Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/34—Anodisation of metals or alloys not provided for in groups C25D11/04 - C25D11/32
• • 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
  • C25D5/48—After-treatment of electroplated surfaces

Definitions

• This invention relates to the oxidation and coloration of ferrous surfaces, and has for its object to provide an improved process for this purpose.
• N 0. 106,774 (No. 16582 of 1916) a process for bronzing or coloring ferrous surfaces is described, according to which the surface to be bronzed or colored is electrolytically coated with iron from an electrolyte which is a hot dense alkaline solution (for example, having a temperature of about 120- 140 C.
• the improved process for the oxidation and coloration of ferrous surfaces comprises submitting the surface to anodic oxidation only in a hot concentrated alkaline bath, for example, a concentrated solution of caustic soda.
• a hot concentrated alkaline bath for example, a concentrated solution of caustic soda.
• concentration of the bath and the temperature may vary within certain limits, but preferably, the concentration 1s such that the bath-boils between about 135- 180 0.
• Organic or inorganic oxidizing agents may be added to the bath as desired and as suitable agents of the kind may be men tioned alkali nitrates and chlorates. For example, from 10-20 per cent. of sodium nitrate may be added to the bath.
• the current density may vary within wide limits, the particular density employed depending upon the effect desired, the nature Specification of Letters Patent.
• a solution of caustic soda is prepared, of such concent ation that it boils at about 160 C.
• This solution is brought to a temperature of l45-155 C. and the object to be colored is immersed and made to serve as anode, while a current of 10 amperes per square de'cimeter is passed through. the solution.
• the surface becomes colored a violet-blue. This takes place within a few seconds if the object be small; for larger obects a correspondingly longer period of treatment is required, that is until the ob- ]ect has reached the temperature of the bath.
• a solution of caustic soda which boils at about 170 is made up.
• a steel object is submitted to anodic oxidation in this solution, under a current density of from 10-15 amperes, the temperature being about 160- 165", until a bronze coloration is obtained, the precise time required for this effect to be produced depending upon the size of the object for the reason stated in the preceding example.
• the particular effect obtained depends upon the conditions of working, such as the composition of the bath, period of immersion, the current densit and to a lesser degree upon the nature of the surface under treatment, but in any given case a simple preliminary experiment suffices to determine the factors necessary to attain the desired result. In every case time must be allowed for the object to attain the temperature of the bath.
• the current may be passed while the object is being heated up by thebath or after the object has reached the required temperature.
• the herein described process for oxidizing a ferrous surface which comprises immersing the surface in a solution of alkali of such concentration as to boil at a temperature of at least 135 C and submitting the surface to direct anodic oxidation at a temperature above 130 C.
• the herein described process for oxidizing a ferrous surface which comprises immersing the surface in a solution of caustic alkali of such concentration as to'boil at a temperature of at least 135 C. and submitting the surface to direct anodic oxidation at a temperature above 130 C.
• the herein described process for oxidizing a ferrous surface which comprises immersing the surface in a solution of caustic alkali of such concentration as to boil at a temperature of at least 135 C. and submitting the surface to direct anodic oxidation at a temperature above 130 C. under a current density of 10-15 amperes per square decimeter of the surface.
• the herein described process for oxidizing a ferrous surface which comprises immersing the surface in a solution of caustic alkali of such concentration as to boil at a temperature between 16017 0 C. and submitting the surface to direct anodic oxidation at a temperature of 145-155 C.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Treatment Of Metals (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)
• Electroplating And Plating Baths Therefor (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=11104280

Family Applications (1)

Country Status (6)

Cited By (3)

• 0
  • GB GB106774D patent/GB106774A/en not_active Expired
  • NL NL7462D patent/NL7462C/xx active
• 1916
  • 1916-11-13 FR FR483436A patent/FR483436A/fr not_active Expired
• 1919
  • 1919-09-12 DK DK29680D patent/DK29680C/da active
  • 1919-09-17 DE DE1919349227D patent/DE349227C/de not_active Expired
• 1920
  • 1920-03-15 FR FR22850A patent/FR22850E/fr not_active Expired
  • 1920-07-02 DE DE1920349228D patent/DE349228C/de not_active Expired
  • 1920-07-02 DE DE1920R0050555 patent/DE356079C/de not_active Expired
  • 1920-08-24 US US405599A patent/US1386076A/en not_active Expired - Lifetime

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