Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
  • C25F1/00—Electrolytic cleaning, degreasing, pickling or descaling
  • C25F1/02—Pickling; Descaling
  • C25F1/04—Pickling; Descaling in solution

Definitions

• This invention relates to the process for pickling beryllium containing copper alloys and it relates not only to copper alloys containing 1.8-2% beryllium but also to such alloys which may contain small amounts of nickel and/or cobalt and to ternary alloys containing 0.4 to 0.7% beryllium, 1.2-2.5 nickel or 2.3 to 2.7% cobalt.
• pickling is carried out in an aqueous solution containing 20-50% by volume sulphuric acid. The operation is carried out at a temperature within the range of 40-60 C. by immersion for 10-60 minutes, depending somewhat on the degree of oxidation. After rinsing with water, the part is immersed for a few seconds in a chromatosulphuric mixture containing 50 g. chromic acid and 150 cc. of sulphuric acid (66 B.) in 850 g. of water. This process is slow and the treated surface has an irregular appearance. With alloys of copper, cobalt and beryllium, pickling is not complete.
• the operation is carried out at a temperature within the range of 40-70 C. in a bath containing 50 g. chromic acid and 150 cc. sulphuric acid (66 B.) in 850 g. of water. Treatment is effected for one minute to produce a satisfactory surface even with copper-cobaltberyllium alloys. Unfortunately, the process is troublesome because the bath deteriorates rapidly by reason of the reduction of the chromic acid in the bath.
• the usual chemical pickling process is replaced by an electrolytic pickling process in which use is made of an aqueous electrolyte solution containing at least one alkali metal halide and a surface active agent.
• the process of this invention is applied to the cleaning of copper-beryllium alloys having an oxide layer, such as the type produced during thermal treatment of the alloy, even when carried out in an inert atmosphere.
• the metal to be pickled is connected to the anode of a direct current generator while the cathode is an inert conductor, such as stainless steel.
• the electrolysis bath is formulated of a solution of sodium chloride in water with a surface active agent to assist in the removal of the greyish black oxide which forms as a deposit during pickling. The wetting agent releases the deposit for removal.
• the concentration of materials making up the electrolyte and the operating conditions, such as current density, can be varied over fairly wide limits.
• concentration of sodium chloride or other alkali metal halide can be varied within the range of and 200 g. per liter.
• the pH of the bath can vary within the range of 5.5 to 8.5 and the temperature of the bath can be varied within the range of 25-45 C.
• the voltage at the terminals is of the order of about 2 volts with a current density within the range of 3-5 amperes per square decimeter.
• wetting or surface active agent use can be made of an alcohol or a commercial wetting agent such as an anionic, cationic or nonionic surface active agent which is compatible with the pH of the bath and which are of the type described in Oil and Soap, vol. XVII, No. 9, September 1941 (pages 179-182), by Harris, Epstein & Kohn.
• the amount of wetting agent depends upon its composition. If an alcohol is used, such as ethanol or methanol, the amount employed should be within the range of 50- 100 g. per liter. In the event that use is made of a commercial surface active agent, the amount generally employed is within the range of 1-5 g. per liter.
• the pickling treatment can be varied from 2-15 minutes depending somewhat on the thickness and character of the oxide layer on the metal surface. After pickling, the part is rinsed with water to remove electrolyte and then dried.
• EXAMPLE 1 Strips of copper-beryllium alloy having 1.9% by Weight of beryllium and 0.3% by weight of copper, tempered in an inert atmosphere had an oxidized surface following tempering treatment. The strips were pickled by electrolysis in an aqueous bath containing 200 g. per liter sodium chloride and 77 cc. per liter methanol.
• the cathode was formed of stainless steel plate and the strip of metal was connected to the anode and passed through the electrolytic bath at a speed such that the residence time in the electrolyte was 3 minutes.
• the voltage at the terminals was 2 volts and the current density was amperes per square decimeter.
• the strip Upon removal from the bath, the strip was rinsed in clean running water and dried, and the metallic appearance obtained was very uniform.
• EXAMPLE 2 The elements, consisting of copper-cobalt-beryllium alloy, having 2.5% by weight cobalt and 0.5% by weight of beryllium, were oxidized during thermal treatment and suspended from the anode for immersion in a bath containing 150 g. per liter sodium chloride and 2 g. per liter Celanol A (a neutral polyethoxyether surface active agent).
• metal halides and other surface active agents may be employed in the processes of Examples 1 and 2 without departing from the spirit of the invention, and other changes may be made in the details of formulation and operating conditions without departing from the spirit f the invention, especially as defined in the following claims.
• a process for pickling copper based alloys including at least 0.4% beryllium and up to 2.5% nickel or up to 2.7% cobalt comprising the steps of connecting the alloy with the anode in a direct current electrolysis bath in which the bath consists essentially of an aqueous solution of an effective amount of a salt supplying chloride ions and a surface active agent, adjusting the pH of the bath to a value within the range of 5.5 to 8.5, and applying an electrical current between the anode and cathode at a current density which does not effect metal removal and while maintaining the bath at a temperature within the range of from about C. to about 45 C.
• the surface active agent is selected from the group consisting of an anionic, cationic and nonionic surface active agent present in an amount within the range of l-5 g. per liter.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
• Electroplating And Plating Baths Therefor (AREA)

Applications Claiming Priority (1)

Publications (1)

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Family Applications (1)

Country Status (7)

Cited By (1)

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• 1966
  • 1966-06-10 FR FR64929A patent/FR1489213A/fr not_active Expired
• 1967
  • 1967-05-19 US US639608A patent/US3560356A/en not_active Expired - Lifetime
  • 1967-06-07 BE BE699605D patent/BE699605A/xx unknown
  • 1967-06-08 LU LU53840D patent/LU53840A1/xx unknown
  • 1967-06-09 DE DE19671621142 patent/DE1621142B2/de active Pending
  • 1967-06-09 NL NL6708030A patent/NL6708030A/xx unknown
  • 1967-06-09 GB GB26798/67A patent/GB1192461A/en not_active Expired

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