WO2009115423A1

WO2009115423A1 - Method for sublimation coating of zinc-coated metallic surfaces

Info

Publication number: WO2009115423A1
Application number: PCT/EP2009/052727
Authority: WO
Inventors: Monica Camanini; Vincenzo Galvano
Original assignee: Monica Camanini; Vincenzo Galvano
Priority date: 2008-03-19
Filing date: 2009-03-09
Publication date: 2009-09-24
Also published as: EP2271500A1; ITMI20080471A1

Abstract

A method for sublimation coating of zinc-coated metallic surfaces in general, particularly guardrails and road sign posts, consisting in performing a pretreatment for cleaning a zinc-coated metallic surface, in applying a first layer of clear paint and a second layer of colored paint in a color that is compatible with the coating, in applying in vacuum, on the second layer of paint, a film that is preprinted with the selected coating, and in heating to 180-200°C for the sublimation transfer of the coating onto the zinc-coated surface.

Description

METHOD FOR SUBLIMATION COATING OF ZINC-COATED

METALLIC SURFACES

Technical field

The present invention relates to a method for sublimation coating of zinc-coated metallic surfaces in general, particularly guardrails and road sign posts.

Background art

As is known, a technique known as sublimation is already used to coat, surfaces which provides to apply a layer of colored powder paint onto a metallic surface and to place it in an oven at a temperature of 160-180⁰C for baking. After such preliminary steps, sublimation is performed, which provides to apply a film that is preprinted with the desired coating and is kept in close contact with the surface by applying vacuum, so as to provide, in the subsequent treatment in an oven at 180-200⁰C, the transfer of the coating layer onto the surface, which by means of a heat source, by way of a chemical process, allows the inks to pass from the solid state to the gaseous state, obtaining the desired effect.

Such technique, which is used on different metallic surfaces, currently cannot be used with zinc-coated metallic surfaces, since the layer of zinc, at the sublimation temperature, tends to detach from the metallic surface, which would tend to peel and consequently damage the applied coating.

Disclosure of the invention

The aim of the present invention is to solve the problem described above, by providing a method for sublimation coating of zinc-coated metallic surfaces in general, particularly guardrails and road sign posts, which allows to obtain a finished product in which it is possible to have a uniform coating that adheres well to the treated surface.

Within this aim, an object of the invention is to provide a method which, besides allowing the application of the coating, allows to obtain an article in which the surface is better protected against external atmospheric agents, consequently increasing the useful life of the article.

Another object of the present invention is to provide a method which, thanks to its peculiar features, is capable of giving the greatest assurances of reliability and safety in use. Still another object of the present invention is to provide a method that can be easily carried out starting from commonly commercially available elements and materials.

This aim, these objects and others that will become better apparent hereinafter are achieved by a method for sublimation coating of zinc-coated metallic surfaces in general, particularly guardrails and road sign posts, characterized in that it consists in performing a pretreatment for cleaning a zinc-coated metallic surface, in applying a first layer of clear paint and a second layer of colored paint in a color that is compatible with the coating, in applying in vacuum, on said second layer of paint, a film that is preprinted with the selected coating, and in heating to 180-200⁰C for the sublimation transfer of said coating onto said zinc-coated surface.

Further characteristics and advantages of the present invention will become better apparent from a preferred but not exclusive embodiment of a method for sublimation coating of zinc-coated metallic surfaces in general, particularly guardrails and road sign posts, provided in the foregoing description.

Ways of carrying out the invention

Generally the method provides first of all the execution of a cleaning pretreatment that can be performed in different ways. A first way of execution provides for sandblasting, by means of sandblasting machines that use shot of different particle sizes fired by appropriately provided turbines at an adjustable speed, so as to remove from the surface any impurity left by zinc or other slag, thus obtaining a smooth and uniform external surface. It is particularly important that sandblasting rounds the pointed drips of zinc coating, which in the subsequent steps of operation could have damaged the film used for sublimation.

Moreover, the sandblasting operation facilitates the adhesion of the layers of paint, making separation of the paint impossible. The shot can vary depending on the residues on the surface and the shot that is used can be made of fine, coarse, sharp, rounded steel or ceramic shot of different shapes and sizes, and other types of shot that must be selected according to the state of the zinc-coated steel.

Once the sand treatment step has ended, elimination of dust is performed.

Pretreatment can also be performed by means of an alkaline liquid that is applied by spraying in combination with a degreasing additive in an aqueous solution.

According to an embodiment that must not be understood in a limiting sense, it is possible to use an alkaline liquid of the type known commercially by the trademark Gardoclean-IS 2410^®, which is applied for a period ranging from 2 to 3 minutes, with a bath temperature ranging from 50 to 70⁰C and with a product concentration ranging from 20 to 50 grams per liter. Once the treatment has been performed with the methods typical of the situation, it is possible to proceed with rinsing and subsequent drying.

If needed, after alkaline washing it is possible to perform a further treatment, commonly known as "T- wash", which consists of a chemical treatment that is intended to convert the surface zinc into zinc phosphate. A different type of pretreatment can be obtained by performing washing with an acid liquid in an aqueous solution applied by spraying or agitation. The acid liquid can be constituted by GARDOCLEAN 61 ^®, applied by spraying with a treatment time ranging from 5 to 10 minutes, with a temperature ranging from 50 to 70⁰C and with a bath concentration ranging from 50 to 150 grams per liter. It is optionally possible to apply the aqueous solution by ultrasound with a treatment time ranging from 5 to 30 seconds, with a bath temperature ranging from 50 to 60⁰C and with a concentration ranging from 50 to 100 grams per liter. Once washing has been performed, the usual rinsing and drying steps are performed.

As a pretreatment, it is also possible to use the application of steam, which is performed after cleaning with a rigid brush the surface to be treated, sending a jet of high-pressure steam to remove the residue parts. In particular, cleaning of the large nonuniform residues of zinc is performed by means of metallic brushes that rotate or roll on the surface. Then any impurity is cleaned in depth and subsequently the jet of high- pressure steam is applied in order to remove all the residues left on the surface, which is then dried. After performing the cleaning pretreatment operation, a first layer of clear insulating paint is applied in the form of an epoxy powder, so as to create a layer that provides protection also against external agents.

Once the first layer of paint has been applied, the article is heated in an oven at temperatures ranging from 160 to 180⁰C. After the first layer of clear paint, a second layer of colored paint, in a color that is compatible with the final coating layer, is applied; in this case also, an epoxy paint is used which has the advantage of anchoring well to the first layer of paint and has a color that is compatible with the coating layer used. The second layer also is baked in an oven at a temperature ranging from 160 to 180⁰C.

Once the two layers have been applied, the final step is performed, applying a film that is preprinted with the required coating.

The preprinted film is made to adhere by vacuum intimately to the surface, and the entire assembly is inserted in an oven at 180-200⁰C, so as to create an effect that causes the transition of the inks from the solid state to the gaseous state by means of a heat source.

Considering, by way of non-limiting example, the case of guardrails, the coating advantageously has a wood-like pattern, which lends itself well to "camouflage" of road guardrails, providing a more environmentally friendly image, while having a high resistance even against atmospheric agents.

From what has been described above it is evident that the invention achieves the proposed aim and objects, and in particular the fact is stressed that the method used has the peculiarity of providing first of all a pretreatment operation that makes the surface uniform and prevents any slag or impurities from damaging the preprinted film by disrupting the vacuum effect.

Moreover, the use of a layer of clear paint in practice creates a binder, which provides a barrier that prevents the surface on which the hot zinc- coating has been applied from being damaged or from cracking during the steps for treatment in the oven, thus obtaining an article which, besides having great stability, is better protected against atmospheric agents in general. The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims.

All the details may further be replaced with other technically equivalent elements. In practice, the materials used, so long as they are compatible with the specific use, may be any according to requirements.

The disclosures in Italian Patent Application No. MI2008A000471 from which this application claims priority are incorporated herein by reference.

Claims

CLAIMS 1. A method for sublimation coating of zinc-coated metallic surfaces in general, particularly guardrails and road sign posts, characterized in that it consists in performing a pretreatment for cleaning a zinc-coated metallic surface, in applying a first layer of clear paint and a second layer of colored paint in a color that is compatible with the coating, in applying in vacuum, on said second layer of paint, a film that is preprinted with the selected coating, and in heating to 180-200⁰C for the sublimation transfer of said coating onto said zinc-coated surface.

2. The method according to claim 1, characterized in that said cleaning pretreatment is performed by sandblasting.

3. The method according to claim 2, characterized in that said cleaning pretreatment performed by sandblasting is obtained by means of sandblasting machines that fire shot of different particle sizes.

4. The method according to claim 1, characterized in that said cleaning pretreatment is performed by means of an alkaline liquid.

5. The method according to claim 4, characterized in that a chemical treatment is performed after treatment with alkaline liquid in order to convert the surface zinc to zinc phosphate.

6. The method according to claim 1, characterized in that said cleaning treatment is performed with an acid liquid.

7. The method according to claim 6, characterized in that said acid liquid is applied by spraying.

8. The method according to claim 6, characterized in that it is performed by immersion in an aqueous solution with acid liquid with the application of ultrasound.

9. The method according to one or more of the preceding claims, characterized in that said cleaning pretreatment is performed by applying steam, after cleaning with a rigid brush the surface to be treated by sending a jet of high-pressure steam to remove the residue parts.

10. The method according to claim 1, characterized in that said first layer of clear paint is provided by means of epoxy paint.

11. The method according to claim 10, characterized in that said epoxy paint is in powder form.

12. The method according to one or more of the preceding claims, characterized in that the article is subjected, after the application of said first layer of paint, to baking in an oven at a temperature ranging from 160 to 180⁰C.

13. The method according to one or more of the preceding claims, characterized in that said coating has a wood-like, marble-like, mimetic pattern, etc.

14. A manufactured article made of hot zinc-coated metallic plate, characterized in that it comprises a coating obtained by means of the method according to the preceding claims.