FI107376B - Method for coating metal parts and metal product coated by the method - Google Patents

Description

107376

A method for coating metal parts and a metal product coated by the method. - Förfarande för beläggning av metalldelar ooh metallprodukt belagd med förfarandet.

The invention relates to a method of coating metal parts or metal structures consisting essentially of assembled metal wires, wherein the outer coating is electrostatically applied by spraying a hot-cure powder based on a polyester resin, an epoxy resin or a mixture of the two, and the outer coating is polymerized thereafter.

The addition of such a coating has the particular function of improving the aesthetic appearance of the corresponding parts and ensuring their protection against the risk of corrosion. For this dual purpose, it is customary to provide such a coating on many metal parts or structures, for example supermarket carts, carriers, shelf elements ..... The application of the coating thus obtained is accomplished by spraying a curing powder with an electrostatic spray gun, each oven being heated to about 220 ° C to ensure polymerization of the coating.

*! However, the coating thus made has the disadvantage of inadequate resistance to impact as well as wear. This is a particularly troublesome disadvantage when such coating is applied to objects that may be subject to impact or friction, such as in supermarket carts, carrier baskets, etc.

• · * 25 In addition, this type of coating has insufficient resistance to corrosion risks when exposed to chemical products or even simply. ···. under the influence of air substances.

For the above reasons, it is an object of the present invention to provide a method for coating metal parts or structures which is such as to significantly improve the adhesion of the type of coating in question and, consequently, its impact resistance. and wear.

2 107376 For this purpose, this process is characterized in that, prior to spraying said powder, the process comprises: a) applying a zinc coating to a metal part or structure by an electrolytic process; B) applying a layer of acrylic paint to the zinc coating; and c) drying the acrylic paint layer by heat treating or polymerizing said paint layer to provide an acrylic coating intermediate layer which acts as a binding sublayer between said metallic parts and said outer coating and onto which said powder 10 is sprayed.

According to other features of the invention, there is provided: - a coating thickness of from 2 to 30 micrometers, and preferably from 5 to 25 to 15 micrometers, - application of an acrylic paint layer by dipping the parts into said paint, - application of an acrylic paint layer by spraying, - the polymerization of the acrylic paint is carried out in an oven.

It is a further object of the invention to provide a metal product, in particular a wire assembled product which is coated by a coating process.

25 •: .. j The undercoat coating not only has the advantage of ensuring a very strong bond of the outer coating to the metal part but also * * * also significantly improves the durability of the outer coating. <· «. shocks and wear. This is due in particular to the fact that:] 30 this intermediate layer, which is clearly not as hard as the zinc plated metal *; · *. alone, in a way, acts as a damping layer between the outer coating and the metal support. Thus, in the event of an impact, the outer coating may more easily withstand the risks of cracking, cracking, or peeling occurring when such a coating is applied directly to the metal member.

In general, the advantages of the parts coated by the process of the invention are apparent in the following three points: a) Excellent resistance of the external coating to impact and wear due to the reasons set forth more broadly.

B) Very high bonding of the outer coating to the coated parts and this due to the quality of the binding of this coating to the acrylic paint interlayer, which itself forms a very strong bond with the previously zinc coated metallic parts.

15 (c) Overall very good resistance to corrosion hazards from chemical products as well as from exposure to airborne substances.

. These advantages are further demonstrated by comparative tests performed on metal parts \. 20 in three separate batches: direct application of this type of external coating, coating of parts with only previously zinc coating treatment and application of such coating to parts previously subjected to both zinc coating and acrylic coating.

! · ·. In fact, these comparative tests showed that the parts of this latter batch have very clear advantages over these different batches compared to the other two batches.

In order to use the method according to the invention, the following operations are performed sequentially: 30) · 1) The parts to be coated are initially coated with a zinc coating by an electrolytic process and this after having completed the necessary previous treatments such as pickling, degreasing, etc.

4 107376 2) Zinc coated parts are provided with an acrylic plastic coating which is performed by dipping into such paint. These parts are then transferred to an oven at about 220 ° C to ensure polymerization of the acrylic paint.

3) Thereafter, the parts to be coated receive their outer coating by spraying the coating with an electrostatic spray gun. This outer coating consists of a thermosetting powder based on a polyester resin or an epoxy resin or a mixture of two. Finally, the portions 10 are again transferred to an oven heated to about 220 ° C to ensure polymerization of this outer coating.

For example, the composition of the acrylic paint used as the interlayer may be as follows:

Butanol 13.4%

Xylene 35%

In order for the interlayer thus formed to suitably perform the task effectively. 20 sticks, has a thickness between 5 and 25 microns if the outer coating * .; The thickness itself is in the order of 50 to 200 microns.

»* * *» • ·

If the hardness of the interlayer is lower than that of the zinc plated metal, it is! ·: *. good material for sufficient bonding to prevent cracking, cracking or peeling of the coating when exposed to impact or wear.

«• ·. ** ·. The outer coating can be made from heat-curing powders, such as · · · powders marketed under the trademark "POLYDROX" by Societe

Industrielle de Voisins (69). However, this is only one example, since it is possible to use many other types of hot cure powder blends based on polyester resin or epoxy resin or a mixture of the two.

Claims (9)

A process for coating metal parts or metal structures consisting essentially of assembled metal wires, wherein the outer coating is electrostatically applied by spraying a thermosetting powder based on a polyester resin, an epoxy resin or a mixture of the two prior to subsequently polymerizing, the method of spraying said powder includes: 10 a) applying an electrolytic process to the zinc coating on the metal part or structure; b) applying the acrylic paint layer to the zinc coating; and c) drying the acrylic paint layer by heat treating or polymerizing said paint layer to provide an acrylic coating interlayer which acts as a binding sublayer between said metallic parts and said outer coating and wherein said powder is sprayed onto said lower layer. . Coating process according to Claim 1, characterized in that the acrylic paint is polymerized in an oven. • · • · t »I ....: A coating process according to claim 2, characterized in that: a) the acrylic paint intermediate coating has a thickness in the range of about 2 to 30 microns. • · · · · e · · · · · · Coating process according to claim 3, characterized in that: a) the acrylic paint intermediate coating has a thickness in the range of about 5 to 25 micrometers. • · · • · o · · · Coating process according to any one of claims 1 to 4, characterized in that: • «« ·. 30 a) Applying the acrylic paint layer by dipping the parts or structures into said paint. • · · «t · * · 6 107376 5, 107376 Coating process according to any one of claims 1 to 4, characterized in that a) the application of the acrylic paint layer is carried out by spraying. 5 7. A coated metal article having a metallic surface coated with an outer coating based on a polyester resin, an epoxy resin or a mixture of the two, characterized in that: a) the binding substrate is disposed between and adhered to said metallic surface and said outer coating; the surface and said outer coating, said lower layer comprising: 1. a zinc coating adhering to said metal surface, and 2. an acrylic paint layer adhering to said zinc coating and said outer coating. 15 A metal product according to claim 7, characterized in that a) said acrylic paint is a polymerized acrylic paint. Metal product according to claim 7 or 8, characterized in that [·. : 20 (a) said substructure is defined by the structure of the welded metal wires. «· • 4 4 · • ♦ ♦ ♦ O O O O O O O O O O O O O O O O O (((((((I I I I I I I «7 107376