Ductile iron pipe with composite coating

Abstract

The application discloses a nodular cast iron pipe with a composite coating and belongs to the technical field of metal corrosion prevention, comprising a nodular cast iron pipe base body, a composite outer coating coated on the outer surface of the nodular cast iron pipe base body and an inner coating closely attached to the inner surface of the nodular cast iron pipe base body, characterized in that the composite outer coating comprises an alkali-activated gel layer and a zinc-based coating, the zinc-based coating is arranged between the outer surface of the nodular cast iron pipe base body and the alkali-activated gel layer, the alkali-activated gel layer is an alkali-activated slag fly ash corrosion-resistant gel material, and the zinc-based coating is one or more of a pure zinc coating, a zinc-aluminum alloy coating or a zinc-rich coating layer. The alkali-activated gel layer provided by the application is coated on the inner or outer surface of the pipe and provides further corrosion protection for the nodular cast iron pipe, so that the pipe can be used in extremely harsh construction environments, and has extremely strong weather resistance in acidic soil and overhead fields.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal corrosion protection, and in particular to a ductile cast iron pipe with a composite coating. BACKGROUND

[0002] Ductile cast iron pipes and fittings have been applied in direct-buried and overhead environments for more than a hundred years, and are widely used in the fields of water conservancy, water supply, and drainage. In the overhead field, the coating is required to have very high weather resistance, not only to resist rain washing, but also to prevent powdering failure caused by long-term sunlight irradiation. In the trenchless construction field, the coating not only needs to withstand the corrosion of soil, but also needs to meet the corrosion failure caused by coating damage during trenchless construction.

[0003] In recent years, in order to meet the wear resistance of pipeline coating in the trenchless drag construction method, a fiber cement mortar coating has appeared as a pipeline external corrosion protection coating. Cement is an indispensable building material in construction engineering and is the largest artificial material used by humans. However, cement still has some deficiencies, such as poor permeability resistance and acid resistance, and surface coating protection of cement is an effective measure to improve its performance. Traditional organic composite coating materials have poor high-temperature resistance, short service life, and poor adhesion, and their practicability is increasingly limited. For example, patent (CN105384417B) discloses a coating raw material composition, a ductile cast iron pipe, and a preparation method thereof, but the product has the following problems related to the mortar composition and the production method.

[0004] (1) The slag silicate fiber cement layer has strong wear resistance, but when the product is applied in acidic soil, water needs to be added to increase lubricity for trenchless drag engineering. Acidic soil easily forms an acidic solution that penetrates into the fiber cement coating under the action of water, resulting in increased corrosion porosity and further causing pipeline corrosion.

[0005] (2) When the slag silicate fiber cement layer ductile cast iron pipe is applied in the overhead field, it is subjected to long-term rain washing and sunlight irradiation. Water penetrates into the cement concrete under the action of rain, and the water is lost under the action of sunlight, which easily causes the cement layer to powder and crack day after day, and long-term application will cause the pipeline to be locally corroded.

[0006] In summary, there is currently no corresponding long-term applicable corrosion protection coating in overhead and harsh buried environmental conditions, and the existing corrosion protection coating cannot guarantee long-term application of the pipeline. SUMMARY

[0007] The technical problem to be solved by the present application is to provide a ductile cast iron pipe with a composite coating, which is coated with an alkali-activated gel layer on the inner or outer surface of the pipe to provide further corrosion protection for the ductile cast iron pipe, can be used in extremely harsh construction environments, and has strong weather resistance in acidic soil and overhead fields; and the alkali-activated gel layer coated on the inner wall of the pipe can be used to transport water with strong corrosiveness, such as seawater, domestic or industrial sewage, etc.

[0008] To solve the above technical problems, the technical solution adopted by the present application is:

[0009] The ductile cast iron pipe with a composite coating comprises a ductile cast iron pipe base body, a composite outer coating coated on the outer surface of the ductile cast iron pipe base body, and an inner coating closely attached to the inner surface of the ductile cast iron pipe base body, the composite outer coating comprises an alkali-activated gel layer and a zinc-based coating, the zinc-based coating is arranged between the outer surface of the ductile cast iron pipe base body and the alkali-activated gel layer; the alkali-activated gel layer is an alkali slag fly ash corrosion-resistant gel material; the zinc-based coating is one or more of a pure zinc coating, a zinc-aluminum alloy coating, or a zinc-rich coating.

[0010] The further improvement of the technical solution of the present application is that the thickness of the alkali-activated gel layer is 2-15 mm.

[0011] The further improvement of the technical solution of the present application is that the thickness of the alkali-activated gel layer is 3-10 mm.

[0012] The further improvement of the technical solution of the present application is that the alkali-activated gel layer further comprises uniformly mixed fibers, the fibers are one or more of polypropylene fibers, basalt fibers, and glass fibers; and a specific proportion of fibers is added to the raw materials before the alkali-activated gel layer is coated.

[0013] The further improvement of the technical solution of the present application is that in the alkali-activated gel layer, the fibers account for 0.5-2% of the alkali-activated gel material, and the alkali-activated gel layer further comprises slag, river sand, water, sodium silicate, sodium hydroxide, and cellulose.

[0014] The further improvement of the technical solution of the present application is that a permeable waterproof layer is further arranged on the outer surface of the alkali-activated gel layer, and the permeable waterproof layer is an organic silicon waterproof agent.

[0015] The further improvement of the technical solution of the present application is that a bonding layer is further arranged between the alkali-activated gel layer and the zinc-based coating, and the bonding layer is an epoxy resin coating.

[0016] The ductile cast iron pipe body is internally provided with a corresponding anticorrosion coating according to the use.

[0017] The ductile cast iron pipe body is internally provided with a corresponding anticorrosion coating according to the use.

[0018] The anticorrosion coating is an alkali-activated gel layer or an alkali-activated gel layer with fibers.

[0019] Thanks to the above technical scheme, the present application has the following technical progress:

[0020] The ductile cast iron pipe with a composite coating improves the strength and toughness of the coating, and the anticorrosion life and anticorrosion effect of the anticorrosion coating. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is an axial sectional view of the ductile cast iron pipe with a composite coating in the present application;

[0022] Among them, 1 is a ductile cast iron pipe body, 2 is an epoxy coating layer, 3 is an alkali-activated gel material layer, 4 is an anticorrosion lining, and 5 is a penetrating waterproof layer. DETAILED DESCRIPTION

[0023] The present application will be further described in detail below in combination with the drawings and examples:

[0024] As shown in the drawings, Figure 1 A ductile cast iron pipe with a composite coating comprises a ductile cast iron pipe body 1, a composite outer coating coated on the outer surface of the ductile cast iron pipe body 1, and an inner coating closely attached to the inner surface of the ductile cast iron pipe body 1. The composite outer coating comprises an alkali-activated gel layer 3 and a zinc-based coating layer 2, and the zinc-based coating layer 2 is arranged between the outer surface of the ductile cast iron pipe body 1 and the alkali-activated gel layer 3.

[0025] The alkali-activated gel layer 3 is an alkali slag fly ash corrosion-resistant gel material, and its thickness is 2-15 mm, more preferably 3-10 mm. The alkali slag fly ash corrosion-resistant gel material has strong acid, alkali and salt resistance, and meets the requirements of GB / T29423 standard.

[0026] The alkali-activated gel layer 3 also includes uniformly mixed fibers, which are one or more of polypropylene fiber, basalt fiber, and glass fiber. When the alkali-activated gel layer is applied, a certain proportion of fibers is added to the raw materials to improve the toughness of the entire coating. In the alkali-activated gel layer, the fibers account for 0.5-2% of the alkali-activated gel material, and the alkali-activated gel layer also includes slag, river sand, water, sodium silicate, sodium hydroxide, and cellulose.

[0027] The outer surface of the alkali-activated gel layer 3 is also provided with a permeable waterproof layer 5, which is an organic silicone waterproof agent. The addition of the waterproof agent not only forms a water-blocking layer through permeation and crystallization, but also penetrates into the pore channels of the alkali-activated gel layer using osmotic water pressure. Through complex crystallization reactions between the active materials in the waterproof agent and the moisture and free active ingredients in the alkali-activated gel layer, insoluble crystal complexes that block internal capillary channels and micro-cracks are formed, thereby improving the density, durability, and impermeability of the alkali-activated gel layer. In addition, the waterproof agent can chemically react with alkali metals in the alkali-activated gel layer to form insoluble crystals. These crystal structures can seal and fill micro-cracks, pores, and pores. When there is no water in the gel layer, it is in a dormant state. Once it comes into contact with water, it will activate and form new crystals again, filling and sealing new leakage defects, providing permanent self-repairing function for the mortar layer. At the same time, the addition of the waterproof agent can improve the freeze-thaw resistance and acid corrosion resistance of the coating material.

[0028] The zinc-based coating 2 is one or more of a pure zinc coating, a zinc-aluminum alloy coating, or a zinc-rich coating. The zinc-based coating 2 meets the requirements of GB / T 17456.1 and GB / T 17456.2.

[0029] The alkali-activated gel layer 3 and the zinc-based coating 2 also include an adhesive layer, which is an epoxy resin coating layer. By coating an epoxy resin coating layer on the surface of the zinc-based coating 2, further corrosion protection is provided, and adhesion between the alkali-activated gel layer is achieved, preventing the coating from peeling off.

[0030] The inner surface of the ductile cast iron pipe base 1 is provided with an inner lining layer 4, which is an alkali-activated gel layer, a cement mortar layer, an epoxy resin lining layer, a polyurethane lining layer, a polyethylene lining layer, an epoxy powder lining layer, or a cement mortar lining layer with a sealing layer.

[0031] Corrosion-resistant coatings can be provided inside the ductile cast iron pipe base 1 according to the purpose, and the alkali-activated gel layer and the alkali-activated gel layer with added fibers can also be used as an inner wall corrosion-resistant coating.

[0032] In summary, the alkali-activated gel layer provided by the application is coated on the inner or outer surface of the pipeline, further provides corrosion protection for the ductile cast iron pipe, can enable the pipe to be constructed in extremely harsh construction environment, and has extremely strong weather resistance in acidic soil and overhead fields.

Claims

1. A ductile iron pipe with a composite coating, comprising a ductile iron pipe substrate (1), a composite outer coating applied to the outer surface of the ductile iron pipe substrate (1), and an inner coating closely adhering to the inner surface of the ductile iron pipe substrate (1), characterized in that: The composite outer coating includes an alkali-activated gel layer (3) and a zinc-based coating (2). The zinc-based coating (2) is disposed between the outer surface of the ductile iron pipe substrate (1) and the alkali-activated gel layer (3). The alkali-activated gel layer (3) is an alkali slag fly ash corrosion-resistant gel material. The zinc-based coating (2) is one or more of a pure zinc coating, a zinc-aluminum alloy coating, or a zinc-rich coating. The thickness of the alkali-activated gel layer (3) is 3-10 mm; The alkali-activated gel layer (3) also includes uniformly mixed fibers, which are one or more of polypropylene fibers, basalt fibers, and glass fibers; a specific proportion of fibers are added to the raw materials before the alkali-activated gel layer is coated. In the alkali-activated gel layer, fibers account for 0.5-2% of the alkali-activated gel material, and the alkali-activated gel layer also includes slag, river sand, water, sodium silicate, sodium hydroxide, and cellulose; An adhesive layer is also included between the alkali-activated gel layer (3) and the zinc-based coating (2), and the adhesive layer is an epoxy resin coating layer; The inner surface of the ductile iron pipe substrate (1) is provided with an inner lining layer (4), which is an alkali-activated gel layer, a cement mortar layer, an epoxy resin inner lining layer, a polyurethane inner lining layer, a polyethylene inner lining layer, an epoxy powder inner lining layer, or a cement mortar inner lining layer with a sealing layer. Appropriate anti-corrosion coatings are provided inside the ductile iron pipe substrate (1) according to the application; The anti-corrosion coating is an alkali-activated gel layer or an alkali-activated gel layer with added fibers.

2. The ductile iron pipe with composite coating according to claim 1, characterized in that: The outer surface of the alkali-activated gel layer (3) is further provided with a penetrating waterproof layer (5), which is an organosilicon waterproofing agent.

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