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
  • C25D11/04—Anodisation of aluminium or alloys based thereon
  • C25D11/14—Producing integrally coloured layers

Definitions

• ABSTRACT [30] Foreign Application Priority Data I M a r 5 197] ha] 21754 N71
• the present invention relates to an improvement in self-coloring anodic oxidizing process for aluminum and its alloys, an improvement that reduces the consumption of the components of the electrolytic system used and substantially eliminates precipitate formation from said system.
• the self-coloring anodic oxidizing processes so far suggested are the MS-process, based on a binary mixture of maleic acid and sulfuric acid, the MOS-process based on a ternary mixture formed of maleic acid, oxalic acid and sulfuric acid, as described in Italian Patent No. 793,929, and in Belgian Patent No. 660,867, and the TOS-process based on a ternary mixture of tartaric acid, oxalic acid and sulfuric acid, as described in Italian Patent No.
• An object of this invention is that of providing an intprovsmont in a self-coloring anodic oxidizing process for aluminum and its alloys, by which improvement the above-mentioned drawbacks are reduced.
• an object of this invention is that of providing a process that will reduce to a minimum the formation of precipitates from the electrolytic solution and consequently reduce harmful clogging phenomena in the installation and the reduction of the exchange capacity of the refrigerating apparatus and of the ion-exchanging resin columns.
• Still another object of this invention is that of reducing the consumption of the components of the electrolytic system used, also obtaining thereby an improved uniformity of the composition of the electrolytic system and, thus, a better reproduceability of the colorings obtained in the anodic coating, without having to resort to frequent and expensive additions to the electrolyte.
• the electrolytic cell is subdivided by a porous bafi'le into two compartments, an anodic one and a cathodic one, and wherein according to the improvement of this invention the electrolytic solution of the cathodic compartment is maintained at a temperature that is lower than that of the anodic compartment.
• the electrolytic solution used in the cell includes a carboxylic acid which may be selected from among the following acids: maleic, oxalic, tartaric acid, either along or in a binary or ternary combination, and generally in the presence of sulfuric acid.
• the porous baffle that subdivides the cell into two compartments, a cathodic one and an anodic one, as already described in Italian Patent No. 846,035 by the same applicant, is of a material resistant to the corrosive action of the electrolytic system used, preferably being composed of polyethylene, glass or a ceramic material.
• Said baffle has pores having a diameter comprised between 0.1 and 50;.t.
• the difference of temperature or thermal gradient between the electrolytic solutions of the two compartments, the anodic one and the cathodic one, is in general achieved by cooling down the cathodic compartment with respect to the anodic one.
• Said cooling down may be achieved by circulating a liquid coolant inside a sleeeve surrounding the cathodic compartment, or in a coil immersed in the cathodic compartment, or by means of any other equivalent suitable means.
• said coil In case a coil immersed in the cathodic compartment is used, said coil, like the porous battle, will have to be made oi. a material resisting the corrosive action of the electrolytic system used.
• a material resisting the corrosive action of the electrolytic system used Preferably, it is'rnade of the same material of which the cathode is made, e.g., of stainless steel, graphite or aluminum.
• the refrigerating system and the cathode may form one single element of the cell, the cooling coil being incorporated into the cathode itself.
• the temperature of the electrolytic solution in the cathodic compartment must be kept below 22 C.; such a temperature must be, however, higher than the temperature causing freezing of the electrolytic solution used in the cell.
• EXAMPLE 1 The anodic oxidation was carried out at 1.5 A/dm, at 20 C. and for 45 minutes, in a self-coloring bath of the MS type consisting of an aqueous solution and maleic and sulfuric acid of the following composition:

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electrolytic Production Of Metals (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=11186388

Family Applications (1)

Country Status (5)

Citations (2)

• 1972
  • 1972-03-10 NO NO00774/72*[A patent/NO130157B/no unknown
  • 1972-03-10 SE SE03052/72A patent/SE369204B/xx unknown
  • 1972-03-14 US US00234683A patent/US3775269A/en not_active Expired - Lifetime
  • 1972-03-14 AT AT213872A patent/AT311143B/de not_active IP Right Cessation
  • 1972-03-15 CA CA137,200A patent/CA1000648A/en not_active Expired

Patent Citations (2)

Non-Patent Citations (1)

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