EP0783598A1 - Procede de chromage et bain de chromage contenant des polychromates - Google Patents

Procede de chromage et bain de chromage contenant des polychromates

Info

Publication number
EP0783598A1
EP0783598A1 EP96925681A EP96925681A EP0783598A1 EP 0783598 A1 EP0783598 A1 EP 0783598A1 EP 96925681 A EP96925681 A EP 96925681A EP 96925681 A EP96925681 A EP 96925681A EP 0783598 A1 EP0783598 A1 EP 0783598A1
Authority
EP
European Patent Office
Prior art keywords
chromium
polychromates
bath
sulphonamides
salts
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.)
Granted
Application number
EP96925681A
Other languages
German (de)
English (en)
Other versions
EP0783598B1 (fr
Inventor
Giovanni Merello
Lido Frediani
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Luigi Stoppani SpA
Original Assignee
Luigi Stoppani SpA
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 Luigi Stoppani SpA filed Critical Luigi Stoppani SpA
Priority to EP96925681A priority Critical patent/EP0783598B1/fr
Publication of EP0783598A1 publication Critical patent/EP0783598A1/fr
Application granted granted Critical
Publication of EP0783598B1 publication Critical patent/EP0783598B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

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
    • C25D3/04—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 a process and a bath for chromium- plat ing by electrodeposition from a polychromate- based solution.
  • Polychromate-based chromium- plat ing baths have been known since 1933. They are usually prepared by mixing chromium anhydride and sodium hydroxide in solution. A characteristic of polychromate-based chromium-plating baths is that they use high current densities and maintain high cathode efficiencies - 30% or more.
  • polychromate- based chromium plating baths have a number of disadvantages which have limited their use on an industrial scale.
  • the deposit obtained is dull and has low covering power; it is difficult to prepare the polychromate-based chromium-plating baths on an industrial scale and, usually, the temperature of the bath must not exceed 20°C. Chromic-acid based chromium-plating baths are normally used to give brighter deposits, but these give low cathode efficiencies .
  • the present invention relates to a process for chromium-plating by electrodeposition of chromium from a bath comprising polychromates and sulphates, characterized by effecting the said electrodeposition in the presence of sulphonamides of formula R-S0 2 Y, where R is an alkyl chain and Y is an amine group, and in which the ratio of carbon atoms in the R chain and nitrogen atoms in the amino group
  • Y is ⁇ 12, or of the corresponding sulphonimides.
  • the invention also relates to a chromate bath for the realization of the above process.
  • the sulphonamide used has the general formula R-SC -NR'R", where R is a linear alkyl chain C1-C12, R' and R" are, together or separately, hydrogen, -NH 2 , -NHOH, -CONH 2 or an aliphatic or heterocyclic substituent.
  • Na, Mg or ammonium salts of alkyl sulphonic acids of the general formula R-SO3-, where the ratio between the sulphur atoms and the carbon atoms in the R chain is greater or equal to 1/4, (S:C ⁇ 1:4), or corresponding salts of sulfamic acid, are used to increase the covering power of the bath and to give extensive substantially uniform micro-cracking in the presence of selenium.
  • Some of these compounds were obtained in the presence of chromium borate as initiator.
  • the preferred concentration of such compound in the bath was between 4 and 40 g/litre.
  • the preferred operating temperature is between 40 and 70°C and more preferably, between 45 and 60°C.
  • the ratio of polychromate concentration to sulphate concentration is preferably between 20 and 250. The deposits obtained from these baths are dull and have low covering power.
  • Short-chain alkyl sulphonic acids have been used as additives in some of the known electroplating processes to increase the cathode efficiency of the bath (in chromic acid based baths) as described, for instance, in EP-A- 0196053.
  • the alkyl sulphonic acids have the disadvantage of causing electrochemical corrosion of anodes in Pb/Sn and in other lead-based alloys. This corrosion occurs both in the chromic acid based chromium baths and in polychromate based baths as in the present invention, though in the latter it is in a reduced form due to the less acid pH of the same.
  • the sulphonamides and the sulphonimides have the same function in protecting the anode even in traditional baths based on chromic acid and sulphuric acid.
  • the use of sulphonamides and sulphonimides in such traditional baths has been found to have other advantages, in particular, to lead to higher cathode efficiency and brighter deposits.
  • a further object of the invention is thus the use of sulphonamides or sulphonimides according to Claim 14.
  • the sulphonimides preferably used in the present invention are generally prepared by the Schotten and Baumann reaction of chlorides of C1-C12 alkyl sulphonic acids:
  • Ammonium compounds such as hydroxylamine, hydrazine, urea, aliphatic or heterocyclic amines may be used instead of ammonia.
  • the aliphatic amines are preferably primary amines with aliphatic C1-C12 chain.
  • the sulphonamides of interest for the present invention are those mentioned above with the general formula R-S0 2 - NR'R", where R is a C1-C12 alkyl chain and R' and R" are, together or separately, hydrogen, -NH 2 , -NHOH, -CONH 2 or an aliphatic or heterocyclic substituent.
  • Preferred concentrations of sulphonamides are such as to give a ratio of the concentration (by weight) of polychromate to the concentration (by weight) of sulphonamide of between 20 and 450.
  • Such ions are present (either alone or in combination) in total concentrations of from 2 to 30 g/1 in addition to any such cations that are possibly present in the polychromates used.
  • cations are preferably added to the bath in the form of contra-ions of the organic anions of alkyl sulphonic acids R-S0 3 H, where R is a C1-C4 alkyl group with possible substitution in the 2 position by -OH or -NH2.
  • Preferred salts are Na, Mg or ammonium salts of CH 3 S0 3 " ; CH 3 CH 2 S0 3 " ;
  • the preferred concentration of the alkylsulphonic salts are thos e whi ch give s a rati o of polychromate concentration (by weight) to alkyl sulphonic acids concentration (by weight) between 25 and 450.
  • a further advantage of using the cations referred to above is that they produce very extensive micro-cracking in the presence of selenium even in areas of reduced current density.
  • the process according to the invention provides, having prepared a bath giving the characteristics listed above, for operation at a current density of between 11 and 230
  • A/dm and preferably between 30 and 100 A/dm .
  • the bath according to the present invention produces a bright, adhering and non-iridescent deposit on a metal base, free of grey or rough deposit at low current-density with a cathode efficiency of at least 25% measured at a current density of 50 A/dm 2 and a chromate bath temperature of 52°C.
  • a chromate bath was prepared , based on tri - and tetra- chromates with the following initial composition :
  • Sulphonamides were added to the bath of Example 1 in a series of steps to give from 2 g/1 to 12 g/1.
  • the cathode efficiency was still 25%.
  • the deposit was bright in all concentrations of the example.
  • the cathode used in this bath was a 1.5 X 15 cm "V"-shaped panel.
  • the chromium plating was carried out at a current of 10 A.
  • the distance of the plating from the base of the indentation was the following:

Abstract

Selon l'invention, on ajoute à un bain de chromage, contenant des polychromates et des sulfates, des sulfamides et des sulfonamides afin de produire des dépôts clairs et d'inhiber la corrosion de l'anode, et des cations de Na, Mg et d'ammonium pour accroître le pouvoir couvrant.
EP96925681A 1995-07-28 1996-07-08 Procede de chromage et bain de chromage contenant des polychromates Expired - Lifetime EP0783598B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP96925681A EP0783598B1 (fr) 1995-07-28 1996-07-08 Procede de chromage et bain de chromage contenant des polychromates

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
EP95830339 1995-07-28
EP95830339 1995-07-28
PCT/EP1996/002983 WO1997005301A1 (fr) 1995-07-28 1996-07-08 Procede de chromage et bain de chromage contenant des polychromates
EP96925681A EP0783598B1 (fr) 1995-07-28 1996-07-08 Procede de chromage et bain de chromage contenant des polychromates

Publications (2)

Publication Number Publication Date
EP0783598A1 true EP0783598A1 (fr) 1997-07-16
EP0783598B1 EP0783598B1 (fr) 1999-03-03

Family

ID=8221986

Family Applications (1)

Application Number Title Priority Date Filing Date
EP96925681A Expired - Lifetime EP0783598B1 (fr) 1995-07-28 1996-07-08 Procede de chromage et bain de chromage contenant des polychromates

Country Status (4)

Country Link
EP (1) EP0783598B1 (fr)
DE (1) DE69601618T2 (fr)
ES (1) ES2131405T3 (fr)
WO (1) WO1997005301A1 (fr)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1215304A1 (fr) * 2000-12-06 2002-06-19 Lido Frediani Procédé de placage de chrome en deux couches
CN104476939B (zh) * 2014-12-25 2017-07-14 东莞运城制版有限公司 一种版辊的镀铬方法及保管方法

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH673845A5 (en) * 1987-07-02 1990-04-12 Sosh Ag Synergistic additive mixt. for chromic acid electrolyte - contg. propionic, butyric and valeric acid in specified ratio

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9705301A1 *

Also Published As

Publication number Publication date
DE69601618T2 (de) 1999-11-11
EP0783598B1 (fr) 1999-03-03
DE69601618D1 (de) 1999-04-08
ES2131405T3 (es) 1999-07-16
WO1997005301A1 (fr) 1997-02-13

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