JP2010222664A - Surface treatment method of cast iron pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface treatment method of cast iron pipe capable of preventing the deterioration of water-tightness or the deterioration of corrosion resistance, in regard to the surface treatment method of cast iron pipe in which a thermally-sprayed film is formed on the outer surface of the cast iron pipe. <P>SOLUTION: The thermally-sprayed film having a sacrificial anode effect is formed on the outer surface of the cast iron pipe, a liquid substance having a viscosity of 20 s or less with Iwata cup is applied to the thermally-sprayed film and, further thereon, an aqueous type or a solvent type coating material is applied. According to the method, the thermally-sprayed film is formed, thereafter, the liquid substance having a low viscosity of 20 s or less with Iwata cup is supplied, therefore, at least a part of the liquid substance permeates the thermally-sprayed film, and at least a part of the liquid substance penetrates void or cleavage of the thermally sprayed film and is filled to improve water-tightness and corrosion resistance of the thermally sprayed film. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a surface treatment method for a cast iron pipe.

  As shown in FIG. 4 (a), FIG. 5 and FIG. 6 (a), in general, the cast iron pipe 1 buried in the ground is formed with an anticorrosion film 2 on the outer surface in order to prevent corrosion due to soil groundwater or the like. . As this anti-corrosion coating 2, it is known that a spray coating is formed by spraying the surface of the substrate as a sacrificial anode with a metal having a lower potential than the base metal, such as zinc or a zinc aluminum alloy, in addition to the coating film ( For example, Patent Document 1). The thermal spray coating 2 is used as an anticorrosion coating for buried cast iron pipes and the like that are required to be durable because it has excellent mechanical durability to withstand impacts and friction such as backfilled sand. Note that the cast iron pipe 1 on which the thermal spray coating 2 is formed has a coating film formed on the outer surface by subsequently coating the coating 4 as shown in FIG. 4B for the purpose of adjusting the appearance and the like. There are many cases. In FIG. 5, 6 is an insertion port, 7 is a receiving port, 8 is a rubber ring, 9 is a lock ring for preventing separation, and 10 is a centering rubber.

Japanese Patent Laid-Open No. 11-230482

  However, as shown in FIG. 7, the sprayed coating 2 has many voids and cracks in the sprayed state. Therefore, in the state where there are many voids and cracks in this way, tap water W or the like in the pipe is outside at a location corresponding to the contact portion of the rubber ring 6 in the joint as shown in FIG. 5 and FIG. In some cases, the water tightness deteriorates and the anticorrosion performance deteriorates. In particular, as shown in FIG. 6B, when the coating film 3 has a scratch K, tap water W or the like in the pipe is in direct contact with the thermal spray coating 2 and water pressure acts directly. The ratio of passing through increases and watertightness and anticorrosion performance decrease significantly.

  The present invention solves the above-mentioned problems, and provides a surface treatment method for a cast iron pipe that can prevent a decrease in watertightness and a decrease in anticorrosion performance in a surface treatment method for a cast iron pipe in which a sprayed coating is formed on the outer surface of the cast iron pipe. It is intended to do.

  In order to solve the above-mentioned problems, the present invention forms a thermal spray coating having a sacrificial anode effect on the outer surface of a cast iron pipe, and a liquid material having a viscosity of 20 seconds or less is applied to the thermal spray coating with an Iwata cup, Further, a water-based or solvent-based paint is applied thereon.

  According to this method, after the sprayed coating is formed, by supplying a liquid material having a low viscosity of 20 seconds or less with an Iwata cup, at least a part of the liquid material penetrates the sprayed coating, and the liquid material At least a part of the material enters and fills voids and cracks in the sprayed coating, thereby improving the water-tightness and anticorrosion performance of the sprayed coating.

  The thermal spray coating is preferably Zn, Al, Mg or an alloy / mixture containing them, the liquid material is preferably organic, organic-inorganic composite or inorganic, and the paint is acrylic. It is preferable to be a system or an epoxy system.

  Furthermore, in a state where the cast iron pipe is heated to a temperature of 30 ° C. or higher and 100 ° C. or lower, a liquid material is applied to the sprayed coating on the outer surface of the cast iron pipe, and the top coat is applied within 30 seconds after the application. By doing so, it is possible to shorten the drying time after the liquid material application step, and to improve the production efficiency, for example, the liquid material can be applied and the paint can be applied at the same coating site in the production line. In this case, the liquid substance is preferably a colloidal silica type or an alkyl silicate type, and good water tightness and anticorrosion performance can be obtained.

  According to the present invention, after the sprayed coating is formed, by supplying a liquid material having a low viscosity of not more than 20 seconds with an Iwata cup, at least a part of the liquid material penetrates the sprayed coating, and the liquid material At least a part of the film enters and fills voids or cracks in the sprayed coating, thereby improving the water-tightness and anticorrosion performance of the sprayed coating and improving the reliability.

(A)-(d) is sectional drawing corresponding to each process of the surface treatment method of the cast iron pipe which concerns on embodiment of this invention. It is a figure which shows simply the test apparatus used for the evaluation method of the test piece which concerns on embodiment and comparative example of this invention. It is a graph which shows the evaluation result of the test piece which concerns on embodiment and comparative example of this invention. (A), (b) is sectional drawing corresponding to each process of the surface treatment method of the conventional cast iron pipe, respectively. It is sectional drawing of a cast iron pipe joined part. (A), (b) is an principal part expanded sectional view for demonstrating the subject of the conventional cast iron pipe, respectively. It is sectional drawing (sectional photograph) which expands and shows the state in which the sprayed coating was formed in the cast iron pipe.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1A to 1D are cross-sectional views corresponding to respective steps of the cast iron pipe surface treatment method according to the embodiment of the present invention.
As schematically shown in FIGS. 1A and 1B, in the surface treatment method for a cast iron pipe according to the embodiment of the present invention, a thermal spray coating 2 having a sacrificial anode effect is formed on the outer surface of the cast iron pipe 1. Then, the spray coating 2 is supplied by applying a coating material having good permeability or a liquid material 3 that does not form a coating film with a viscosity of 20 seconds or less in an Iwata cup (see FIG. 1C). Further, a water-based or solvent-based paint 4 is further applied thereon (see FIG. 1D) to produce a cast iron pipe. 1C and 1D show the case where the coating 3a of the liquid material 3 is formed on the surface of the sprayed coating 2 after the liquid material 3 is applied. However, the present invention is not limited to this. There is no problem even if the coating film 3a is not formed.

  Here, the thermal spray coating 2 having a sacrificial anode effect is preferably Zn, Al, Mg, or an alloy / mixture containing them. The liquid substance 3 is organic, organic-inorganic composite, or inorganic. The paint 4 is preferably acrylic or epoxy.

  Cast iron pipe products are often manufactured along the production line. However, when the drying of the liquid material 3 is slow, the production line is lengthened, the liquid material 3 supplying step, the paint top-coating step, During this period, drying time must be ensured, and production line space and drying time are required. When the liquid material 3 having a low viscosity is supplied as described above at normal temperature, the permeability is often good, so that drying generally takes time. For this reason, in the production line, it is preferable to warm the cast iron pipe 1 that is the object to be coated in advance, whereby it becomes possible to speed up drying and increase productivity. Thus, by shortening the drying time after the supply (application) step of the liquid substance 3 (for example, within 30 seconds), the supply (application) of the liquid substance 3 and the coating material 4 can be performed at the same coating station in the production line. The top coat could be done. Moreover, when using what has the property of quick drying as the liquid substance 3, although there exists a tendency for the degree which the liquid substance 3 osmose | permeates the thermal spray coating 2, there is a tendency for the liquid substance 3 to increase heat resistance, It is possible to minimize the degree of penetration of the liquid material 3 into the thermal spray coating 2.

  Here, the following tests were performed in order to confirm the water tightness and anticorrosion performance of the cast iron pipe by the surface treatment method. That is, as schematically shown in FIG. 2, the sprayed coating 2, the liquid material 3, and the paint 4 formed on the entire outer periphery of a part of the cast iron pipe 1 are removed by cutting or the like. A state in which a part of the pipe 1 is exposed and the both ends of the joint ring 12 are sealed with a sealing material 11 so as to cover the exposed part of the cast iron pipe 1 and the vicinity of the exposed part from the outside. With exterior. Then, water is injected while water pressure is applied between the joint ring 12 and the outer periphery of the cast iron pipe 1. Thereby, water is penetrated from the end face of the thermal spray coating 2 or the liquid substance 3 in a state where pressure is applied, and it is confirmed whether or not water leaks to the outside. In FIG. 2, reference numeral 13 denotes a push ring that presses the sealing material 11 to ensure the sealing function of the sealing material 11, and 14 is screwed into the flange portion of the joint ring 12. A bolt for pressing, 15 a pump for sending water, 16 a pressure gauge, and 17 an on-off valve.

A cast iron pipe 1 having a diameter of 100 mm and a length of 150 mm is used as a test piece of the cast iron pipe 1 for forming the spray coating 2. Thermal spraying was performed at a spraying amount of 260 g / m ² by the method.

Then, a plurality of types of liquid substances 3 are applied to the outer periphery of the thermal spray coating 2 so that the target film thickness of the liquid substances 3 is 10 μm. Six test pieces were prepared. Thereafter, as a water tightness test, a water pressure of 15 kgf / cm ² was applied for 24 hours, and the degree of water leakage was confirmed visually. Moreover, the salt spray test was done as a corrosion-proof test. In addition, as a salt spray test, salt water was sprayed on the surface of the test piece in a state where a 50 × 50 mm cross-cut was formed in a state where the paint 4 was not overcoated, and the period until the occurrence of red rust was measured.

  The measurement results are shown in the chart shown in FIG. In the chart shown in FIG. 3, the liquid material A with prototype numbers 1 and 4 is acrylic silicon (an example of an organic-inorganic composite system), and the liquid material B with prototype number 2 is urethane (organic). Prototype No. 3 liquid substance C is an epoxy type (organic example), and Prototype No. 5 liquid substance D is a colloidal silica type (inorganic example), alkyl silicate type. (An example of an organic-inorganic composite system). The trial production number 6 is a comparative example in which the coating 4 is overcoated on the thermal spray coating 2 to which the liquid substance 3 is not supplied at all. For the anticorrosion performance, the cast iron pipe 1 of the trial production number 6 is used as a reference (1). Yes.

  As shown in FIG. 3, in the case where the liquid material C of the trial number 3 having a viscosity of 25 seconds exceeding 20 seconds in the Iwata cup is used, the trial number 6 as a comparative example in which the liquid material 3 is not supplied at all. Compared with the case of the cast iron pipe 1, the water tightness was hardly changed (not so good) and the anticorrosion performance was improved only slightly.

  On the other hand, liquid substances 4 (A, B, D) of trial numbers 1, 2, 4, and 5 having a viscosity of 20 seconds or less in the Iwata cup (all in this test example is 20 seconds) were used. In this case, the anticorrosion performance was greatly improved as compared with the case of the cast iron pipe 1 of the trial production number 6.

  Moreover, when the temperature of the cast iron pipe 1 at the time of application is 30 ° C., the cast iron pipe 1 of the trial number 1 made of the liquid material A was extremely good in both watertightness and anticorrosion performance, but made of the same liquid material A. Even in the cast iron pipe 1 of the trial production number 1, when the temperature of the cast iron pipe 1 at the time of application is 100 ° C., both the water tightness and the anticorrosion performance are compared with the production of the cast iron pipe 1 of the trial production number 1. Slightly decreased. On the other hand, when the liquid substance D with improved heat resistance was used, good water tightness and anticorrosion performance were obtained.

  As can be seen from these results, at least a part of the liquid material 3 is applied to the thermal spray coating 2 by supplying a low viscosity liquid material 3 of 20 seconds or less after the thermal spray coating 2 is formed. It penetrates and at least a part of the liquid material 3 enters and fills voids and cracks in the thermal spray coating 2, improving the water tightness and anticorrosion performance of the thermal spray coating 2 and improving the reliability.

1 Cast iron pipe 2 Thermal spray coating 3 Liquid substance 4 Paint

Claims (6)

  A sprayed coating with a sacrificial anode effect is formed on the outer surface of the cast iron pipe, and a liquid material having a viscosity of 20 seconds or less is applied to this sprayed coating with an Iwata cup, and a water-based or solvent-based paint is further applied thereon. A surface treatment method for a cast iron pipe, characterized by being painted.   2. The surface treatment method for a cast iron pipe according to claim 1, wherein the thermal spray coating is Zn, Al, Mg or an alloy / mixture containing them.   The surface treatment method for a cast iron pipe according to claim 1 or 2, wherein the liquid substance is organic, organic-inorganic composite, or inorganic.   The surface treatment method for a cast iron pipe according to any one of claims 1 to 3, wherein the paint is acrylic or epoxy.   Apply the liquid material to the sprayed coating sprayed on the outer surface of the cast iron pipe with the cast iron pipe heated to a temperature of 30 ° C or higher and 100 ° C or lower, and apply the top coat within 30 seconds after application. The surface treatment method for a cast iron pipe according to any one of claims 1 to 4.   The surface treatment method for a cast iron pipe according to claim 5, wherein the liquid substance is a colloidal silica type or an alkyl silicate type.