Classifications

• • 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
  • C25D3/22—Electroplating: Baths therefor from solutions of zinc

Definitions

• ABSTRACT A non-poisonous zinc plating bath comprising a fundamental plating composition including zinc salt and ammonium salt with or without hydroxy carboxylic acid; a sulfate compound or compounds having the general formula A.B -4CH CH Oi- -.mSO M; an alkylnaphthylketon compound or compounds having the general formula R COR1;
• This invention relates to novel and improved nonpoisonous zinc plating baths which contain no cyanide therein and which can effectively eliminate occurrence of harmful environmental contamination even when the waste liquids from the baths are discarded out of the system.
• One typical prior art zinc plating bath for use in zincplating the surfaces of various base metals has the composition which principally comprises 80 g/l of sodium hydroxide, 35 g/l of Zn and lOO g/l of sodium cyanide and the waste liquid from the plating bath includes cyan-containing substances in a substantially high concentration. Therefore, when the waste liquid, is discarded out of the system into a river or sea, for example, the liquid will seriously contaminate the water in the river or sea.
• Another object of the present invention is to provide a non-poisonous zinc plating bath which has a wide range of brilliance-imparting current density available, can be effectively applicable to barrel plating, is excellent in performance and will not cause harmful environmental contamination.
• the non-poisonous zinc plating bath of the present invention generally comprises (a) a conventional zinc plating composition comprising zinc salts and ammonium salt with or without hydroxy carboxylic acid; (b) a sulfate compound or compounds of polyether having the below-mentioned general formula:
• A is hydrogen, CI'IHQ" l (n is an integral within the range of 4 20), alkylphenylene, residue after removal of the hydroxy group from molecules of sorbitol or mannitol or residue of alkylpolyamine
• B is a bridge selected from the group comprising -COO, -NH, S', O, (OCH CH CH2O)7 and CONH
• M is hydrogen, ammonium or a metal selected from the group'comprising, sodium
• R is a group selected from the group comprising hydrogen, halogen, alkyl, alkoxyl, aryl, amino, nitro, hydroxyl, carboxyl, sulfo,- sulfomoyl, substituted sulfomoyl, hydroxycarboxyalkyl, carboxy vinylene, carboxy phenylene, carboxyalkyi, phenylvinylene and mercapto.
• Zinc salts, ammonium salts and hydroxy carboxylic acids to be blended with the other components of the zinc plating baths of the invention may be those usually employed in the conventional zinc plating baths compositions and the zinc salts useful in the baths of the invention include zinc chloride, zinc sulfate and zinc sulfaminate. These zinc salts can be employed in amounts tag in .19, t 2QQs/Llh9a91m msa useful in the baths of the invention include ammonium chloride, ammonium sulfate and ammonium acetate and these ammonium salts can be employed in amounts ranging from 20 to 350 g/l with satisfactory results.
• hydroxy carboxylic acids useful in the baths of the invention include maleic acid, citric acid, gluconic acid, tartaic acid and lactic acid and these hydroxy carboxylic acids can be optionally employed in amounts ranging from 1 to 100 g/l.
• any one of the above-mentioned zinc salts and any one of the above-mentioned ammonium salts are blended together or alternatively, anyone of the abovementioned hydroxy carboxylic acids is further added to the blend. Thereafter, the resulting mixture is added thereto the compounds represented by the general formulas I (2) and (3), respectively, thereto to prepare non-poisonous zinc plating baths.
• the mixture of zinc and ammonium salts with or without hydroxy carboxylic acid will be referred to as the fundamental bath composition hereinafter.
• the nitrogen-containing heterocyclic ring compound or compounds substituted with carboxyl group having the general formula (3) have buffering action upon the pH of the plating bath thereby to facilitate the pH control of the plating bath.
• the nitrogen-containing heterocyclic ring carboxylic acid compound or compounds extend the current density range of the plating bath available to impart brilliance to the surfaces of a base metal to be plated and in other words, the compound or compounds serve to reduce the necessary brillianceimparting currency density from a higher value portion thereby to substantially improve the brilliance and covering power of deposit metal on the base metal even when the bath is employed for barrel plating which must be usually carried out at a relatively low current density.
• Such a zinc plating bath cannot be employed forrack and barrel platings which require the brillianceimparting current density range of 0.5- A/dm and 0.1-3 A/dm respectively.
• the above-mentioned control bath was added thereto 3 g/l of quinaldinic acid which is a typical nitrogencontaining heterocyclic ring compound substituted base metal, it was surprisingly found that the brillianceimparting current density range of the bath containing the carboxylic acid compound was extended to the range of 0.1 2O A/dm and could be suitably employed for plating articles having complicate contours and shapes with satisfactory results. It was also found that the bath with the addition of the carboxylic acid compound could be satisfactorily employed for barrel plating which would generally require a relatively low current density.
• the amount range of the additive carboxylic acid compound or compounds is preferably within the range of 0.1 15 g/l.
• the pH of the zinc plating bath of the invention is preferably maintained within the range of 3.0 10. The reason is that when the pH is below 3.0, the plated product will be readily subjected to corrosion and the additive carboxylic acid compound or compounds will salt out and on the other hand, when the pH is over 10, the ammonia contained in the bath is allowed to disperse by evaporation. Therefore, the pH of the bath is preferably maintained within the range of 3 10.
• the temperature of the plating bath is preferably maintained within the range of l0-50C.
• plating operations employing baths of the nonpoisonous zinc plating compositions of the invention can be performed while the baths being maintained static, better results will be obtained when the baths are air-agitated or by the adoption of the so-called cathode rocker system.
• Typical nitrogen-containing heterocyclic ring compounds substituted with carboxyl group which are suitably employed in the present invention will be given hereinbelow, and in connection with this it is to be understood that they can be employed either in their simple forms or in the forms of various mixtures thereof.
• the sulfate compound or compounds of polyether when employed in conjunction with the fundamental bath composition serve to suitably control the electrodeposition of zinc and this is considered due to the fact that a thin colloidal film is probably formed in the cathode because of the structure of +CH CH O #present in the molecules of the polyether compound or compounds.
• the sulfate compound or compounds of polyether may serve to control extra-ordinary deposition of zinc at high current densities thereby to prevent the formation of dendrite.
• the suitable amount of the sulfate compound or compounds of polyether to be added to the baths of the invention when the sulfate compound or compounds are employed in amounts less than 0.1 g/l, the abovementioned operative effects cannot befully realized and on the other hand, when the amount is over 30 g/l, the obtained deposit metal will be brittleand will be readily subjected to salting-out. Therefore, the sulfate compound or compounds of polyether are preferably employed in amounts from 0.1 to 30 g/l.
• Typical sulfate compounds of polyether to be employed in the baths of the present invention will be shown hereinbelow by their chemical formulas. These sulfate compounds may be employed either in their simple forms or in the forms of mixtures thereof with h P ti mpsr t an as. .4
• zinc plating baths were prepared by adding acetophenone in the amount range from 0.1 to 20 g/l to the fundamental composition including a sulfate compound or compounds of polyether in the abovementioned amount range and a heterocyclic ring compound or compounds substituted with carboxyl group in the above-mentioned amount range as taught in the above-mentioned French patent, but the brillianceimparting current density range of these baths was narrow such as being 0.5 2 A/dm whereas in the others of the experiments, plating baths were prepared by adding an alkylnaphthylketon compound or compounds in the above-mentioned amount range to the fundamental composition including the compound or compounds of the general formula (1) and the compound or compounds of the general formula (3) without the use of acetophenone and the brilliancem122tt ns q nt sistt it nsz .that?
• bathin 9 wider such as being 0.1 to 20 A/dm and bright plated products were obtained over.
• an alkylnaphthylketon compound or compounds to be added to the plating baths of the invention when the 8 l2.
• 1-hydroxy-4-chl6r6 2 a etonaphihbri 13.
• 1-carboxy-5-acetonaphthone 14.
• 5-chl0ro-2-acet0naphth0ne 20 respectively to prepare the zinc plating baths.
• Test 2 5-methyl-2-acet0naphth ne pieces were zinc-plated using the thus prepared baths 3. S-amino-l-acetonaphthone under the conditions such as the temperature of 30C, 4. 1,5-diacetonaphthone the current density of 3 A/dm and pH of 5.0 while agi- 5. acetonaphthone (l or 2) tating the baths with air.
• the zinc-plated test pieces 6. 2-phenylnaphthylketone were measured or observed in accordance with the 7.
• a zinc plating bath was prepared by adding 10 g/l of cgH g SO Na as a Sulfate Compound of polyether, 3 g/l of 2-methyl-3- carboxyquinoline as a carboxylic acid compound of nitrogen-containing heterocyclic ring and 0.6 g/l of 5-chloro-2-acetylnaphton as an alkylnaphthylketon compound to the fundamental composition comprising 120 g/l of zinc chloride and 190 g/l of ammonium chloride and a zinc plating operation was conducted using the bath under the conditions such as the temperature of 25C, the pH of 5.0 and the current density of 5 A/dm" for minutes. The obtained deposit metal had a high brilliance.
• a zinc plating bath was prepared by adding 8 g/l of EXAMPLE 3
• a zinc plating bath was prepared by adding 10 g/l of C,,H, +OCH CH CH O)-(CH CH OM SO Na, 3 g/l of nicotinic acid and 2.5 g/l of B-sulfo-Z-acetylnaphton to the fundamental plating composition comprising 200 g/l of zinc sulfate, 30 g/l of ammonium chloride and g/l of sodium salt of maleic acid and a zinc plating operation was conducted using the bath under the conditions such as the temperature of C, the pH of 1,5
• the obtained deposit metal had a high brilliance.
• a zinc plating bath was prepared by adding l5 g/l of carboxyisoquinoline and 0.9 g/l of S-methyl-B- acetonaphton to the fundamental composition comprising 40 g/l of zinc chloride and 230 g/l of ammonium chloride and a zinc plating operation was conducted using the bath under the conditions such as the temperature of 35C.
• the pH adjusted to 7.2 with ammonia water and the current density of 2 A/dm for l0 minutes.
• the obtained deposit metal had high brilliance and softness.
• a zinc plating bath was'prepared by adding 5 g/l of H O (CH CH SO Na, 3 g/l of HS (CH- C- H 055 SO Na and 3 g/l of 4-carboxyisoquinone and 0.3 g/l of 5chloro-B-acethyl-naphton to the fundamental composition comprising 30 g/l of zinc chloride and 250 g/l of ammonium chloride and a zinc plating operation was conducted using the bath under the conditions such as the temperature of about 30C, the pH of about 5.0 and the current density of 2 A/dm for 10 minutes. The obtained deposit metal had a high brilliance.
• An aqueous cyanide-free zinc electroplating bath containing (a) a water soluble zinc salt selected from the group consisting of zinc chloride, zinc sulfate and zinc sulfaminate, a water-soluble ammonium salt selected from the group consisting of ammonium chloride, ammonium sulfate and ammonium acetate, and optionally a hydroxycarboxylic acid; (b) from 0.1 to 30 gm/liter of at least one sulfate compound of the formula wherein A is selected from the group consisting of hydrogen, C,,H with n being an integer of 4 to 20, al-
• kylphenyl, sorbitol, mannitol, alkylpolyamine B is a member selected from the group consisting of H O) and CONH
• M is selected from the group consisting of hydrogen, ammonium, alkali metal, alkaline earth metal and zinc; (c) from 0.01 to 5.0 gm/liter of at least one alkylnaphthylketone of the formula ll R ⁇ N/ COOH wherein is a heterocyclic ring selected from the group consisting 14- of 5151151; in which s aid bath confiifi sTro mfi3 to 2f5 gm/liter of said alkylnaphthylketone.

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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)
• Other In-Based Heterocyclic Compounds (AREA)
• Pyridine Compounds (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Quinoline Compounds (AREA)

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Cited By (9)

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Citations (7)

• 1970
  • 1970-04-24 JP JP45034717A patent/JPS4840543B1/ja active Pending
• 1971
  • 1971-04-07 US US00132218A patent/US3787296A/en not_active Expired - Lifetime
  • 1971-04-23 FR FR7114516A patent/FR2086320B1/fr not_active Expired
  • 1971-12-21 GB GB1053871*[A patent/GB1327291A/en not_active Expired

Patent Citations (7)

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