Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/78—Pretreatment of the material to be coated
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
  • B05D7/14—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to metal, e.g. car bodies
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D2350/00—Pretreatment of the substrate
  • B05D2350/30—Change of the surface
  • B05D2350/33—Roughening
  • B05D2350/38—Roughening by mechanical means

Definitions

• the present invention relates to a surface treated, corrosion protected, metal object in accordance with the preamble of appended claim 1.
• the present invention also relates to a method for treatment of a metal object for protection against corrosion in accordance with the preamble of appended claim 8.
• the basic principle which still generally applies is to seal the surfaces of the metal object by means of one or several coating layers so as to prevent the metal surfaces from coming into contact with oxidizing substances. In this regard, it is important to clean the metal surface carefully in order to remove corrosion which is already present and to achieve maximum adhesion of the coating layers.
• Organic as well as inorganic coatings, or often a combination thereof, are used as coating layers. Colour systems, plastic coatings, rust protection oil and the like are often used as organic coatings.
• inorganic coatings metal coatings made for example from zinc or nickel and surface conversion layers, for example of the phosphate or chromate type, are included.
• An often used combination of organic and inorganic coatings is one having a surface conversion layer arranged closest to the metal surface, a primer arranged outside the surface conversion layer and one or several coating layers of the laqcuer type arranged as a top layer.
• the above-mentioned cleaning of the surface is usually accomplished by means of blasting with round blasting particles, after which the surface is usually polished.
• the chosen blasting method and the subsequent polishing are intended to provide an optimal surface evenness so as to give the treated surface the best possible surface evenness after the final surface coating.
• powder paints have increased due to their good properties regarding their application, both for spray applications and immersion using electrostatic charge, which gives a very high coverage, especially for objects having a complicated shape.
• Powder paints are generally applied in relatively thick layers and may give a very high surface evenness, even on relatively rough metal surfaces.
• a further advantage is the abscence of environmentally harmful solvents.
• the powder paints which are applied by means of known treatment methods present inferior properties as regards protection against corrosion. Attempts have been made to improve this by means of primer layers of the kind which, due to environmental reasons, also lack harmful solvents and for this reason are water-soluble. Due to the relatively thick layers of the powder paints, very high mechanical demands on the underlying primer layers exist.
• the object of the present invention is to reduce the spreading of corrosion along a metal surface which is surface treated with a coating layers and to obtain a high adhesion between the coating layers and the metal surface.
• Said object is also accomplished by means of a method for corrosion protective treatment of a metal object, in accordance with the characterizing part of claim 8.
• Fig. 1 shows a partly cut-out perspective view of a surface which is mechanically surface treated according to the method of the invention, the view being greatly enlarged
• Fig. 2 also shows a greatly enlarged, partly cut-out cross-sectional view through a metal object which is completely treated by means of the method according to the invention.
• DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The perspective view according to Fig. 1 is a photo, magnified approximately 75 times, of a metal object according to the invention after a first treatment step including a mechanical pre-treatment of the metal surface 2.
• This pre-treatment comprises a profiling of the metal surface 2 to form uneven recesses 3 and sharply edged protrusions 4, by means of which a great surface enlargement in relation to a plan projection of the surface of the object is accomplished.
• the object 1 can be a sheet or a moulded object of aluminium, steel with a certain carbon rate or the like, which requires corrosion protection for technical and aesthetic reasons. If the object has a very high wall thickness, a surface treatment such as lacquering is made primarily for aesthetic reasons and in order to facilitate cleaning of the surface.
• this profiling to the above- mentioned uneven topography shown in the figures to an optimum surface enlargement degree exceeding 4 times, preferably within the interval 6-12 times, is accomplished in order to reduce the spreading of corrosion with time in an optimum way and in order to increase the adhesion of applied coating layers, without reducing the demands of a surface evenness of high quality on the outer coating layer.
• an organic coating such as a surface conversion layer 5 of e.g. phosphate or chromate type is applied, after which one or several primer layers 6, for example of the water-soluble type, is applied. After this surface conversion, washing by means of for example an alkaline liquid and subsequent drying are carried out.
• priming takes place by means of the application of one or several primer layers 6, preferably of the water-soluble type.
• the coating layer or layers 7, which is preferably in the form of powder paints is applied.
• the powder paints are for example applied by means of spraying or immersion. After hardening in an oven and subsequent cooling, the masking is removed and insufficiently treated surfaces can be touched-up by means of wet paint.
• the surface treatment process can for example be carried out according to the following.
• Powder painting 50-800 ⁇ m in one layer.
• Fig. 2 which shows a cross-section through a surface-treated object in approximately 600 times enlargement
• the breakthrough could be a crack, which means that the metal surface 2 is exposed to the surrounding corroding atmosphere, for example salt water, whereby corrosion is spread, i.e. the metal is reduced both vertically and along the metal surface.
• the major spreading of corrosion normally takes place along the metal surface 2, and it should be noted that the profiled surface according to the invention provides a sharp increase of the spreading path along the metal surface as compared with a very even surface, i.e. a surface having a very smooth surface.
• the increase in the propagation path can be expressed as a surface enlargement degree as compared with a plan projection of the metal surface or as compared with the very smooth surface 9 of the coating layer of the paint 7 through the use of modern paints, for example powder paints, and associated thick coating layers.
• a very high surface evenness can be obtained in the covering surface 9, even with a substantial profiling of the metal surface 2.
• an optimum interval has been found within which a high surface enlargement, and thereby also a long path for the spreading of the corrosion, can be obtained while still maintaining a high surface evenness in the outer surf ce 9 of the coating layer 7.
• this degree of surface enlargement is within the interval 6-12 times or exceeds at least 4 times.
• surface enlargement signifies the number of times the surface is enlarged in relation to a certain reference surface.
• the surface of the coating layer has been chosen, but alternatively a plan projection of the metal surface can thus be chosen as a reference, whereby a plane object is considered.
• a glass surface with a high degree of fineness can alternatively be regarded as a reference.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Wood Science & Technology (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Life Sciences & Earth Sciences (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Laminated Bodies (AREA)
• Chemical Treatment Of Metals (AREA)
• Other Surface Treatments For Metallic Materials (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 1994
  • 1994-07-19 SE SE9402516A patent/SE502819C2/sv not_active IP Right Cessation
• 1995
  • 1995-07-18 WO PCT/SE1995/000867 patent/WO1996002331A1/en not_active Application Discontinuation
  • 1995-07-18 AU AU30900/95A patent/AU3090095A/en not_active Abandoned
  • 1995-07-18 EP EP95926570A patent/EP0777535A1/en not_active Ceased
  • 1995-07-18 JP JP8504961A patent/JPH10506831A/ja active Pending

Non-Patent Citations (1)

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