US3853593A - Process for improving the protective properties of chromium-oxide based compound coatings, by means of stabilization of the chromium ion - Google Patents

Process for improving the protective properties of chromium-oxide based compound coatings, by means of stabilization of the chromium ion Download PDF

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Publication number
US3853593A
US3853593A US00270291A US27029172A US3853593A US 3853593 A US3853593 A US 3853593A US 00270291 A US00270291 A US 00270291A US 27029172 A US27029172 A US 27029172A US 3853593 A US3853593 A US 3853593A
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United States
Prior art keywords
chromium
oxide based
improving
group
solution
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Expired - Lifetime
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US00270291A
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English (en)
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G Baudo
G Bombara
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Centro Sperimentale Metallurgico SpA
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Centro Sperimentale Metallurgico SpA
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/82—After-treatment
    • C23C22/83—Chemical after-treatment

Definitions

  • the present invention covers a process and a composition for improving the protective properties of chromium oxide based compound coatings by means of stabilization of the chromium ion. More particularly the invention coversthe improvement of the protective properties of thin chromium oxide based coatings, by means of a superficial stabilization processing of the chromium ion, based on the chelating action exerted upon the same ion, by the beta-diketones.
  • Tin-Free Steels Chromium-Type resulted as the most suitable for the substitution of tin in the tin plate used for food containers.
  • tin is substituted with a thin compound coating of chromium-chromium oxide (of the order of a few tenths of a micron).
  • the chromium oxide has the twofold function of sealing the microporosities presented by the chromium layer which is thin on account of economy and stability, and of supplying a very good anchorage basis for the application of protective varnishes or paints.
  • the object of thepresent invention is precisely improving the sealing action of chromium oxide upon the microporosities of the coating, increasing, in the same time, the adhesion of the varnish to the substratum.
  • this purpose is fulfilled by means of stabilization of the chromium ion.
  • This stabilization is obtained, on the basis of the present invention, by blocking the chromium ions into chelated complexes insoluble in water, obtained by reaction of the chromium ion with the beta-diketones corresponding to the general formula:
  • the complexing action of the beta-diketones determines a decrease of the porosity of the coating which becomes more compact and therefore develops a more efficacious protective action.
  • beta-diketones in aqueous solution originate an equilibrium wherein the following tautomeric forms participate (which forms are distinguishable for the migration of a hydrogen atom from a carbon atom to the adjacent carbon atom):
  • the radical R may be chosen among the monovalent radicals derived from aromatic type rings, either condensed or not, either containing hetero atoms or not.
  • the choice of the radical R is effected among the electrons acceptor functional groups, the inductive effect of which implies an impoverishment of the electronic density of the enolic group.
  • the detachment of the proton H bound to it is favoured, and, therefore, the acidity of the enolic group itself is enhanced.
  • R is a monovalent radical, such as the phenyl group C H the thenyl group C H S, the naphthyl group C H the pyrryl group C H N and the p. fluoro phenyl group C H. ,F.
  • R is a monovalent radical able to impoverish the electronic density of the enolic group by inductive effect, such as the trichloro-methyl group CCl or trifluoro-methyl group CF heating the solution prepared as hereinbefore described at a temperature ranging from 30 to 90C;
  • the present invention provides the addition of a nonionic surface active agent in a concentration up to 1% by weight to the processing solution.
  • This surface active agent facilitates the formation of a dispersion.
  • the present invention process is not limited to the case of the coatings based on chromium-chromium oxide. In fact it can be also applied in all these cases wherein a film of chromium oxide is used to seal the porosity of any metallic coating.
  • the porosity of the coating is measured by means of an electro-chemical technique, consisting of the determination of the potentiodynamic anodic curve of the said material in an aggressive medium.
  • the maximum density of the current of the anodic dissolution of the substratum is directly proportional to the degree of the porosity of the coating. M is the maximum of the current density of the material before the treatment, M is that of the material after the treatment.
  • EXAMPLE 1 The material to be treated is a carbon steel (black sheet-steel) electrolytically coated with a film with the following composition:
  • the material to be treated is a carbon steel (black sheet-steel) electrolytically coated with a film with the following composition:
  • the untreated material presents a maximum of current density M equal to 0.21 mA/cm after the treatment the maximum M is 0.12 mA/cm
  • the material to be treated is a carbon steel (black steel-sheet) electrolytically coated with a film with the following composition:
  • the untreated material present a maximum of current density lVl equal to 0.21 mA/cm while after the treatment the maximum M is 0.13 mA/cm
  • the present invention has been described with particular reference to the specific embodiments thereof, but it is intended that modifications and variations may be introduced therein, without infringing the protection limits of the invention.
  • a process for improving the protecting properties of chromium oxide based coatings comprising immersing a metal substrate having thereon a chromium oxide based coating, in an aqueous solution of 0.1 to 10 grams per liter of a beta-diketone of the formula in which R is a monovalent aromatic ring-containing radical and R is a monovalent radical able to impoverish the electronic density of the enolic group by inductive effect, at a temperature from 30 to 90C., for 1 second to minutes, with constant stirring, then 0 rinsing the coated substrate in water and drying the surface of the coating.
  • R is a member selected from the group consisting of phenyl, thenyl, furyl, naphthyl, pyrryl and fluoro-phenyl.
  • R is a member selected from the group consisting of trifluoromethyl and trichloro-methyl.

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  • Chemical & Material Sciences (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Chemical Treatment Of Metals (AREA)
  • Paints Or Removers (AREA)
  • Electrochemical Coating By Surface Reaction (AREA)
  • Electroplating And Plating Baths Therefor (AREA)
US00270291A 1971-07-31 1972-07-10 Process for improving the protective properties of chromium-oxide based compound coatings, by means of stabilization of the chromium ion Expired - Lifetime US3853593A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
IT5204271 1971-07-31

Publications (1)

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US3853593A true US3853593A (en) 1974-12-10

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Country Status (5)

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US (1) US3853593A (OSRAM)
JP (1) JPS553439B1 (OSRAM)
BE (1) BE786634A (OSRAM)
FR (1) FR2148023B1 (OSRAM)
GB (1) GB1394244A (OSRAM)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4070521A (en) * 1975-03-20 1978-01-24 Diamond Shamrock Corporation Methylene chloride phosphatized coating
US4210498A (en) * 1974-11-20 1980-07-01 Matsushita Electric Industrial Co., Ltd. Method of increasing the amplification of a transistor through use of organic compounds

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3484343A (en) * 1964-07-13 1969-12-16 Toyo Kohan Co Ltd Amine solution treatment of cathodically chromated metal surfaces
US3567599A (en) * 1967-06-21 1971-03-02 Inland Steel Co Electrochemical treatment of ferrous metal
US3615888A (en) * 1969-09-04 1971-10-26 American Cyanamid Co Chemical treatment of metal
US3761303A (en) * 1971-12-07 1973-09-25 Us Air Force Method for impregnating microcracks in chromium plating

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3484343A (en) * 1964-07-13 1969-12-16 Toyo Kohan Co Ltd Amine solution treatment of cathodically chromated metal surfaces
US3567599A (en) * 1967-06-21 1971-03-02 Inland Steel Co Electrochemical treatment of ferrous metal
US3615888A (en) * 1969-09-04 1971-10-26 American Cyanamid Co Chemical treatment of metal
US3761303A (en) * 1971-12-07 1973-09-25 Us Air Force Method for impregnating microcracks in chromium plating

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4210498A (en) * 1974-11-20 1980-07-01 Matsushita Electric Industrial Co., Ltd. Method of increasing the amplification of a transistor through use of organic compounds
US4070521A (en) * 1975-03-20 1978-01-24 Diamond Shamrock Corporation Methylene chloride phosphatized coating

Also Published As

Publication number Publication date
DE2236301A1 (de) 1973-02-08
JPS553439B1 (OSRAM) 1980-01-25
BE786634A (fr) 1972-11-16
GB1394244A (en) 1975-05-14
FR2148023B1 (OSRAM) 1974-10-04
DE2236301B2 (de) 1975-06-19
FR2148023A1 (OSRAM) 1973-03-11

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