BE1028252A1 - Method for painting semi-trailer chassis and painted semi-trailer chassis - Google Patents

Abstract

The present invention relates to a method of painting a trailer chassis comprising degreasing the trailer chassis, applying a zinc phosphate layer to the trailer chassis, flushing the chassis, electrostatic dip painting the trailer chassis and drying the trailer chassis wherein the application of a zinc phosphate layer is done by immersion in a bath with an aqueous solution, the bath being configured for immersion of a semi-trailer chassis with a maximum size of 15 800 mm x 1 500 mm x 2 700 mm and where the aqueous solution is 5 to 25 g /l zinc (Zn) and 10 to 40 g/l phosphate (P2O5). The invention also relates to a painted semi-trailer chassis comprising at least two longitudinal girders and at least two cross girders, wherein a zinc phosphate layer is applied to the chassis by immersion in a bath with an aqueous solution.

Description

PROCEDURE FOR PAINTING TRAVEL CHASSIS AND PAINTED TRAILER CHASSIS

TECHNICAL FIELD The invention relates to a method for painting a semi-trailer chassis. In a second aspect, the invention also relates to a painted chassis for a semi-trailer.

BACKGROUND ART A semi-trailer chassis is a heavily loaded part of a semi-trailer. It is exposed to highly variable weather conditions. A semi-trailer chassis is therefore susceptible to corrosion. To protect a semi-trailer chassis, the chassis is painted. Due to frequent loading and unloading, this coating is quickly damaged, causing a trailer to corrode again.

To make the chassis more resistant to corrosion, a protective layer is applied to the semi-trailer chassis under the paintwork. Such a protective layer is, for example, a zinc phosphate layer. This layer is sprayed onto the chassis, after which the zinc phosphate layer is sprayed over with a layer of lacquer.

This known method has the following drawbacks. By spraying the zinc phosphate layer, not all areas of the trailer chassis are easily accessible, for example, hollow spaces behind an opening cannot be treated. This can still cause corrosion. The corrosion becomes even worse if moisture enters these cavities. The corrosion extends and eventually affects parts of the chassis that were originally protected by the paint and zinc phosphate coating. An additional disadvantage is that by spraying a zinc phosphate layer and a paint layer, it is not possible to apply the zinc phosphate layer and paint over the complete chassis with a uniform thickness. In some accessible areas of the trailer chassis, a zinc phosphate layer and a lacquer layer have been visually applied, but this is very thin or almost missing, so that the metal of the trailer chassis is no longer protected with the slightest damage during loading and unloading. The present invention aims to find at least a solution to some of the above-mentioned problems or drawbacks.

SUMMARY OF THE INVENTION In a first aspect, the present invention relates to a method according to claim

1. The great advantage of this method is that a zinc phosphate layer is applied to the semi-trailer chassis by immersing the semi-trailer chassis in a bath with an aqueous solution. Also places that are not or are difficult to reach, such as a hollow space behind an opening, come into contact with the aqueous solution. The entire semi-trailer chassis is protected against corrosion by a zinc phosphate layer. The bath is configured for submersion of a semi-trailer chassis with a maximum size of 15 800 mm x 1 500 mm x 2 700 mm. This is sufficiently large to receive a semi-trailer chassis of a semi-trailer with a maximum allowable length of 13 600 mm. The aqueous solution contains 5 to 25 g/l zinc (Zn) and 10 to 40 g/l phosphate (P2Os), so that a sufficiently thick zinc phosphate layer is obtained for good corrosion protection. By immersion, a much more uniform thickness of the zinc phosphate layer is obtained , Weak thin spots in the zinc phosphate layer, such as when sprayed, are avoided. Preferred forms of the method are set forth in claims 2 to 9.

A specific preferred form of the invention relates to a method according to claim

5. According to this embodiment, the thickness of the zinc phosphate layer is at least 5 micrometers and at most 50 micrometers. The zinc phosphate layer is sufficiently thick for good corrosion protection and, on the other hand, also sufficiently thin to prevent the zinc phosphate layer from breaking due to mechanical forces in the semi-trailer chassis, such as static forces due to the load or dynamic forces during driving.

In a second aspect, the present invention relates to a painted semi-trailer chassis according to claim 10. This semi-trailer chassis has the advantage, inter alia, that a protective zinc phosphate layer is applied over the entire chassis, even in places that are difficult to reach.

Preferred shapes of the painted semi-trailer chassis are described in subclaims 11 to 14.

In a third aspect, the present invention relates to a painted semi-trailer chassis according to the second aspect, painted by a method according to the first aspect,

DETAILED DESCRIPTION Unless otherwise defined, all terms used in the description of the invention, including technical and scientific terms, have the meaning as generally understood by those skilled in the art of the invention. For a better assessment of the description of the invention, the following terms are explicitly explained.

“A”, “the” and “the” in this document refer to both the singular and the plural unless the context clearly dictates otherwise. For example, “a segment” means one or more than one segment. , “includes” are synonyms and are inclusive or open terms designating the presence of the following, and which do not exclude or preclude the presence of other components, features, elements, members, steps known from or described in the art.

Citing numerical intervals through the endpoints includes all integers, fractions and/or real numbers between the endpoints, including these endpoints.

In the context of this document, lacquering is the coating of a surface with lacquer, where lacquer can also be a paint or a coating.

In a first aspect, the invention relates to a method for painting a semi-trailer chassis.

According to a preferred embodiment, the method comprises the steps of degreasing the trailer chassis, applying a zinc phosphate layer to the trailer chassis, flushing the chassis, electrostatic dip painting of the trailer chassis and drying the trailer chassis.

In a preparatory step, the semi-trailer chassis is degreased. Degreasing is necessary to obtain a good adhesion of zinc phosphate to the trailer chassis. Preferably, a chemical agent for degreasing and cleaning the surface of the trailer chassis is used. The chemical agent is sprayed onto the surface of the trailer chassis and/or the trailer chassis is dipped into a bath of a chemical agent. The chemical agent is an alkaline or acidic cleaning agent, such as, for example, but not limited to sodium metasilicate and sodium hydroxide.

In a next step, a zinc phosphate layer is applied to the semi-trailer chassis.

The semi-trailer chassis is immersed in a bath containing an aqueous solution. The bath is configured for submersion of a semi-trailer chassis with a maximum size of 15 800 mm x 1 500 mm x 2 700 mm. The bath is a beam-shaped bath with a length of at least 16 000 mm, a width of at least 2 900 mm and a height of at least 1 700 mm. The bath is preferably a beam-shaped bath with a length of at least 16 000 mm, a width of at least 1 700 mm and a height of at least 2 900 mm. The last bath requires less floor space. The pool is large enough to receive a semi-trailer chassis with a maximum permitted length of 13 600 mm according to European regulations, a maximum permitted width of 2 550 mm and a typical height of the loading floor between 1 230 mm and 1 360 mm . The bath has sufficient space to receive a semi-trailer chassis, whereby the semi-trailer chassis does not touch any edges of the bath during installation and removal. The aqueous solution comprises 5 to 25 g/l of zinc (Zn), preferably 5 to 15 g/l. The aqueous solution comprises 10 to 40 g/l phosphate (P 2 O 3 ), preferably 15 to 30 g/l. In this context, an amount per liter of aqueous solution is meant. Such a solution has a sufficiently high concentration for the application of a zinc phosphate layer on the entire trailer chassis, the thickness of the zinc phosphate layer being sufficient for a good protection against corrosion. A zinc phosphate layer offers better protection against corrosion than an iron phosphate layer and is more durable. This makes a zinc phosphate layer suitable for outdoor use, which is advantageous for a semi-trailer chassis. A zinc phosphate layer is also advantageous for better adhesion of a paint during dip painting. The immersion is advantageous because also places of the semi-trailer chassis which are not or are difficult to reach, such as a hollow space behind an opening, come into contact with the aqueous solution. The entire semi-trailer chassis is protected against corrosion by a zinc phosphate layer. In addition, a much more uniform thickness of the zinc phosphate layer is obtained by dipping. Weak thin spots in the zinc phosphate layer, such as when spraying a zinc phosphate layer, are avoided.

In a later step, the electrostatic dip painting of the semi-trailer chassis follows. Electrostatic dip coating is also known as cathodic electrodeposition (CED) or as Kathodische Tauch Lackierung (KLT). The semi-trailer chassis is immersed in a bath of charged paint particles. The bath has dimensions similar to those previously described for the bath for applying the zinc phosphate layer. The trailer chassis is the cathode. The bath includes at least one anode. Due to a voltage difference between anode and cathode, the charged lacquer particles are attracted to the semi-trailer chassis. With a semi-trailer chassis with hollow spaces behind an opening, additional anodes are preferably placed near the openings. This ensures a better attraction of lacquer particles in the openings and the hollow space behind. Electrostatic dip painting is advantageous for a very uniform layer of paint, even in areas of the trailer chassis that are inaccessible or difficult, such as a hollow space behind an opening. The electrostatic dip painting ensures good adhesion of the paint to the trailer chassis.

The electrostatic dip painting allows a rapid application of a paint on a large surface such as a semi-trailer chassis. The applied paint provides additional protection of the semi-trailer chassis against corrosion. In a final step, the semi-trailer chassis is dried. Drying hardens the applied paint and forms a strong protective layer around the semi-trailer chassis.

According to one embodiment, the semi-trailer chassis is immersed in the aqueous solution for at least 1 minute and at most 5 minutes, preferably at least 2 minutes and at most 4 minutes, more preferably 3 minutes. In addition to the concentration of zinc and phosphate, the thickness of the zinc phosphate layer also depends on the duration of the immersion. Immersion in a bath within the stated time at a concentration of zinc and phosphate according to an embodiment described above is sufficient to form a zinc phosphate layer on the semi-trailer chassis which offers sufficient protection against corrosion and also has sufficient strength against damage. A shorter period of time results in a zinc phosphate layer that is too thin. With a longer period of time, the growth of the zinc phosphate layer is too slow and the thicker zinc phosphate layer is unnecessary for protection against corrosion. According to one embodiment, the temperature of the aqueous solution is at least 309 C and at most 85° C, preferably at least 40° C and at most 80° C, more preferably at least 50° C and at most 75° C. A higher temperature results in a thicker zinc phosphate layer at the same concentration of zinc and phosphate and the same duration of immersion. A temperature within this range is advantageous for obtaining a thicker zinc phosphate layer at the same concentration of zinc and phosphate and the same time period as in the embodiments described above. A temperature within this range is advantageous for obtaining an equal zinc phosphate layer at the same concentration of zinc and phosphate and a shorter period of time as in the embodiments described above. A higher temperature outside the scope of the present invention requires too much energy to heat the bath. In one embodiment, the aqueous solution comprises an accelerator. An accelerator is advantageous for speeding up the formation of the zinc phosphate layer on the trailer chassis. Non-limiting examples of suitable accelerators are nitrite ions, by addition of, for example, sodium nitrite or ammonium nitrite, chlorine ions, hydroxylamine ions, aromatic nitro compounds, in particular m-nitrobenzene sulphonate ions, hydrogen peroxide or an oxime, such as for example acetaldehyde oxime or acetoxime.

According to one embodiment, a zinc phosphate layer is obtained on the semi-trailer chassis with a thickness of at least 5 micrometers and at most 50 micrometers.

Preferably, the zinc phosphate layer is at least 15 micrometers, more preferably at least 20 micrometers, even more preferably at least 25 micrometers.

A zinc phosphate layer of at least 5 micrometers is sufficiently thick for good corrosion protection and will not be damaged immediately when loading and unloading a trailer. A zinc phosphate layer of no more than 50 micrometers is sufficiently thin to prevent mechanical forces in the trailer chassis, such as static forces due to the load or dynamic forces during driving, from breaking and flaking off the zinc phosphate layer.

According to one embodiment, the semi-trailer chassis is rinsed after degreasing and before applying the zinc phosphate layer. The trailer chassis is rinsed with water, preferably with demineralized water, to remove residues of the chemical cleaning agent. Optionally, the trailer chassis is rinsed with an aqueous acid solution to remove alkaline cleaning agents. A non-limiting example of an aqueous acid solution is a dilute nitric acid solution.

According to a further embodiment, the semi-trailer chassis is flushed twice. This is advantageous for the complete removal of residues of the chemical cleaning agent. Preferably, the first time is rinsed with an aqueous acid solution and the second time with water. It will be apparent to one skilled in the art that other combinations for flushing are possible.

According to one embodiment, an activation step is carried out before applying the zinc phosphate layer. The semi-trailer chassis is immersed in a bath containing an activator. The activator promotes the formation of fine crystalline phosphate layers on the trailer chassis. The activator creates nucleation sites on the metal surface of the trailer chassis. As a result, a zinc phosphate layer with a high density is obtained, which is advantageous for the corrosion protection. A non-limiting example of an activator is titanium phosphate.

According to one embodiment, the semi-trailer chassis is rinsed after the zinc phosphate layer has been applied. The semi-trailer chassis is rinsed with water, preferably with demineralized water. The purging is beneficial for removing unbound zinc and phosphate ions and any accelerator.

According to one embodiment, the zinc phosphate layer is passivated after application.

The semi-trailer chassis is immersed in a bath of passivation agent.

Through passivation, a very thin chromate layer is applied to the zinc phosphate layer.

The chromate layer has a thickness of at most 0.5 micrometer, preferably at most 0.3 micrometer, more preferably at most 0.1 micrometer. The chromate layer seals pores in the zinc phosphate layer and binds oxygen. This is advantageous for an improved corrosion protection by the zinc phosphate layer.

The chromate layer is additionally advantageous due to a self-repairing effect in the event of damage.

The chromate layer comprises hexavalent chromium Cr(VI). The chromate layer preferably comprises trivalent chromium Cr(III). This is advantageous due to the lower environmental impact compared to hexavalent chromium.

According to a further embodiment, the method comprises the additional step of flushing the trailer chassis after passivation.

The semi-trailer chassis is rinsed with water, preferably with demineralized water.

This is advantageous for removing excess passivation agent.

According to one embodiment, the electrostatic dip coating is carried out at a DC voltage of at least 50 V and at most 500 V, preferably at least 100 V and at most 450 V, more preferably at least 150 V and at most 400 V.

The direct voltage is preferably constant during the electrostatic dip coating.

DC voltage is advantageous for generating an electric field with constant direction field vectors.

A voltage within the specified range is sufficient to rapidly attract charged paint particles to the trailer chassis. A higher DC voltage can potentially cause breakdown between cathode and anode.

According to one embodiment, the electrical current density in the dip coating is at least 10 A/m 2 and at most 160 A/m 2 , preferably at least 15 A/m 2 and at most 140 A/m 2 , more preferably at least 20 A/m 2 . and at most 120 A/m2. A higher electrical current density provides a greater flow of charged paint particles to the trailer chassis and faster painting of the trailer chassis.

A higher current density than the indicated range is required in combination with the voltage used, as described in an earlier embodiment, for a very high electrical power with associated heavy electrical installation, which does not lead to a sufficient acceleration of the coating.

According to one embodiment, the semi-trailer chassis is dried for at least 15 minutes and at most 30 minutes, preferably for at least 20 minutes and at most 25 minutes. Within this period it is possible to completely dry out and harden a paint of a semi-trailer chassis. The period is sufficiently short for a high throughput in an apparatus for painting a trailer chassis. A hard coat of paint protects the semi-trailer chassis and the underlying zinc phosphate layer from damage after drying.

According to one embodiment, the semi-trailer chassis is dried at a temperature of at least 1509°C and at most 200°C. The high temperature results in a shorter drying time. This is advantageous, for example, to reduce the risk of dust in the coating layer and to increase the throughput in a device for painting a semi-trailer chassis. A temperature above the range of the present invention is potentially detrimental to causing cracks and/or blisters in the lacquer layer, rendering the lacquer layer undurable.

In a second aspect, the invention relates to a painted semi-trailer chassis.

According to a preferred embodiment, the painted semi-trailer chassis comprises at least two longitudinal beams and two cross beams, wherein a zinc phosphate layer is applied to the chassis by immersion in a bath of an aqueous solution, the bath being configured for immersion of a chassis with a maximum size of 15 800 mm x 1500 mm x 2 700 mm and wherein the aqueous solution comprises 5 to 25 g/l zinc (Zn) and 10 to 34 g/l phosphate (P2Os).

The pool is large enough to receive a semi-trailer chassis with a maximum permitted length of 13 600 mm according to European regulations, a maximum permitted width of 2 550 mm and a typical height of the loading floor between 1 230 mm and 1 360 mm .

The solution used has a sufficiently high concentration that the zinc phosphate layer applied to the entire trailer chassis has a thickness that is sufficient for good protection against corrosion,

The immersion is advantageous because places of the semi-trailer chassis that are not or are difficult to reach, such as a hollow space behind an opening, have also come into contact with the aqueous solution. As a result, the entire semi-trailer chassis is protected against corrosion by a zinc phosphate layer. In addition, a much more uniform thickness of the zinc phosphate layer is obtained by dipping. Weak thin spots in the zinc phosphate layer, such as when spraying a zinc phosphate layer, are absent. According to one embodiment, the zinc phosphate layer has a thickness of at least 5 micrometers and at most 50 micrometers. A zinc phosphate layer of at least 5 micrometers is sufficiently thick for good corrosion protection and will not be damaged immediately when loading and unloading a trailer. A zinc phosphate layer of no more than 50 micrometers is sufficiently thin to prevent mechanical forces in the trailer chassis, such as static forces due to the load or dynamic forces during driving, from breaking and flaking off the zinc phosphate layer. According to one embodiment, the zinc phosphate layer is passivated. Through passivation, pores in the zinc phosphate layer are sealed. This is advantageous for improved corrosion protection by the zinc phosphate layer.

According to a further embodiment, the zinc phosphate layer is passivated with trivalent chromium Cr(III). A chromate layer is also advantageous due to a self-repairing effect in the event of damage. Trivalent chromium Cr(III) is advantageous due to the lower environmental impact in comparison with hexavalent chromium. According to one embodiment, the chassis comprises a lacquer, the lacquer being applied by means of electrostatic dipping lacquers. Electrostatic dip painting is advantageous for a very uniform layer of paint, even in areas of the trailer chassis that are inaccessible or difficult, such as a hollow space behind an opening. The electrostatic dip painting ensures a good adhesion of the paint to the trailer chassis. The electrostatic dip painting allows a quick application of a paint on a large surface such as a trailer chassis. The applied paint provides additional protection of the semi-trailer chassis against corrosion.

In a third aspect, the invention relates to a painted semi-trailer chassis according to the second aspect, painted by means of a method according to the first aspect.

Claims (15)

CONCLUSIONS A method for painting a semi-trailer chassis comprising degreasing the semi-trailer chassis, applying a zinc phosphate layer to the semi-trailer chassis, rinsing the chassis, electrostatically dip painting the semi-trailer chassis and drying the semi-trailer chassis, characterized in that of a zinc phosphate layer is by immersion in a bath with an aqueous solution, the bath being configured for immersion of a semi-trailer chassis with a maximum size of 15 800 mm x 1 500 mm x 2 700 mm and where the aqueous solution is 5 to 25 g/ 1 zinc (Zn) and 10 to 40 g/l phosphate (P2Os5). Method according to Claim 1, characterized in that the semi-trailer chassis is immersed in the aqueous solution for at least 1 minute and at most 5 minutes. Process according to Claim 1 or 2, characterized in that the temperature of the aqueous solution is at least 30°C and at most 85°C. Process according to any one of the preceding claims 1-3, characterized in that the aqueous solution comprises an accelerator. Method as claimed in any of the foregoing claims 1-4, characterized in that a zinc phosphate layer is obtained on the semi-trailer chassis with a thickness of at least 5 micrometers and at most 50 micrometers. Method according to one of the preceding claims 1-5, characterized in that the electrostatic dip coating is carried out at a direct voltage of at least 50 V and at most 500 V. Method according to one of the preceding claims 1-6, characterized in that the electrical current density during the dip coating is at least 10 A/m 2 and at most 160 A/m? is. Method according to one of the preceding claims 1-7, characterized in that the semi-trailer chassis is dried for at least 15 minutes and at most 30 minutes. Method according to one of the preceding claims 1-8, characterized in that the semi-trailer chassis is dried at a temperature of at least 150 °C and at most 200 °C. 10. Painted semi-trailer chassis comprising at least two longitudinal members and at least two cross members, characterized in that a zinc phosphate layer is applied to the chassis by immersion in a bath containing an aqueous solution, the bath being configured for immersion of a chassis with a maximum size of 15 800 mm x 1 500 mm x 2 700 mm and wherein the aqueous solution comprises 5 to 25 g/l zinc (Zn) and 10 to 40 g/l phosphate (P2Os), Painted semi-trailer chassis according to Claim 10, characterized in that the zinc phosphate layer has a thickness of at least 5 micrometers and at most 50 micrometers. Painted semi-trailer chassis according to Claim 10 or 11, characterized in that the zinc phosphate layer is passivated. Painted semi-trailer chassis according to Claim 12, characterized in that the zinc phosphate layer is passivated with trivalent chromium Cr(IIT). Painted semi-trailer chassis according to one of Claims 10-13, characterized in that the chassis comprises a paint, the paint being applied by means of electrostatic dip painting. 15. Painted semi-trailer chassis according to any one of claims 10-14, painted using a method according to any one of claims 1-9.