The invention relates to a coating structure for protecting an object, for instance against the effects of fire. Coatings are much used in steel construction to protect steel profiles from corrosion. For this purpose the steel profiles are earthed and an electrically charged powder is atomized and attracted by the earthed profile. The steel profile is then transported through a furnace so that the powder can melt and as a result forms a sealing layer. In addition to applying a coating to prevent corrosion, such coatings can also be used to give steel profiles fire-resistant properties. It is important in support structures manufactured from steel profiles that in the case of fire the steel profiles retain a certain strength for a fixed period. The fire-resistant coating ensures that the steel beam is insulated so that the heat influences of the fire have less effect on the beam. Such a fire-resistant coating consists of a charged powder applied to the beam or the profile. When the powder is heated in the furnace, the powder will melt and react and thus provide a coating layer. At increased temperature, above the furnace temperature, for instance in the case of fire, this foamable layer also begins to foam so that a porous coating layer is created. The fire-resistant coating layer then comprises small gas inclusions because the coating layer has foamed, and these gas inclusions provide for an increased insulating value, whereby the steel profile is better protected from heat influences and remains at a

lower temperature, whereby the steel profile withstands a fire for longer.

The drawback of foamable fire-resistant coatings is that profiles provided with such a coating are less readily stackable than steel profiles provided with a different type of coating. The fire-resistant coating tends to crumble easily, thereby diminishing the fire-resistant property.

It is now an object of the invention to provide a coating structure which alleviates or even prevents the above stated drawbacks.

This object is achieved according to the invention by a coating structure which comprises:

- a fire-resistant layer of a foamable powder coating; and

- a non-foamable powder coating layer which covers the fire-resistant layer.

The fire-resistant layer of foamed powder forms the desired fire resistance. The non-foamed powder layer which covers the fire-resistant layer forms a solid, non-porous layer, whereby the strength of the coating structure is improved compared to a single fire-resistant layer. Products are hereby more readily stackable without the fire-resistant layer being adversely affected. It is moreover found that with such a structure the fire resistance is considerably increased by up to even 25% compared to a single fire-resistant layer. Tests have shown that in a fire the non-foamable powder layer continues to cover the fire-resistant layer which foams in such a case. This non-foamable powder layer also stretches, whereby a proportionally very thick, mainly gas-filled layer is formed which acts as insulation layer. The covering layer moreover ensures that the foam is not directly affected by

the fire, thereby increasing the duration of fire resistance. The non-foamable powder layer preferably comprises a high-temperature powder layer, although an epoxy polyester is also effective. Such a powder layer is a hard layer.

In a preferred embodiment of the coating structure according to the invention the fire-resistant layer is applied to a second non-foamable powder layer, which powder layer is applied directly to the object. The second non- foamable powder layer here forms a base layer which improves the adhesion between the object and the fire- resistant layer. The connection between the powder of a fire-resistant layer and steel is less good, possibly due to the foamed structure, than the adhesion of a non- foamable powder layer to the surface of the object. By now providing an adhesive layer of non-foamable powder this layer continues to adhere better after foaming because of for instance fire, this being referred to as "stickability". In yet another embodiment of the coating structure according to the invention there is applied to the non- foamable powder layer covering the fire-resistant layer a second fire-resistant layer which is covered by a third non-foamable powder layer. The fire resistance is considerably improved with this structure since the intermediate layer, the non-foamable powder layer, does not reach the degeneration temperature.

The non-foamable powder layer preferably comprises a thermoset, such as an epoxy polyester or polyester. The foamable layer herein comprises a thermoplastic or thermoset, in addition to a foaming agent such as for instance zinc phosphate. This layer is applied in a powder form and melted at about 180 ^° C/200 ^° C on the object to a

hard layer. At higher temperatures which occur for instance during fire the foaming agent will begin to foam and thus ensure that a foamable layer results which provides the required insulation. The thermoset layer, such as for instance epoxy polyester, has the property of not degenerating at temperatures below 600 ^° C. Particularly in the embodiment with two foamable layers the first foamable layer will ensure that the epoxy polyester layer located thereunder is not subjected to temperatures above 600 ^° C, with the result that a very fire-resistant coating layer structure results .

The invention further comprises a combination of an object, such as a steel beam, and a coating structure according to the invention, wherein the following layers are applied successively to the surface of the object:

- fire-resistant layer of a foamable powder;

- non-foamable powder layer.

The invention also comprises a combination of an object, such as a steel beam, and a coating structure according to the invention, wherein the following layers are applied successively to the surface of the object:

- non-foamable powder layer;

- fire-resistant layer of a foamed powder;

- non-foamable powder layer. These and other features of the invention are further elucidated with reference to the accompanying figures .

Figure 1 shows a cross-sectional view of an embodiment of a coating structure according to the invention.

Figure 2 shows a time-temperature graph of a first fire resistance test (F30) .

Figure 3 shows a time-temperature graph of a second fire resistance test (FβO) .

Figure 4 shows a cross-sectional view of a bolt protecting construction. Figure 5 shows the protective construction of figure 4 arranged on a bolt connection.

Figure 1 shows a combination of an object 1 and a coating structure 2. Applied to the surface 3 of object 1 is a non-foamable coating layer 4 which functions as adhesive layer for the foamable fire-resistant coating layer 5. In order to prevent crumbling of the foamable fire-resistant coating layer 5, this layer is covered by means of a non-foamable coating layer 6. This latter layer moreover serves to hold the foam layer together during a fire.

With the above stated structure a fire resistance test is then carried out in accordance with the applicable European standards. A steel plate is herein provided with the relevant coating structure and the coating structure is then subjected to a standard fire. The temperature of the steel plate is measured at a number of points. Figure 2 shows the results of this test. The time t in minutes is shown here on the horizontal axis and the temperature T in degrees C of the surface of the steel plate is shown on the vertical axis. Steel loses its strength above 400 ^° C and, as this graph in figure 2 clearly shows, this steel plate with said coating structure has a fire resistance of F30. This means that at 30 minutes the temperature of the steel plate exceeds 400 ^° C. For a second test a coating structure is used as according to the coating structure of figure 1, but wherein on top of this coating structure is applied a further second foamable layer, which is then in turn covered by a

non-foamable coating layer. This plate with double coating structure is then subjected in the same manner to a standard fire, and the results thereof are shown in figure 3. It will be apparent that the fire retardance of this coating structure is about twice that of the previous coating structure. It will be apparent from figure 3 that a fire retardance of F60 will apply for this coating structure.

Figure 4 shows a cross-section of a protective construction for protecting bolt connections. Since the above stated coating structure is usually used for steel constructions which are fixed to each other by means of bolt connections, it is also essential to protect the bolt connections against fire in order to prevent these bolt connections becoming the weakest link in the construction. The protective construction 10 comprises a bowl-shaped housing 11 which can be manufactured from for instance paper, cardboard or plastic and a sealing foil 12. Liquid polyurethane 13 is present in the formed cavity. This protective construction 10 is placed onto a protruding bolt connection 14 (see figure 5) , whereby foil 12 is broken and the polyurethane comes into contact with air, whereby it begins to foam and fills the whole cavity of housing 11. The bolt connection is hereby wholly enclosed by a layer of polyurethane foam, which provides sufficient fire resistance. An additional advantage is that the bolt connection is hereby shielded and no moisture can therefore enter, whereby the bolt connection can no longer corrode. As a result cheaper galvanized bolts can be used instead of stainless steel bolts or painted bolts.