US3674655A - Surface preparation of uranium parts - Google Patents

Surface preparation of uranium parts Download PDF

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Publication number
US3674655A
US3674655A US790869A US3674655DA US3674655A US 3674655 A US3674655 A US 3674655A US 790869 A US790869 A US 790869A US 3674655D A US3674655D A US 3674655DA US 3674655 A US3674655 A US 3674655A
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United States
Prior art keywords
uranium
pickling
lithium
degreasing
chemical
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Expired - Lifetime
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US790869A
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English (en)
Inventor
Louis De Vaulchier Du Deschaux
Alain De Fouchier
Emmanuel De Vaucelles
Louis Facquet
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Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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Commissariat a lEnergie Atomique CEA
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
    • C25F3/00—Electrolytic etching or polishing
    • C25F3/02—Etching
    • C25F3/10—Etching of actinides
    • 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
    • C25D5/34—Pretreatment of metallic surfaces to be electroplated
    • C25D5/46—Pretreatment of metallic surfaces to be electroplated of actinides

Definitions

  • ABSTRACT Prior to electroplating parts of uranium or uranium base al- [30] Foreign Application Priority Data loys, the parts are sub ected to a surface preparat on which comprises preliminary steps of chemical degreasmg, elec- Jan. 24, 1968 France ..68l373l2 trolytic degreasing and if necessary of chemical etching and further comprises an anodic electrolytic treatment in an aque- [52] U.S. Cl ..204/1.5, 204/141 ous l ti f a r anic alt or a sulphate of lithium and/or [51] Int. magnesium [58] Field of Search ..204/1.5
  • the present invention relates to surface preparation of parts formed of unalloyed uranium or of uranium rich alloys such as those which contain Va, Zr, Pu, Mo, Cr, etc such surface preparation is necessary prior to forming metallic coating and in particular electrolytic coatings on the parts.
  • the base metal may of course consist of a material constituting the whole of the part or of a conductive coating previously deposited on the part.
  • An important purpose of the surface preparation is to clean or scrape the part to be plated and to remove any layer of foreign substances such as grease, oxides, scale and the like which may normally be present on the surface of the base metal.
  • ordinary metals such as iron, copper or their alloys
  • a number of different conventional methods of preparation produce satisfactory results.
  • One method which is commonly employed starts with chemical degreasing by means of an organic solvent such as trichloroethylene, electrolytic degreasing carried out at the cathode of a sodium hydroxide bath, washing and pickling.
  • an additional process which can be mentioned by way of example consists of anodic pickling in an aqueous sulphuric acid solution.
  • the process adopted consists of chemical pickling in a solution containing nitric acid as well as a number of different constituents which may be required. It has also been proposed to carry out electrolytic pickling in strongly acid aqueous solutions of various salts, especially salts of alkali metals. After the pickling process in which the surface of the metal to be treated is completely exposed, the part is washed and the plating operation is then carried out; in the case of electrodeposition of one metal, the part which is withdrawn from the washing bath is immediately placed in the plating bath which corresponds to the desired metal.
  • the process referred to comprises the following operations:
  • This chemical cleaning and pickling process permits the formation of highly adherent electrodeposited coatings on the cleaned surface of the uranium but is nevertheless subject to a number of drawbacks.
  • the base-metal surface which is obtained as a result of this cleaning process does not have a metallic appearance but remains covered with a greyish film which can be considered to have a detrimental eflect on the quality of adhesion of the plated coating on the uranium although a good standard of adhesion is nevertheless achieved.
  • the film referred to can in some instances retain water or traces of baths in which the part has been treated and therefore can subsequently cause attack of the uranium beneath the plated coating, such attacking action being in turn liable to result in loss of adhesion or even in destruction of the coating.
  • the attack of the pure or alloyed uranium by the different baths mentioned in the foregoing is variable; in particular, the sensitivity to different reagents is dependent on the alloy being treated and consequently makes it necessary to adapt the concentrations and periods of attack in the case of each alloy.
  • the resultant chemical action can frequently be violent, is sometimes irregular, and can give rise to dissolution of the base metal at variable depths, to uncertainty in regard to compliance with dimensional requirements and in regard to the weight of remaining uranium of treated parts and therefore results in a dispersion of the results ob tained. in consequence, it becomes necessary to carry out a minute inspection of the treated parts.
  • the surface of the base metal is rough and irregular after chemical attack, especially in the case of alloys. This is detrimental to the quality of the electrolytic coatings which are deposited and especially to their imperviousness, thus reducing the value of such coatings from the point of view of protection against corrosion.
  • the part is dipped in the pickling bath for a period of two minutes, then washed, dipped in nitric acid for another period of 2 minutes, washed, dipped in the pickling bath for a further period of 1 minute, then washed followed by further dipping nitric acid for 2 minutes, then finally subjected to final washing and placed in the electroplating bath.
  • This process is less aggressive and makes it possible to obtain a chemical attack which is less violent than the method of preparation described in the French Pat. No. 1,523,216 cited earlier.
  • the inventors have also given consideration in the past to a number of different methods which are based on electrolytic anodic attack and intended to reduce the above-mentioned disadvantages even further.
  • they have developed a method based on the use of sodium acetate which comprises the following steps:
  • electrolytic anodic pickling in a sodium acetate solution containing 400 g/l of NaCH CO 3H O having a pH of 6 (adjustment of the pH value being carried out by means of acetic acid) at a current density of 7 A/dm and for a period of 15 minutes at 25 C.
  • the part which is delivered from the washing stage is then placed in the electroplating bath (nickel-plating bath, for example) and the plating operation is immediately begun.
  • the electroplating bath nickel-plating bath, for example
  • the electrolytic pickling process last mentioned constitutes a substantial improvement over comparable processes of the prior art.
  • the cleaned part has a much lower degree of surface roughness, the appearance of the cleaned surface is more uniform, the quantity of metal removed in the pickling process is much more readily controlled by adjusting the current density and the duration of the process and the dimensional changes which result from the pickling process can be predetermined with a better approximation.
  • the object of the invention is to remove or at least to attenuate these defects even further to yet a very appreciable extent.
  • the 'mvention proposes a method of surface preparation which comprises at the same time as conventional steps of degreasing, rinsing and possibly of chemical pickling anodic pickling in an aqueous solution containing an organic salt or a sulphate of lithium and/or magnesium.
  • This method provides a marked improvement over the methods described in the foregoing by virtue of the fact that, instead of only employing anions for the electrolytic anodic pickling process as has been the practice up to the present time, the invention utilizes at the same time the cation of the salt employed.
  • the results are radically different from those obtained as a result of the use of other cations such as the acetates of sodium, potassium, ammonium, zinc, cadmium and so forth.
  • the pickling process under consideration can be preceded by the following operations:
  • Anodic pickling can be followed by:
  • This method appears to be in general in scope and to be applicable to depleted, natural or enriched uranium as well as to the majority of uranium alloys.
  • the density (and correlatively the potential) of the currents employed in the anodic pickling process is distinctly lower than the values which were formerly considered necessary, with the result that the attack is less violent, that the thickness of the uranium layer which is removed as a result of pickling is small, uniform and readily controlled, that the final dimensions of parts can be determined prior to treatment and that the surface properties which a part may have acquired during previous metallurgical processes (especially work-hardening) are retained.
  • the bath can be employed for a much greater number of operations and precipitates a much smaller quantity of insoluble substances, in particular when lithium salts are employed. This last aspect is significant when there is an attendant danger of criticality.
  • the state of surface both of the base metal and of the electrolytic coating formed on the base metal are improved to a very substantial extent, the plated coating which is obtained has a much more uniform structure and, for equal thickness, the continuity and imperviousness of said coating are highly improved. From the point of view of protection against corrosion, this coating is of considerably greater value than the coatings obtained up to the present time. Adhesion of the plated coating on uranium is at least comparable with the coatings obtained by other methods but surface roughness has been reduced to a considerable extent and this in turn results in an improvement in the protective value of the coating.
  • the part was a cylinder of uranium alloy containing 1.5 percent molybdenum, having a diameter of 40 mm and a length of 299 mm, a surface area of 400 cm and a weight of 6,905 grams.
  • a threaded bore having a diameter of 10 mm and a depth of 15 mm was formed at one end of the part and along the axis of the cylinder.
  • a threaded rod which served to support the part and to supply current to this latter was screwed into said bore; the entire surface of the uranium alloy could thus be immersed. All sharp edges and comers of the part were rounded ofi so as to have a radius of 2 mm.
  • the part thus prepared was degreased by means of trichloroethylene for a period of 2 minutes, then placed at the cathode in an electrolytic degreasing bath consisting of a normal sodium hydroxide solution for a period of 3 minutes at 40 amps, namely A/dm the appearance of the surface remained unchanged and this operation resulted in an insignificant weight loss of the order of 10 mg.
  • the part was subjected to chemical pickling for a period of one minute in a 7 N nitric acid solution at 21 C. No apparent reaction was observed and the weight loss of the part was approximately 20 mg.
  • the part was then pickled in a 7 N nitric acid solution at ambient temperature for a period of 1 minute. During this operation, a few remaining traces of the black film were dissolved and the weight loss was approximately 40 mg.
  • the part was then carefully washed with cold running water and placed as rapidly as possible in a nickel-plating bath through which a current was passed.
  • the anodic pickling operation was then carried out for a period of 15 minutes in a lithium tartrate solution having a Li concentration of 2 N at a current density of 7 A/dm and at a temperature of 21 C. Agitation of the solution was maintained. The initial pH of the solution was 6.00 and the final pH was 6.01.
  • Example 1 The black film was removed during the subsequent washing operation and more readily than in the case of pickling with magnesium acetate; the pickled subadjacent metal then exhibited a grey color. The weight lost by the part during this operation was 10.18 g.
  • the part On completion of the washing operation, the part was dipped for a period of 1 minute in a 7 N nitric solution, then carefully washed and placed in the plating bath as indicated in Example 1.
  • a method of operation which is similar to the preceding was applied to a cylindrical part having a diameter of 35 mm, a length of 4 mm, a weight of 72.13 g and formed of uranium containing 0.2 weight percent of vanadium.
  • the part which was degreased with trichloroethylene for a period of 2 minutes was placed at the cathode in a normal sodium hydroxide bath at 2.4 Amps (namely 10 A/dm) for a period of 3 minutes.
  • the part was washed then pickled for a period of 1 minute at 21.5" C in a 7 N nitric acid solution. No apparent reaction was observed and the weight loss was 4.8 mg.
  • a similar mode of operation was applied to a uranium part containing 1.5 percent molybdenum, having a diameter of 35 mm, a length of 4 mm and a weight of 70. 16 g. Electric current was supplied through a threaded rod which was screwed into the part.
  • the part was degreased for a period of 2 minutes in toluene, subjected to a cathodic degreasing for 3 minutes in a normal sodium hydroxide solution at a current density of 10 A/dm, then washed and finally pickled for one minute in a 7 N nitric acid solution at 23 C.; no apparent reaction was observed and the weight loss was 1.8 mg.
  • Anodic pickling was carried out on completion of the washing operation.
  • the part was subjected to vertical vibrations and immersed in a lithium sulphate solution having a Li concentration of 4 N, said solution being brought to a pH of 0 by addition of H 80, pickling was carried out at 6 A/dm at 23 C. for a period of 20 minutes.
  • the part was carefully washed and immediately placed under tension in a nickel-plating bath.
  • lithium nitrate or magnesium nitrate would produce completely different results of the same kind as those obtained by nitric acid attack (which may form part of the chemical pickling which precedes the anodic pickling process), in which case an irregular attack would be obtained.
  • the invention can be extended to many alternative applications, all of which entail either one or a number of anodic pickling processes in solutions of lithium or magnesium salt. It is possible to modify the composition of the baths, to vary the concentration of the constituents or to add a number of different products such as surface-active agents, for example it is possible to carry out degreasing and/or anodic pickling operations (or anodic and cathodic pickling in alternate sequence), to vary the times, the current densities, the temperatures and the pH values in order to take into account both the composition and volume of parts being treated.
  • a method of surface preparation of parts whose superficial portion at least consists of uranium or uranium-rich alloy which method comprises making the part anodic in an aqueous solution of a salt selected from the group consisting of sulphates, acetates, citrates, tartrates, oxalatesn malates, lactates, formiates, melonates, pyrogallates and succinates of lithium and magnesium at current densities of from 2 to 20 A/dm.
  • a salt selected from the group consisting of sulphates, acetates, citrates, tartrates, oxalatesn malates, lactates, formiates, melonates, pyrogallates and succinates of lithium and magnesium at current densities of from 2 to 20 A/dm.
  • a method of surface preparation of parts of uranium and uranium base alloys comprising preliminary steps of chemical degreasing and electrolytic degreasing and further comprising an anodic electrolytic treatment in an aqueous solution of a salt selected from the group consisting of the organic salts and sulphate of lithium and magnesium, at current densities of from 2 to 20 A/dm'.

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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 Methods And Accessories (AREA)
US790869A 1968-01-24 1969-01-13 Surface preparation of uranium parts Expired - Lifetime US3674655A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR137312 1968-01-24

Publications (1)

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US3674655A true US3674655A (en) 1972-07-04

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US (1) US3674655A (no)
BE (1) BE726712A (no)
DE (1) DE1903580A1 (no)
FR (1) FR1564575A (no)
IL (1) IL31402A0 (no)
LU (1) LU57717A1 (no)
NL (1) NL6901040A (no)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4437926A (en) 1980-07-07 1984-03-20 Regie Nationale Des Usines Renault Metal alloy with high catalytic activity
US4803098A (en) * 1985-11-19 1989-02-07 Commissariat A L'energie Atomique Process for the preparation of the surface of a uranium and titanium alloy member, particularly with a view to chemical nickel plating
CN108277490A (zh) * 2018-01-18 2018-07-13 中国原子能科学研究院 铀箔的表面处理方法

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2567913B1 (fr) * 1984-07-18 1989-11-10 Commissariat Energie Atomique Procede de preparation de la surface de pieces en uranium ou en alliage a base d'uranium
US4585530A (en) * 1985-08-09 1986-04-29 M&T Chemicals Inc. Process for forming adherent chromium electrodeposits from high energy efficient bath on ferrous metal substrates

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2853441A (en) * 1949-09-29 1958-09-23 Flint Oliver Surface treatment of uranium
US2872387A (en) * 1948-05-12 1959-02-03 Kolodney Morris Anodic treatment of uranium
US2894883A (en) * 1949-07-18 1959-07-14 David E Walker Method of electropolishing uranium

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2872387A (en) * 1948-05-12 1959-02-03 Kolodney Morris Anodic treatment of uranium
US2894883A (en) * 1949-07-18 1959-07-14 David E Walker Method of electropolishing uranium
US2853441A (en) * 1949-09-29 1958-09-23 Flint Oliver Surface treatment of uranium

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4437926A (en) 1980-07-07 1984-03-20 Regie Nationale Des Usines Renault Metal alloy with high catalytic activity
US4803098A (en) * 1985-11-19 1989-02-07 Commissariat A L'energie Atomique Process for the preparation of the surface of a uranium and titanium alloy member, particularly with a view to chemical nickel plating
CN108277490A (zh) * 2018-01-18 2018-07-13 中国原子能科学研究院 铀箔的表面处理方法

Also Published As

Publication number Publication date
FR1564575A (no) 1969-04-25
LU57717A1 (no) 1969-04-21
DE1903580A1 (de) 1969-08-21
IL31402A0 (en) 1970-01-29
NL6901040A (no) 1969-07-28
BE726712A (no) 1969-06-16

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