Anticorrosion coating composition with improved stability, and coated substrate

Abstract

The invention relates to an anticorrosion coating composition for a metal substrate, comprising at least: (a) a particulate metal, (b) chromic acid and/or one of its derivatives, (d) a pH regulator such as zinc oxide (ZnO) or cobalt carbonate (CoCO3), (e) a high-boiling solvent of the polyol or glycol ether type, (f) an organic cosolvent with a specified solubility parameter, (g) a defoaming solvent of the mineral spirit or naphtha type, (h) a system of nonionic surfactants comprising at least one water-soluble surfactant and a surfactant which is soluble in mineral spirit, and (i) water. It also relates to metal substrates covered with the anticorrosion coating resulting from heating after the application of the composition to the substrate.

I claim: 
     
       1. An anticorrosion coating composition for a metal substrate which comprises: (a) from approximately 10 to approximately 40% by weight of a particulate metal,   (b) from approximately 1 to approximately 12% by weight of boric acid and hexavalent chromiun,   (c) from approximately 0.5 to approximately 4% by weight of a pH regulator,   (d) from approximately 7 to approximately 30% by weight of a high-boiling solvent of the group consisting of polyols and glycol ethers,   (e) from at least approximately 0.1 to approximately 10% by weight of an organic cosolvent with a solubility parameter of 10.8±1,   (f) from approximately 0.1 to approximately 10% by weight of mineral spirits   (g) from approximately 1 to approximately 3% by weight of a system of nonionic surfactants comprising at least one water-soluble surfactant which has a HLB close to but higher than 10 and a surfactant which is soluble in mineral spirits which has a HLB close to but lower than 10,   (h) water.   
     
     
       2. The composition as claimed in claim 1, wherein the particulate metal is chosen from of the group consisting of zinc, aluminum, cadmium and mixtures and alloys thereof which have a negative normal electrode potential whose absolute value is greater than that of iron. 
     
     
       3. The composition as claimed in claim 1, which comprises from approximately 0.5 to approximately 6% by weight of mineral spirits. 
     
     
       4. The composition as claimed in claim 1, which comprises a quantity of .Iadd.said .Iaddend.organic cosolvent with a specified solubility parameter, which is at least practically equal to the quantity of mineral spirits, on a weight basis. 
     
     
       5. The composition as claimed in claim 4, wherein the organic cosolvent has a solubility parameter lying between the solubility parameters of .[.said.]. mineral spirits and of the high-boiling solvent. 
     
     
       6. The composition as claimed in claim 4, wherein the organic cosolvent is chosen from the group consisting of ethylglycol acetate and propylene glycol methyl ether acetate. 
     
     
       7. The composition as claimed in claim 1, which additionally comprises a thickening agent. 
     
     
       8. The composition as claimed in claim 1, which additionally comprises up to approximately 10% of solid lubricant. 
     
     
       9. The composition as claimed in claim 8 wherein the solid lubricant is selected from the group consisting of PTFE and MoS 2 . 
     
     
       10. The composition as claimed in claim 1, wherein the particulate metal is introduced into the composition in the form of a paste comprising the said metal in the form of particles and mineral spirit. 
     
     
       11. The composition as claimed in claim 10, wherein the paste comprises from approximately 85 to approximately 92% by weight of particulate metal and from approximately 8 to approximately 15% by weight of mineral .[.spirit.]..Iadd.spirits.Iaddend.. 
     
     
       12. The composition as claimed in claim 1, when made by a process wherein the metal is introduced into the composition in the form of dry particles. 
     
     
       13. The composition as claimed in claim 1 in which said pH regulator is selected from the group consisting of zinc oxide and cobalt carbonate. 
     
     
       14. The composition as claimed in claim 4 in which said cosolvent has a solubility parameter between about 9 and about 12. 
     
     
       15. The composition of claim 1 in which said cosolvent is selected from the group consisting of ethylglycol acetate and propylene glycol methyl ether acetate. 
     
     
       16. The composition of claim 1 in which said thickening agent comprises hydroxyethyl cellulose. 
     
     
       17. The composition according to claim .[.1.]. .Iadd.7 .Iaddend.wherein the hexavalent chromiun is introduced by the addition of chromic acid.