SE503304C2 - Method of surface treatment of metal objects - Google Patents

Abstract

Method for surface treatment of metal objects, including applying a coating layer (13, 16) on at least one first metal surface (8, 9, 10) which is to be given a surface treatment which is different from another metal surface (11, 12) of the object. Said first and second metal surfaces (8-12) are surface-treated by means of applying at least one totally covering coating layer (13-16) over both metal surfaces, and said second metal surface (11, 12) is subjected to subsequent machining for removal of said coating layer.

Description

15 20 25 30 35 503 304 2 quality between surfaces to be given different surface treatment, without extensive finishing work.

Said object is achieved by means of a method according to the present invention, the features of which appear from the appended claim 1.

DESCRIPTION OF THE DRAWINGS The invention will be described in more detail below with an exemplary embodiment with reference to the accompanying drawings, in which Figs. 1 and 2 show an example of the application of the method according to the invention in surface treatment of two parts of an object.

PREFERRED EMBODIMENT: Figs. 1 and 2 show parts 1, 2 of an object of castings, for example aluminum, which are to be assembled together to form a unit in the finished product. The parts 1, 2 have surfaces 3, 4, 5 which, after completion of the surface treatment, must remain coated with paint layers and surfaces 6, 7 which form mounting surfaces intended to be connected to each other in the mounted condition of the finished product.

The surfaces that are to remain coated in the finished condition consist partly of outer surfaces 3, 5, which must meet high requirements for decorative finish, corrosion-protective properties and be easily cleanable and partly of more or less non-visible surfaces 4, in the example shown a cavity, e.g. in the form of a bore, etc., which in the first instance must meet high requirements for corrosion-protective properties and easy cleanability.

In order to achieve a highly even and maximally covering surface coating of both outer surfaces 3, 5 and cavities 4 are used. According to an advantageous embodiment, surface coating by dipping the parts of the object, 1, 2 in powder coating, which can be applied in relatively thick layers and enables a good working environment. Powder coatings, however, require a well-prepared preparation, preferably by subjecting all metal surfaces 8-12 of the object parts 1, 2 after a mechanical pre-treatment of the metal surfaces to remove rust and other surface contaminants, by applying an inorganic surface. chromate or phosphate type surface converters.

After the application of the surface conversion agent, which takes place, for example, by dipping, whereby all metal surfaces 8-12 of the parts 1, 2 of the objects are treated, more specifically both the metal surfaces 8, 9, which in the finished product are to be turned outwards, as the metal surfaces 10 , which delimits cavities 4, as well as the metal surfaces 11, 12 which are to form mounting surfaces 6, 7 in the finished product.

All surfaces treated with surface conversion agents are provided in a separate application step with a basic preservative, so-called primer, which is conveniently done by dipping application to one or more primer layers 13, 14.

After application of the primer layers and subsequent drying, at least one layer of powder coating 15, 16 is applied over the same surfaces as chromated and primed with primer, which is also advantageously done by dipping, whereby all surfaces exposed to dipping, including cavity surfaces, receive good coverage. with the desired layer thickness.

The applied powder coating is oven cured, after which cooling takes place.

According to the invention, no masking of the surfaces which in the final condition are not to be coated by means of primer or varnish layer takes place, but these surfaces, i.e. the mounting surfaces 11, 12 are exposed after completion of the above-described layer application for mechanical machining to remove all coating layers on the mounting surfaces down to clean metal surface 11, 12. The machining takes place, for example, by grinding.

After the mechanical processing, the mounting surfaces 11, 12 are subjected to a renewed surface conversion by means of inorganic surface conversion agent of chromate or phosphate type in order to give the surfaces a chemical corrosion protection. Since the surfaces are not subjected to mechanical action, such as blows, etc., no primer or painting is required, which cannot exhibit the surface finish required in mounting surfaces, where in many cases a sealing contact, possibly with intermediate gasket, is required. Examples of the need for a sealing abutment are abutment between housing parts, engine parts or the like.

Example: In summary, the various steps will be described below in an advantageous embodiment using the surface treatment method according to the present invention: 1. Blasting with Algh. 0.2-1.2 mm. 2. Washing with liquid. 3. Surface transformation, for example chromating. 4. Washing with liquid. 5. Drying. 6. Chromating. 7. Application of primer 10-100 pm. 10 15 20 503 304 8. Drying. 9. Powder coating. 50-800 μm in one layer. 10. Oven hardening alt. air curing. 11. Any cooling. 12. Mechanical processing, e.g. milling of certain surfaces down to metal pure. 13. Renewed chromating of machined surfaces.

The invention is not limited to the embodiments described above and shown in the drawing, but can be varied within the scope of the appended claims. For example, one or more of the surface treatment steps may be omitted, however, at least one. surface coating layers are applied to at least two of the surfaces of the article and the coating layer in a subsequent step is removed from one surface by mechanical machining.

Claims (6)

10 15 20 25 30 35 503 304 Patent claims Method for surface treatment of metal objects, including application of coating layers (13-16) to at least a first metal surface (8, 9, 10), which is to be given a surface treatment separate from a second metal surface (II, 12) of the object, characterized in that said first and second metal surfaces (8-12) are surface treated by applying at least one coating layer (13-16) covering both metal surfaces in the form of paint and that said second metal surface (II, 12) is exposed for a subsequent mechanical processing to remove said coating layer, while said coating layer on said first metal surface is permanent. 2. A method according to claim 1, characterized in that after removal of said coating layer (13, 14, 15, 16) a surface conversion layer deviating from the first-mentioned coating layer is applied to said second metal surface (11, 12). . 3. A method according to claim 1, characterized in that said first coating layer (15, 16) is applied in the form of a powder coating. 4. A method according to claim 3, characterized in that said powder coating is applied by dipping the metal object. 5. A method according to claim 2, characterized in that the application of said deviating surface treatment layer consists in the application of an inorganic chemical surface conversion agent, for example viscromating. Method according to claim 1, characterized by the steps: blasting, chromating of all metal surfaces (8-12), application of at least one layer (13, 14) of primer to all metal surfaces, application of at least one layer (15, 16) of powder coating on all metal surfaces, mechanical processing of said second metal surface (ll-12) in order to remove all applied coating layers (13-16) and renewed chromating on said mechanically machined surface.