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
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
  • C22F1/047—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with magnesium as the next major constituent
• • 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
  • C25D11/024—Anodisation under pulsed or modulated current or potential
• • 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
• • 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
  • C25D11/06—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used
  • C25D11/08—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used containing inorganic acids

Definitions

• the present invention relates to a process for the production of magnesium containing aluminium alloys, in particular magnesium containing rolled aluminium strip or web material.
• the surface of rolled aluminium strip has excess rolling lubricants and therefore needs to be thoroughly cleaned to provide sufficient adhesion for different types of adhesives or coatings needed to withstand specified use under different and often aggressive environmental conditions.
• Multi Layer Tube/pipe A standard design of these products comprises an inner tube of a poly ethylene (PE / PEX) or other polymer and where tie resin or adhesive is provided on the polymer tube.
• PE / PEX poly ethylene
• An aluminium tube is roll formed around the inner polymer tube and welded. The adhesive secures the roll formed aluminium tube to the polymer tube.
• the aluminium tube is in turn provided with a new layer of tie resin or adhesive prior to the extrusion of the outer polymer (PE or PEX and others)
• degreased material The standard process steps related to the production of aluminium sheet materials are by rolling and annealing thereafter chemical degreasing prior to subsequent coating with a lacquer or other organic or inorganic coating.
• magnesium oxide on the surface of aluminium in MLT and other applications give bad adhesion for the adhesive on the aluminium surface.
• the magnesium oxide when exposed to moisture, the magnesium oxide is converted to magnesium hydroxide which is a mild alkali and which can attack the metal underneath a coating, resulting in the loss of adhesion.
• Magnesium containing aluminium alloys in particular magnesium containing rolled aluminium strip or web material forming basis for the process according to the invention have high strenght and at the same time give excellent forming properties.
• the skilled person would have to choose higher alloyed aluminium if he wants to down gauge the metal and maintain the strength of the product.
• the process according to the invention is based on production of magnesium containing aluminium alloy sheet material of the above kind including the following steps: I. Rolling to final thickness of the aluminium web
• electrochemical degreasing including following rinsing and drying.
• the electrochemical degreasing is done by alternating current (AC) in hot sulphuric acid resulting in a very thin aluminium oxide on the surface, typical 10 - 30nm.
• AC alternating current
• aluminium oxide is built at the aluminium - aluminium oxide interface.
• the aluminium web is generating hydrogen gas on the surface and debris and lubricants are flushed off and at the same time the aluminium oxide on the surface is chemically dissolved in the hot sulphuric acid.
• Thin oxide layer is obtained by using sulphuric acid at a concentration of 150 +/- 50 g /litre, current density of preferably 300 - 430 A/m 2 , with a contact time of 1 - 10 seconds, prefrablyl .5 - 3.5 seconds and at a temperature of 60 - 90 °C, preferably 75 - 85 °C.
• This oxide is thick enough to stop magnesium from migrating to the surface during soft annealing, but will in stead concentrate at the interface between aluminium oxide layer and aluminium metal.
• the hereby degreased material give excellent adhesion since there is no magnesium oxide on the surface
• Tests were performed with aluminium 3005 alloy sheet substrates with typically 0,5% Mg, comparing chemical degreasing with electrochemical degreasing according to the present invention prior to annealing.
• the chemical degreasing was accomplished by dipping the specimen of the sheet substrate in acid degreasing bath of sulphuric acid and hydrofluoric acid with addition of surfactants.
• electrochemical degreasing according to the invention was done by production equipment with the following parameters, current density 346 A/m2, contact time 6,4 seconds and 150g/ litre sulphuric acid with a temperature of 80°C.
• the surface of electrochemical degreased AA3005 is aluminium oxide (Oxygen peaks at the surface) and the magnesium peak is at the interface between the aluminium oxide and the aluminium metal.
• the surface of the chemically degreased material has magnesium oxide on the outer surface seen by the magnesium peak at the outermost surface.

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• Chemical & Material Sciences (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Metallurgy (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Mechanical Engineering (AREA)
• Inorganic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)

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Citations (7)

• 2010
  • 2010-11-11 NO NO10830248A patent/NO2499272T3/no unknown
  • 2010-11-11 EP EP10830248.0A patent/EP2499272B1/en active Active
  • 2010-11-11 WO PCT/NO2010/000410 patent/WO2011059341A1/en not_active Ceased

Patent Citations (7)

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