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
  • C25D11/30—Anodisation of magnesium or alloys based thereon
• • 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
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D9/00—Electrolytic coating other than with metals
  • C25D9/04—Electrolytic coating other than with metals with inorganic materials
  • C25D9/06—Electrolytic coating other than with metals with inorganic materials by anodic processes

Definitions

• an electric current is set up which ceases 'if the electric connection is broken.
• the system functions as a primary cell, and one obtains in this way, the aforementioned excellent coating so highly resistant to corrosion.
• the new invention consequently consists in immersing the metallic object to be protected, after suitable degreasing and pickling, in a bath containing ions wholly or partially constituted of for example be composed of a magnesium-base metal, is then electrically connected, as explained above, to a second electrode composed of a more noble metal or element, such for instance as lead,
• a galvanic current is at on-ce'set up, accompanied by a deposit of an oxide of manganese on the magnesium base electrode.” Ashas been stated, this coating is particularly resistant to corrosion.
• Ifrne manganese maybe present inlthe bath either in theformnfmanganeseions formed by the dissociation of a manganous salt, or in the form of manganate or permanganate ions. It is 1 manganese.
• the said metallic object which may 2 particularly advantageous that the ion containing the elementmanganes e should be associated with"chr"omate or bichr'omate ions, agrar anstance in MnCreOi.
• the Coating is fdlm d Of all bldde OI OXi dS Qf manganese, whichmay also beassdciat'e'd with an oxide of metals whdseichs are present together with manganese i'nth bath.
• Example 1 A piece of sheet composed of a magnesium alloy containing 1.5% manganese, is cleaned mechanically and immersed for one hour in a 1% solution of KMnOr, and at the same time connected electrically to a second electrode of carbon. The temperature of the solution is maintained at 60 C. One obtains a light brown film of an oxide of manganese.
• Example 2 An object composed of a magnesium-alloy containing 3% Al and 1% Zn which object has been forged, is pickled in a solution of chromic acid and immersed at room temperature for 4 hours in a solution of MnCrzOv, and at the same time connected electrically to a second electrode of carbon.
• the film contains an oxide of manganese together with an oxide of chromium.
• Example 3 A cast object composed of magnesium alloy containing 10% Al, is first pickled in nitric acid and then immersed for 2 hours at room temperature in a solution made by dissolving 50 grams of C1303, 10 grammes of KMnO4 and 50 grammes of MIiCOs in 1 litre of water, the said object being at the same time electrically connected to a second electrode of iron.
• the film obtained is grey.
• Example 4 An object composed of semi-mild steel, after previous picking in H2SO1, is immersed for half an hour at 40 C. in a solution obtained by dissolving 100 grammes of MnCOz in a litre of water containing 70 grammes of CrOs, the said object being at the same time connected electrically with a second electrode of lead.
• a grey film which turns black after treatment in hot paraflin.
• the coatings so formed are very adherent, and can be obtained very thick if one continues the galvanic treatment for a suificient length of time.
• the coating is moreover of substantially uniform thickness and character irrespective of the shape of the object treated. This is true even for the interior of angles or tubes in contradistinction to the well known difiiculty of obtaining uniform deposits on such parts in the case of the anodic processes of protection habitually employed. It is highly probable that this result is due to the nature of the current giving rise to the deposit, this current being galvanic and not electrolytic in origin; in other words the process itself produces the electric current necessary to form the deposit, instead of consuming an electric current extraneously produced.
• the above invention also covers as new industrial products all metallic objects, and in particular objects made of magnesium-base metals, on which coatings composed principally of an oxide of manganese have been deposited, either as such or when subsequently treated in a bath of hot parafiin or other hydrocarbon, the galvanic baths serving to put the said invention into effect and the protective coating itself so obtained.
• a process for protecting metallic objects composed of a substance selected from the group consisting of magnesium and alloys containing magnesium as their major constituents by making the object to be protected the anode, in a galvanic battery having a cathode more noble than magnesium and having an electrolyte consisting essentially of an aqueous solution of at least one compound selected from the group consisting of manganates, permanganates and mananese bichromate, electrically connecting said anode and said cathode outside said bath, and allowing a galvanic current to flow, in said solution, from said anode to said cathode until a protective film of substantial thickness is formed on said anode, removing said anode from said solution and washing same, all without supplying any electric current from the outside of said galvanic cell.
• electrolyte is an aqueous solution made by adding 50 gr. MnCOa, 50 gr. ClOs and 10 gr. KMnO4 to each liter of water.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Prevention Of Electric Corrosion (AREA)
• Electroplating And Plating Baths Therefor (AREA)
• Testing Resistance To Weather, Investigating Materials By Mechanical Methods (AREA)
• Investigating And Analyzing Materials By Characteristic Methods (AREA)
• Chemical Treatment Of Metals (AREA)

Applications Claiming Priority (3)

Publications (1)

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Citations (12)

Family Cites Families (4)

• 0
  • NL NL56619D patent/NL56619C/xx active
  • BE BE467056D patent/BE467056A/xx unknown
  • BE BE466876D patent/BE466876A/xx unknown
  • BE BE437650D patent/BE437650A/xx unknown
  • NL NL67329D patent/NL67329C/xx active
• 1939
  • 1939-01-31 FR FR855683D patent/FR855683A/fr not_active Expired
• 1940
  • 1940-01-09 GB GB487/40A patent/GB593512A/en not_active Expired
  • 1940-01-17 US US314349A patent/US2463483A/en not_active Expired - Lifetime
  • 1940-01-18 CH CH221023D patent/CH221023A/fr unknown
• 1942
  • 1942-06-09 DE DEF91923D patent/DE763283C/de not_active Expired
• 1945
  • 1945-07-26 FR FR54022D patent/FR54022E/fr not_active Expired
  • 1945-08-07 FR FR54113D patent/FR54113E/fr not_active Expired
• 1946
  • 1946-04-18 US US663248A patent/US2553449A/en not_active Expired - Lifetime
  • 1946-06-12 CH CH260236D patent/CH260236A/fr unknown
  • 1946-06-21 GB GB18691/46A patent/GB631237A/en not_active Expired
  • 1946-07-12 US US683152A patent/US2605217A/en not_active Expired - Lifetime
  • 1946-07-16 CH CH259827D patent/CH259827A/fr unknown

Patent Citations (12)

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