of the novel composition of this invention may endure over an extended period of time even when a very low concentration of the fume-suppressant is used. Because of the outstanding stability and high degree of effectiveness of these fume-suppressants, contamination of the bath by decomposition products is minimized.
• the thickness of the foam blanket was measured from time to time with the following results:
• EXAMPLE 2 Four liters of chromium plating solution containing 250 g./l. CrO and 2.5 g./l. 50.; was placed in a battery jar. The solution depth was 21 cm. and the surface area was about 195 sq. cm. The solution was heated to 49 0, two lead anodes and a brass cathode were positioned therein, and a cell current of 5 amperes Was applied. A vigorous release of spray was observed at the electrodes.
• EXAMPLE 3 In a manner similar to that described in Example 2, sodium 2-n-heptadecyl-3-omega-sulfo-n-propylbenzimidazole sulfonate was tested as a spray suppressant. Addition of 0.1 g./l. of this material to a chromium plating bath gave complete spray suppression and a foam blanket of about 2.5 cm. after 6 hours of electrolysis.
• novel agents of this invention are characterized by their surprisingly high durability and effectiveness.
• compositions of this invention may produce less sulfate build-up in a commercial bath than fume-suppressants previously used. Sulfate ion is produced when the fumesuppressant breaks down in the plating bath. Since the compositions of this invention may be effective for several times as long as previously used agents, they need not be added as frequently, and sulfate build-up may be thereby reduced.
• a novel bath for the electrodeposition of chromium comprising an aqueous acid chromium plating solution and, as an anti-misting agent, 0.00l-0.2 g./l. of a sulfonated 2-alkyl benzimidazole.
• a novel bath for the electrodeposition of chromium comprising an aqueous acid chromium plating solution and, as an anti-misting agent, 0.0010.2 g./l. of a compound having the formula wherein Ar is selected from the group consisting of phenyl and naphthyl rings, said ring being incorporated into the imidazole structure through vicinal carbon atoms of said ring; M is a cation selected from the group consisting of hydrogen, ammonium and metals; R is a non-aromatic hydrocarbon containing 3-18 carbon atoms; R is selected from the group consisting of omega-sulfonated lower alkyl, sulfonated phenyl and sulfonated benzyl; R is selected from the group consisting of hydrogen, lower alkyl and benzyl; Y is a Water-soluble anion; and a is 0-1.
• a novel bath for the electrodeposition of chromium comprising an aqueous acid chromium plating solution and, as an anti-misting agent, 0.002-0.05 g./l. of a compound having the formula I I R wherein Ar is selected from the group consisting of phenyl and naphthyl rings, said ring being incorporated into the imidazole structure through vicinal carbon atoms of said ring; M is a cation selected from the group consisting of hydrogen, ammonium and metals; R is a non-aromatic hydrocarbon containing 318 carbon atoms; R is selected from the group consisting of omega-sulfonated lower alkyl, sulfonated phenyl and sulfonated benzyl; R" is selected from the group consisting of hydrogen, lower alkyl and benzyl; Y is a water-soluble anion; and a is 0-1.
• a novel bath as claimed in claim 10 wherein the compound is sodium 2-n-heptadecyl-3-sulfopheny1benzimidazole sulfonate.
• a novel bath as claimed in claim 10 wherein the compound is sodium Z-n-heptadecyl-3-sulfobenzylbenzimidazole sulfonate.
• a novel bath as claimed in claim 10 wherein the compound is sodium Z-n-heptadecyl 3 iomega-sulfo-npropylbenzimidazole sulfonate.

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

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  • GB GB1050223D patent/GB1050223A/en active Active
• 1963
  • 1963-09-24 US US311223A patent/US3341434A/en not_active Expired - Lifetime
• 1964
  • 1964-09-24 CH CH1238864A patent/CH471233A/de not_active IP Right Cessation
  • 1964-09-24 NL NL646411161A patent/NL148113B/xx not_active IP Right Cessation
  • 1964-09-24 DE DE1496905A patent/DE1496905C3/de not_active Expired

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