according to the invention the metallic surfaces which are not pre - treated in the usual manner are irradiated with high - intensity nir - radiation , with a wavelength generally in the range from 730 to 1200 nm ( near infrared ). the irradiation can take place with an intensity of for example more than 1 w / cm 2 , preferably more than 100 w / cm 2 , and over a time period preferably ranging from 1 to 60 seconds , more preferably from 1 to 10 seconds . in general the duration of the nir - pre - treatment can be from 0 . 5 to 300 seconds . following the pre - treatment by nir - irradiation of the metal surface according to the invention , the subsequent coating with powder or liquid coating compositions can be carried out , where appropriate as a one - layer or multi - layer coating . the subsequent drying or curing of the coating layers can be carried out in the usual way by methods known in the coating industry . preferably the drying or curing process can be carried out by means of nir - radiation or uv - radiation , more preferably by means of nir - radiation . the metallic surfaces to be treated according to the invention need not be pre - treated , i . e . no conventional pre - treatment methods are required , such as for example degreasing and passivation ( for example phosphating , chromatising ). it is advantageous to clean the metal surfaces to be treated according to the invention of their mechanical impurities e . g . abrasive dust , boring and milling chippings , flash rusting or dust prior to their nir - pre - treatment . to remove such impurities , known mechanical methods e . g . brushing , vacuum or compressed air cleaning , “ sweeping ” as well as sandblasting can be used for the coarser impurities or for flash rusting . as a result of the irradiation with high - energy nir - radiation according to the invention , heating of the metal surface can occur . such heating does not have a negative influence on the subsequent powder coating process or on the application of the liquid coat layer , but in fact surprisingly results in an improved coating operation . halogen lamps , especially high - performance halogen lamps , for example , suitable for the pre - treatment step in the process according to the invention , can be used as the nir source . such radiation emitters with an emission spectrum maximum wavelength between 730 and 1200 nm are suitable . coating with thermally cross - linking as well as uv - curing powder coating compositions , or water - based or solvent - containing liquid coating compositions preferably takes place directly after the nir - pre - treatment of the metal surface . if required , it is also possible to separate in time the pre - treatment according to the invention from the subsequent coating . fundamentally , all processes are suited to the application of powder coating compositions and to the application of liquid coating compositions . with regard to the powder composition , electrostatic spray techniques as used in the known corona or tribo processes are particularly preferred . it is also possible to use other known powder application methods , for example application in the form of an aqueous dispersion or “ powder slurry ”. the liquid coating compositions can be applied on the substrate for example by the well known methods of dipping or spraying . known conventional thermally cross - linking powders can be used as the powder coating compositions . in this case thermal curing methods can be used for the subsequent curing of the powder coats , for example heating by means of convection ovens or medium wavelength infrared radiation . after the pre - treatment according to the invention , it is also possible to apply powder coating compositions that can be cured with uv - radiation . such powder coats are described for example in european patent applications ep 739922 , ep 702067 or ep 636660 . directly after the nir - pre - treatment , a uv - curing powder coat can be applied on the substrate surface and can be cured in a few seconds by uv - radiation . the residual heat of the nir - pre - treatment is sufficient to melt the uv - powder coat and to obtain the flow of the coating layer , without the input of further heat . this alternative process according to the invention creates the possibility of a powder coating process with a very low energy consumption . powder coating compositions that are suitable for being cured by means of nir - radiation can also be used . such powder coats are described for example in wo 99 / 41323 . when such powder coats are used , it is preferred to cure the powder coat layer directly after its application by irradiating it with nir - radiation . in this case according to the invention , the powder initially melts and then cures in a very short time and a distinct shortening of the curing time of the powder coats in comparison with the conventional pre - treatment can be obtained . preferably powder coating compositions are used that are suitable for being cured by means of nir - radiation or uv - radiation , more preferably by means of nir - radiation . liquid coats that can be used , for example , are water - dilutable or solvent - containing coating compositions which are commonly used and known to those skilled in the art and which can be used , for example , as single or multi - layer , coloured or colourless coatings on substrates for use as fillers , basecoats or top or clearcoats in the car industry or in the industrial coating area . after their application , they can be dried by well known methods over a longer period of time at room temperature or subjected , where appropriate after a flash - off time , to drying or curing at a higher temperature . furthermore , curing by means of high - energy radiation , for example uv - radiation , is possible . flashing off , drying or curing is also possible , for example , by means of exposure to nir - radiation . the coatings obtained by the process according to the invention , especially the powder coatings , have an excellent adherence , a good corrosion resistance and an excellent flow . coating faults such as craters , fisheyes or adherence defects that generally appear in the coating of untreated metal surfaces , can be avoided by the process according to the invention . the process for the pre - treatment of metal surfaces with nir - radiation according to the present invention permits considerable savings on investment , energy , and operating costs , waste water and waste materials . the organic impurities that are generally present on the surface , such as fat and oil residues or other impurities , for example fingerprints , are removed by the process according to the present invention , whereby the time needed for the pre - treatment ranging from 10 to 30 minutes for conventional pre - treatment methods is shortened to a few seconds . in particular , in combination with curing of coating layers by means of nir - radiation , a very high throughput for the coating is possible , especially for the powder coating . nir - pre - treatment of a steel surface and subsequent coating with nir - curing powder coat a cylindrical steel tube polluted with oils and fats resulting from its production process and from its treatment for protection against flash rusting was irradiated , while rotating , from a distance of 6 cm with a conventional nir - radiation emitter ( power 1000 w ) for 10 seconds , whereby the surface heated up to a temperature between 100 ° c . and 120 ° c . a nir - powder coat durotherm ray - tec nir - 9216 ( commercial product of dupont pulverlack gmbh & amp ; co . kg ) was applied on the surface that had been pre - treated in this way , and melted on the pre - tempered surface . a further nir - radiation emitter subsequently completely cured the powder coat layer in 8 seconds . a homogeneous flow surface resulted , free of pores and blisters , with excellent adherence to the substrate and with the following properties : a steel tube polluted with oils and fats analogous to example 1 was coated , without pre - treatment according to the invention with a nir - powder coat durotherm ray - tec nir - 9216 and subsequently irradiated , while rotating , from a distance of 6 cm with a nir - radiation emitter with a power of 1000 w for a duration of 18 seconds . during this time , melting and curing of the powder coat layer occurred . blisters developed on the surface during the melting process , craters formed due to insufficient wetting and some regions remained unwetted over large areas . testing of the coating properties provided the following results : nir - pre - treatment of a steel surface and subsequent powder lacquer coating and convection curing a steel plate polluted with oils and fats resulting from its production process and its treatment for protection against flash rusting was used . the plate was irradiated with a conventional nir - radiation emitter ( 1000 w ) from a distance of 8 cm for a duration of 12 seconds . the surface of the steel plate was thereby thermally activated and was heated superficially to a temperature of 130 ° c . the steel plate was subsequently coated with a conventional thermoreactive powder coat on a base of polyester / triglycidylisocyanurate resin / hardener system and the powder coat layer was cured in a convection oven at 200 ° c . for 15 minutes . an analysis of the coating obtained provided the following results : nir - pre - treatment of an aluminium surface and subsequent coating with a water primer an aluminium profile in an uncleaned condition for use in the window construction industry was irradiated with a nir - radiation emitter with a power of 1500 w from a distance of 5 cm and at a conveyor speed of 8 m / min . after a cooling distance of 4 m , the profile strip was coated with a conventional aqueous primer that was dried subsequently with a nir - radiation emitter with a power of 500 w from a distance of 10 cm . a pore - free coating with good adherence was obtained , the properties of which corresponded to a coating with the primer on a conventionally pre - treated support . a grey cast iron plate about 12 mm thick was irradiated from a distance of 5 cm with a nir - radiation emitter with a power of 1500 w for 10 seconds . the plate heated up superficially to a temperature of 130 ° c . the grey cast iron plate was subsequently coated with a conventional uv - curing powder coat ( uv - tec up - 023 - 9490 - 0 , commercially available from dupont pulverlack gmbh & amp ; co . kg ), melted with a conventional ir - radiation emitter and cured with a conventional uv - radiation emitter . the coating obtained was free of surface defects and showed excellent adherence on the support .