Preparation method for composite coating of outer surface of nodular cast iron pipe

Abstract

The invention discloses a preparation method for a composite coating of an outer surface of a nodular cast iron pipe, belonging to the technical field of corrosion inhibition of a metal material. The preparation method comprises the following steps of: (1) pretreating the outer surface of the nodular cast iron pipe; (2) the spray coating of a ceramic coating: uniformly mixing a ceramic coating raw material, and spraying the ceramic coating raw material on the outer surface of the nodular cast iron pipe by adopting flame spraying equipment, wherein the weight of the ceramic coating on the outer surface of the nodular cast iron pipe is 80-300g / m<2>, the diameter of the powder of the mixing ceramic coating raw material is 5-60 microns; the mixing ceramic coating raw material comprises Al2O3, TiO2 and Cr2O3; and (3) coating a hole sealing finishing coat. As the ceramic coating prepared by the invention has low porosity, the ceramic coating has better corrosion resistance performance; the ceramic coating has stronger binding capacity with a substrate and good wear resistance performance, can be suitable for severe environments and is low in manufacturing cost; and the hole sealing finishing coat can further increase the corrosion resistance performance of the ceramic coating.

Description

technical field [0001] The invention belongs to the technical field of metal material corrosion inhibition. Background technique [0002] At present, zinc coating is the most widely used thermal spray coating for metal pipelines. Although zinc coating has good dynamic electrochemical protection performance, zinc coating has the following disadvantages: [0003] First, the high porosity of the Zn coating weakens its anti-corrosion performance; [0004] Second, in the normal atmospheric environment, the corrosion products of Zn coating are mainly composed of zinc oxide, basic zinc hydroxide and basic carbonate which are difficult to dissolve in water. Such corrosion products have a certain self-sealing ability to block moisture However, in an environment with a high content of chloride ions, due to the intrusion of chloride ions, corrosion products such as carbonates that are difficult to dissolve in water on the surface of the Zn coating are quickly replaced by loose and eas...

AI Technical Summary

Problems solved by technology

[0004] Second, in the normal atmospheric environment, the corrosion products of Zn coating are mainly composed of zinc oxide, basic zinc hydroxide and basic carbonate which are difficult to dissolve in water. Such corrosion products have a certain self-sealing ability to block moisture However, in an environment with a high content of chloride ions, due to the intrusion of chloride ions, corrosion products such as carbonates that are difficult to dissolve in water on the surface of the Zn coating are quickly replaced by loose and easily soluble chloride compounds. At the same time, the corrosion products will also cause blistering of the coating, reduce the adhesion of the coating, cause the coating to be prone to pitting corrosion, uneven corrosion and shorten its anti-corrosion life

[0005] Third, the bonding force between the Zn coating and the metal substrate is poor, and it is prone to damage and peeling after rolling on the production line track;

[0006] Fourth, the hardness of the Zn coating is low, and its hardness is about HRC 20. It is easy to deform, slip and wear when it is impacted, impacted and rubbed by various external forces, which greatly reduces its protective ability.

[0007] Although Zn coating has the above disadvantages, in general application environments, zinc coating meets the requirements of use and becomes the preferred coating, but in some environments with harsh conditions, zinc coating cannot meet its use requirements