Electronically conductive enamel composition

Abstract

A description is given of an electronically conductive enamel composition, more particularly for anti-corrosion coatings.

1 . Electronically conductive enamel composition comprising or consisting of
 (i) an enamel matrix melting at a temperature in the range 600° C. to 900° C. and   (ii) particles, embedded in the enamel matrix, of one or more electronically conductive materials, which are not noble metals, wherein the particles (ii)
 have a particle size of 700 μm or smaller 
 and are selected from the group consisting of
 (a) particles of carbon-based electronically conductive materials, 
 (b) particles of other electronically conductive materials selected from the group comprising metallic electronically conductive materials, which are not noble metals, and 
 (c) particles made up of a combination of carbon-based electronically conductive materials and other electronically conductive materials selected from the group of metallic electronically conductive materials, which are not noble metals; 
 
 and the total concentration of the particles (ii) is in the range 0.09 vol % to 67.8 vol %, preferably in the range 0.18 vol % to 67.8 vol %, more preferably in the range 1.9 vol % to 55.2 vol %, particularly preferably in the range 3.0 vol % to 44.2 vol %, with reference to the sum of the volumes of the enamel matrix (i) and the particles (ii), wherein the total concentration of particles (a) of carbon-based electronically conductive materials is 48 vol % or less with reference to the sum of the volumes of the enamel matrix (i) and the particles (a). 25 
   
     
     
         2 . Enamel composition according to  claim 1 , wherein the carbon-based electronically conductive material(s) are selected from the group consisting of graphite, graphite expandate, glassy carbon, carbon black, soot and carbon fibres. 
     
     
         3 . Enamel composition according to  claim 1 , wherein the or one, several or all of the electronically conductive material(s) has (have) a melting point in the range 600° C. to 1 800° C. 
     
     
         4 . Enamel composition according to  claim 1 , wherein the enamel matrix comprises one or more components from the group consisting of boron nitride and ground waste glass. 
     
     
         5 . Enamel composition according to  claim 1 , wherein
 (1) the composition at a voltage of 100 V has an electronic conductivity of 1*10 −13  [S/cm] or more or   (2) the composition at a voltage of 40 kV has an electronic conductivity of 1*10 −5  [S/cm] or more or   (3) both (1) and (2).   
     
     
         6 . Enamel composition according to  claim 1 , further comprising
 (i) particles of one or more stainless steel alloys embedded in the enamel matrix in a concentration of 4.2 vol % to 44.2 vol % with reference to the sum of the volumes of the enamel matrix (i) and the particles (ii) of one or more stainless steel alloys or   (ii) particles of one or more stainless steel alloys embedded in this enamel matrix and particles of one or more carbon-based electronically conductive materials embedded in this enamel matrix, wherein the total concentration of particles of the stainless steel alloys and the particles of carbon-based electronically conductive materials is 4.2 vol % to 34.5 vol %, with reference to the sum of the volumes of the enamel matrix (i) and the particles (ii), and the ratio of the volume of the particles of the stainless steel alloys to the particles of carbon-based electronically conductive materials is in the range 1:1 to 50:1, preferably 4:1 to 6:1.   
     
     
         7 . Coating comprising or consisting of an enamel composition according to  claim 1 . 
     
     
         8 . Coating comprising an enamel composition according to  claim 1  in a quantity relative to the size of the surface to be coated of 0.01 g/cm 2  to 5 g/cm 2 , and/or
 has a thickness of 10 μm to 5 000 μm, preferably of 200 μm to 500 μm. 
 
     
     
         9 . Article comprising
 a base body and   a coating according to  claim 7  disposed on the surface or a portion of the surface of the base body.   
     
     
         10 . Method for producing an article according to  claim 9  comprising:
 (1) provision of a base body, 
 (2) provision of a mixture comprising raw materials for formation of an enamel matrix (i) at a firing temperature in the range 600° C. to 900° C. and (ii) particles of one or more electronically conductive materials, which are not noble metals, wherein the particles (ii)
 have a particle size of 700 μm or smaller 
 and are selected from the group consisting of
 (a) particles of carbon-based electronically conductive materials, 
 (b) particles of other electronically conductive materials, selected from the group of metallic electronically conductive materials which are not noble metals, and 
 (c) particles made up of a combination of carbon-based electronically conductive materials and other electronically conductive materials selected from the group of metallic electronically conductive materials, which are not noble metals; 
 
 and the total concentration of the particles (ii) is in the range 0.09 vol % to 67.8 vol %, preferably in the range 0.18 vol % to 67.8 vol %, more preferably in the range 1.9 vol % to 55.2 vol %, particularly preferably in the range 3.0 vol % to 44.2 vol %, with reference to the sum of the volumes of the enamel matrix (i) and the particles (ii), wherein the total concentration of particles (a) of carbon-based electronically conductive materials is 48 vol % or less with reference to the sum of the volumes of the enamel matrix (i) and the particles (a), 
 
 (3) application of the mixture to the surface or a portion of the surface of the base body, 
 (4) firing of the mixture applied at a temperature in the range 600° C. to 900° C. on the surface or portion of the surface of the base body, to which the mixture has been applied in step (3), so that on the surface or portion of the surface of the base body, to which the mixture has been applied in step (3), a coating comprising (i) an enamel matrix and (ii) particles, embedded in the enamel matrix, of one or more electronically conductive materials is formed, 
 (5) optional repetition of steps (2) to (4), wherein upon repetition of step (3) the mixture is applied to the area of the surface of the base body on which in a previous step (4) a coating has already been formed.