RU2743604C1 - Method of anti-corrosion protection of cathode-polarizable underground metal structures with layer of polymer compound in insulating coating, polymer compound for an insulating coating of cathode-polarizable underground metal structures and use of anionite microparticles - Google Patents

Abstract

FIELD: construction, oil and gas industry.

SUBSTANCE: invention can be used in construction and during repairing works of underground metal structures and, preferably, for field, technological and main oil, gas, product pipelines. Method of anticorrosive protection of cathode-polarizable underground metal structures with a polymer layer of mastic compound in an insulating coating consists in cathode polarization from an external direct current source of the metal structure, whereon an insulating coating is preliminarily formed, which adheres to the metal surface on the basis of a primer. Then, the next adhesive bonding anticorrosion layer is formed in the form of a polymer compound. After that, an exterior waterproof coat is developed on it. To form an adhesive binding anticorrosion layer, a polymer compound is used that contains a polymeric thermosetting or thermoplastic binder and a sufficient amount of anionite microparticles in the appropriate ionic form. Preliminarily, the number of anionite microparticles in the appropriate ionic form is determined in the composition of the polymer compound, the ions of which, according to the laboratory test for determining the peeling area of ​​protective coatings during cathodic polarization, can reduce the peeling area relative to the original polymer binder without adding anionite by more than 75%. Once the primer has dried, a flowable polymer compound is applied to it with a layer thickness of 0.5 to 3 mm, with simultaneous application, using a thermoplastic tie layer, of a reinforcing geotextile in the form of a fiberglass mesh. Thereafter, as an exterior waterproof layer, a metal structure, for example a pipeline, is wrapped with a polymeric film material to form an adhesive-adherent insulating polymeric layer compatible with the type of the polymer adjacent to the metal surface to be protected. In case of a thermosetting binder, a fluid high-resistance polymer compound, adhesive-compatible with the polymer-anionite layer, is used to form the exterior waterproof layer. Disclosed are a polymer compound and the use of anionite microparticles in an appropriate ionic form as an additive to the polymer compound.

EFFECT: improved anticorrosive protection of polymeric thermosetting and thermoplastic polymeric coatings by increasing durability of the adhesive bond with the metal surface while leveling the risks of underfilm corrosion under the peeled coating.

5 cl, 2 dwg, 4 tbl

Description

The invention relates to the construction and repair of underground metal structures, and preferably, field, technological and main oil, gas, product pipelines in order to protect them from electrochemical corrosion in conditions of cathodic polarization and is intended to increase the durability of cathode-polarized, mainly steel structures and structures , in particular, underground gas and oil pipelines, as well as improving environmental friendliness in the production of protective coatings using polymer passive protection.

Transportation of oil, gas and oil products through pipelines is the most efficient and safest way to transport them over long distances. The durability and trouble-free operation of pipelines directly depends on the effectiveness of their anti-corrosion protection.

Traditionally, anti-corrosion protection of underground metal structures, including pipelines, is carried out using forced cathodic polarization from an external DC source, the negative pole of which is connected to the protected metal structure with an insulating coating formed on it. The protected metal structure plays the role of a cathode, and for the formation of a closed current circuit, the positive pole of the source is connected to the auxiliary electrode - the anode, which is in the same environment (soil, water) as the protected object, which is negatively polarized and its potential is shifted to the value , significantly suppressing the metal corrosion process, (see, Cherkasov N.M., Gladkikh I.F., Filimonov V.A.Experience in the use of insulating coatings based on the Asmol oil polymer for the repair of main pipelines. Oil and Gas Business, 2010, p. 1- 9).

At the same time, the inhibition of corrosion processes of metals under various coatings and the practical simplicity of their application have led to the widespread use of various coatings for anticorrosive protection. The reliability of the adhesive bond of the substrate with the coating in this case largely determines the effectiveness of their anti-corrosion protection [see. articles: Kolotovsky A.N., Kuzbozhev A.S., Aginey R.V. and others. Assessment of damage to underground pipelines on the basis of VTD data before overhaul of insulation // Environmental protection in the oil and gas complex, 2009, No. 3; Maocheng Yan, Shuang Yang, Cheng Sun, Jin Xu, Tangqing Wu, Wei Ke. Corrosion of Pipeline Steel under Occluded Coating Disbondment in a Red Soil Environment // Corrosion Science, Vol. 93, 2015, pages 27-38; Aginey P.B., Alexandrov Yu.V. Investigation of ECP criteria in flaking the insulating coating of a gas pipeline // "Territory NEFTEGAZ", No. 2, 2010, p. 23-26].

Widely used coatings are various polymer coatings that provide waterproofing of steel pipelines.

The long-term practice of operating well-known insulating thermoplastic (for example, bituminous and bitumen-polymer) and thermosetting (for example, epoxy) coatings for pipelines indicates that the physical nature of the adhesive bonds of the coating with the metal cannot ensure their preservation for a long period. When these coatings are used under conditions of cathodic polarization, a significant factor in the weakening of efficiency, leading to the above problems, is their high cathodic peeling. In this case, the electrolyte begins to penetrate under the peeling coating and anodic dissolution of the metal with the penetration of cathodic reducing oxygen into the exfoliated defect. The alkaline medium formed in this corrosive element contributes to the exfoliation of the coating due to the dissolution of the layer of amphoteric oxides, the decomposition of the polymer, and the hydrolysis of interfacial adhesive bonds, which ultimately significantly reduces the effectiveness of protection and leads to the formation of corrosion foci [see. Articles Nguyen, T., Hubbard, J.W., McFadden, G.V. Mathematical Model for the Cathodic Blistering of Organic Coatings on Steel Immersed in Electrolytes. The Journal of Coatings Technology 63: 43-52, 1991; Cherkasov H.M., Gladkikh I.F., Filimonov B.A., Experience in the use of insulating coatings based on asmol oil polymer for the repair of main pipelines. Oil and gas business, 2010, p. 1-9; G. Williams, H.N. McMurray, M.J. Loveridge. Inhibition of corrosion-driven organic coating disbondment on galvanized steel by smart release group II and Zn (II) -exchanged bentonite pigments. Electrochimica Acta 55 (2010) p. 1740-1748].

Currently, the direction of obtaining protective materials with a self-healing adhesive bond is developing.

The closest to the invention in technical essence and the achieved result is a method of anticorrosive protection of cathode-polarizable underground metal structures with a polymer layer of mastic in an insulating coating, which consists in cathodic polarization from an external direct current source of a metal structure, on which an insulating coating is preliminarily formed, which is based on the primer adheres to the metal surface, then the next adhesive binding anticorrosive layer is formed in the form of a polymer compound and then an outer waterproofing layer is formed on it (see RF patent No. 2666917, class F16L 58/12, publ. 09/13/2018).

In the aforementioned patent, bitumen-polymer mastic is used as an adhesive anticorrosive binder, a layer reinforced with glass mesh in a two-layer protective bag with a protective heat-shrinkable film applied above the pour point and providing waterproofing of steel pipelines, where the first cation layer adhered to the protected metal is made of a bitumen composition. Moreover, the cation exchanger introduced into the bitumen binder contains metal ions, which form insoluble hydroxides under conditions of cathodic polarization, as counterions of its fixed ionogenic groups.

Due to the introduction of the cation exchanger into the adhesive binder, the problem of preventing cathodic peeling of the bitumen-polymer coating, a significant increase in its service life with a simultaneous increase in the durability of the adhesive bond with the protected surface and, as a consequence, an increase in the reliability of the active cathodic anticorrosive protection of metal (steel) structures is solved.

However, the coatings made according to the known method and using the known mastic have significant disadvantages: the toxicity of the heavy metals included in the coating, the limited temperature range of the bitumen binder used, the high cost of reagents for obtaining the required ionic form of the cation exchanger.

The technical problem solved by the invention is the elimination of these disadvantages, while simultaneously preventing the cathodic peeling of polymer coatings, a significant increase in its service life and an increase in the durability of the adhesive bond with the metal surface while leveling the risks of underfilm corrosion under the peeled coating, and, as a consequence, increasing the reliability of active cathodic anti-corrosion protection of metal (steel) structures, and improving environmental friendliness with a decrease in the cost of their production.

The technical result consists in increasing the efficiency of anticorrosive protection of polymeric thermosetting and thermoplastic polymeric coatings by increasing the durability of the adhesive bond with the metal surface while leveling the risks of underfilm corrosion under the exfoliated coating with a simultaneous decrease in their ecotoxicity.

In part of the method, as an object of the invention, the technical problem posed is solved, and the technical result is achieved by the fact that the method of anticorrosion protection of cathode-polarizable underground metal structures with a polymer layer of mastic in an insulating coating consists in cathodic polarization from an external DC source of a metal structure, on which an insulating coating is formed, which on the basis of a primer adheres to the metal surface, then the next adhesive bonding anticorrosive layer is formed in the form of a polymer compound and then an outer waterproofing layer is formed on it, and for the formation of an adhesive bonding anticorrosive layer a polymer compound containing a polymeric thermosetting or thermoplastic a binder and a sufficient amount of anionite microparticles in the appropriate ionic form, and the exact amount of microparticles in the polymer compound is preliminarily determined particles of anion exchanger in the appropriate ionic form, the ions of which, according to a laboratory test for determining the peeling area of protective coatings during cathodic polarization, can reduce the peeling area relative to the initial polymer binder without the addition of an anion exchanger by more than 75%, and then, after the primer has dried, a flowable polymer compound is applied to it at a thickness its layer from 0.5 to 3 mm with simultaneous application of a reinforcing geotextile in the form of a fiberglass mesh using a thermoplastic bonding layer and then, as an outer waterproofing layer, a metal structure, for example a pipeline, is wrapped with a polymer film material with the formation of an adhesive-adjacent insulating polymer layer compatible with the type of polymer adjacent to the metal surface to be protected, and in the case of a thermosetting binder, a flowable high-resistance polymer compound, adhesive-compatible with polymer-anio, is used to form the outer waterproofing layer with a thread layer.

In terms of the substance as an object of the invention, the technical problem posed is solved, and the technical result is achieved by the fact that the polymer compound includes a mixture of BND-60/90 and BN-70/30 bitumen, a thermoplastic elastomer on a divinyl styrene base, a plasticizer and synthetic anion exchanger AB-17- 8 in silicate or phosphate or in aluminate ionic forms with fraction sizes up to 100 μm, with the following composition

components, wt. %:

bitumen BND-60/90 5-45 bitumen BN-70/30 45-85 thermoplastic elastomer 4-7 plasticizer 2-10 anion exchanger AV-17-8 4-10

The polymer compound preferably contains thermoplastic elastomer DST-30R-01 as a thermoplastic elastomer.

The polymer compound preferably contains industrial oil I-40 as a plasticizer.

As an application, as an object of the invention, the technical problem posed is solved, and the technical result is achieved by using anionite microparticles in the appropriate ionic form as an additive in a polymer compound to form an adhesive binding anticorrosive layer when performing a coating on a protected metal surface.

It is known (see article NN Petrov, AS Alovyagina, MN Mikheev, NN Bukov, VT Panyushkin. The effect of the ionic form of the introduced diatomite on the cathode peeling of bitumen-polymer coatings. Physicochemistry of the surface and protection of materials, 2020, volume 56, No. 3, pp. 323-329) that the study of the adhesive durability of materials, including under conditions of cathodic polarization, includes a test for cathodic peeling (Test for determining the peeling area of protective coatings during cathodic polarization - GOST 51164-98. Appendix B). This method well simulates the real conditions of the coating life cycle. In this case, the peeling rate depends on the nature of the system under test and its adhesive resistance, and, durability, and its correlation for polymer systems of a similar nature, testifies to these characteristics quantitatively.

In the course of the study, the influence of the strongly basic anionite AB-17-8 (Russia, GOST 20301-74) in various ionic forms, introduced as an active filler, was revealed on the adhesive resistance of polymer-anionite protective systems during their cathodic polarization. The following ionic forms of the anionite were studied: the initial chloride form, as well as nitrate, hydroxo, sulfate, chromate, carbonate, silicate, phosphate, and aluminate forms.

The strongly basic anion exchanger AB-17-8 in the initial chloride form and its modified samples in the composition of a polymer compound containing, in addition to the ion exchanger, also BND-60/90 bitumen - 5-45%, BN-70/30 bitumen - 45-85%, were investigated. thermoplastic elastomer - 4-7%, plasticizer - 2-10%), and an outer waterproofing layer - a polyethylene film (1 mm thick) as part of a two-layer bitumen-polymer coating - is applied to the layer of the polymer compound.

The main physical and chemical characteristics of bitumen-polymer mastic are presented in table. one.

During the study, the anionite was converted into the studied ionic forms: The original anionite AB-17-8 in Cl ^- form was placed (in wt%) in 5% aqueous solutions of the corresponding sodium salts (nitrate, sulfate, chromate, carbonate, silicate , orthophosphate and aluminate), as well as (in wt%) in a 5% sodium hydroxide solution at a volume ratio of anionite - solution of 1: 4 and kept at ambient temperature for 7 days. Then the obtained anion exchangers were filtered off, washed with a 5-fold excess of distilled water, and dried to constant weight at a temperature of 110 ° C in a drying oven.

Then the quantitative control of the ionic substitution process was carried out, namely, the obtained anionites were analyzed for the content of mobile anion. To do this, a weighed portion of the ion exchanger was placed in a 0.7 M sodium chloride solution and allowed to stand with gentle stirring for 5 hours, then an aliquot was taken. Then the concentration of the corresponding anion was determined according to the methods indicated in table. 2 and recalculated for the content in the anionite phase.

The quantitative measure of the substitution process (substitution) was determined by the formula:

where COE is the static exchange capacity of the anionite, mg-eq / g, Z is the charge of the mobile ion, C _An is the found content of the anion, mmol / g.

The obtained values of substitution for all samples of the anion exchanger were in the range of 97 ± 5%.

Polymer compound preparation.

Mixing of preliminarily prepared powders of the AV-17-8 anionite in the studied ionic forms (in wt%) with a mixture of bitumen ((BND-60/90 bitumen -5-45% and BN-70/30 bitumen 45-85%) , thermoplastic elastomer - 4-7% and plasticizer - 2-10%), at the flow temperature of bitumen in pre-selected conditions, ensuring uniform distribution of the filler in the polymer matrix. In this case, the filler was introduced until the maximum possible concentration (10% (wt.) Was reached, ensuring the invariability of the initial physical and mechanical characteristics of bitumen.

Before the introduction, the obtained anionite was dried at a temperature of 110 ° C to an air-dry state, and the powder obtained by grinding in a planetary mill was sieved. Subsequently, a fraction of particles passed through a 100 μm sieve was used.

The technique of coating a steel surface was investigated.

On steel plates preliminarily prepared to the Sa 3 grade (low-carbon steel St. 3, Russia), heated to a temperature of 100 ± 20 ° C, the studied melts of a polymer compound with a thickness of 1-2 mm (melt temperature 180-190 ° C) were applied with simultaneous application (without loss of bitumen fluidity) of the outer waterproofing layer in the form of a polymer tape when rolling it with a roller until it adheres to the binder. The obtained samples 100 × 100 mm were left to cool at a temperature of 25 ± 5 ° C in an open atmosphere for 3 days, and then they were tested to determine the resistance to cathodic peeling according to GOST 51164-98 (Appendix B).

In the course of the study, the dependence of the magnitude of the cathodic peeling of bitumen-polyelectrolyte systems on the introduced counterions was revealed (n = 4, P = 0.95). shown in FIG. one

The inhibition of peeling of the studied bitumen-anionite systems was investigated depending on the type of introduced ion.

To compare the effect of the nature of the active ion introduced in the anion exchanger with the physicochemical effect of its introduction, the coefficients of inhibition of peeling of the studied systems were calculated using the formula (2):

where S ₀ is the peeling area of the original polymer binder, cm ² , S _i is the peeling area of the polymer binder with the introduced anion exchanger in the corresponding ionic form, cm ² , Z _i is the peeling inhibition coefficient,%.

The obtained values of the coefficients are presented in Fig. 2.

Such tests have also been carried out for epoxy systems with the introduction of the AV-17-8 anionite in various ionic forms. At the same time, the results did not differ from those for bitumen-polymer systems within 5%.

It is known (see, for example, RF patent No. 2666917) that polymer-ion exchange systems are of practical importance, for which inhibition of exfoliation is observed above 75%. And for systems with inhibition of cathodic peeling above 85-90%, the adhesive durability, and as a consequence, the effectiveness of anti-corrosion protection, increases 3-5 times (see the article by N.N. Petrov, A.S. Alovyagina, M.N. Mikheev, NN Bukov, VT Panyushkin. The influence of the ionic form of the introduced diatomite on the cathodic peeling of bitumen-polymer coatings. Physicochemistry of the surface and protection of materials, 2020, volume 56, No. 3, pp. 323-329)

The ratio of the components was investigated when the ion exchanger was introduced into the bitumen-polymer mastic with different ratios of its components (see table 3).

Thus, it was found that the introduction of a strongly basic anionite AB 17-8 (GOST 20301-74) with counterions into the composition of the polymer compound makes it possible to obtain inhibiting peeling of anticorrosive coatings above 75% relative to the initial ones without the introduction of anionite, while an increase in the adhesion resistance of the resulting composites is observed. and the components used are not toxic.

An example of the implementation of the claimed method of anticorrosive protection of cathode-polarizable underground metal structures with a layer of polymer compound in an insulating coating of the above composition.

The technological scheme of the process of obtaining and applying the proposed bitumen-polymer mastic includes the following steps:

1. Getting the original polymer compound.

The required amount of the specified ingredients with the specified physical and mechanical properties is weighed out and the mixture is homogenized at a temperature not higher than the melting temperature (180-195 ° C).

A solid anionite filler is obtained, for which the initial strongly basic anionite AB 17-8 is placed in a 5% (wt.) Aqueous solution of the corresponding salt, with a volume ratio of anionite: solution from 1: 3 to 1: 5 and ion exchange is carried out until the pH of the aqueous medium is stabilized ... After that, the ion exchanger is washed with deionized water until neutral, then the resulting anion exchanger in salt form is dried to an air-dry state and ground to a fraction size of no more than 100 microns. The obtained powder of anionite is introduced in salt form into the initial composition (in wt%), consisting of bitumen BND-60/90 - 5-45%, bitumen BN-70/30 - 45-85%, thermoplastic elastomer - 4-7% and a plasticizer - 2-10% at the bitumen melting temperature (180-210 ° C) and homogenize the mixture.

The resulting mass is briquetted into a form convenient for transportation and use and packed in a polymer film.

2. Formation of a coating on a steel surface.

A primer is applied to the preliminarily prepared metal surface of the structure, for example, a bituminous primer, which provides the desired adhesive characteristics, which can be used as the Transcor mastic (manufactured by Delan, Russia).

After the primer has dried, the melt of the obtained polymer compound is applied at a layer thickness of 1.5-2 mm with the simultaneous application of a layer reinforcing geotextile in the form of a glass mesh and a polymer tape.

The main characterized properties of the resulting coating are presented in table. four.

and Kantemirova I.F. (Conducting an expert assessment for protective coatings of pipelines, Oil and Gas Business, 2009, - p. 1-24) after exposure in a salt fog chamber, in the methodology, the durability of the coatings was assessed using a five-point system relative to the reference coating, which was a three-layer polyethylene coating factory applied.

The resulting coating provides its purpose - to prevent contact of the corrosive medium with the protected surface due to the low water permeability of the insulating layer. At the same time, it has an increased anticorrosive efficiency with high durability under conditions of cathodic polarization due to the suppression of cathodic peeling from the surface of the protected metal. The resulting coating has good adhesion to the steel surface, the required physical and mechanical characteristics, resistance to corrosive water environment, water resistance.

Thus, as a result of the implementation of the proposed method using the proposed polymer compound, an increase in the effectiveness of anti-corrosion protection of metal structures, for example, of steel under active cathodic protection, is achieved by increasing the adhesive resistance and durability of the coating under cathodic polarization while leveling the risks of underfilm corrosion under the peeling coating. This achieves the possibility of complete prevention of cathodic peeling and a significant increase in the service life of coatings based on polymer-anionite compositions. And also the damage to the health of personnel and the environment is minimized due to the absence of toxic components in the composition of the coating, which made it possible to obtain it to protect cathode-polarizable structures, including underground and underwater gas, oil, and product pipelines, ensuring its purpose.

Claims (6)

1. A method of anticorrosive protection of cathode-polarizable underground metal structures with a polymer layer of mastic in an insulating coating, which consists in cathodic polarization from an external direct current source of a metal structure, on which an insulating coating is preliminarily formed, which on the basis of a primer adheres to the metal surface, then is formed the next adhesive bonding anticorrosive layer in the form of a polymer compound and then an outer waterproofing layer is formed on it, characterized in that to form an adhesive bonding anticorrosive layer, a polymer compound is used containing a polymer thermosetting or thermoplastic binder and a sufficient amount of anionite microparticles in the corresponding ionic form, and preliminary determine in the composition of the polymer compound the amount of anionite microparticles in the corresponding ionic form, the ions of which according to the laboratory test for determining the exfoliation area protective coatings with cathodic polarization allow to reduce the peeling area relative to the initial polymer binder without the addition of an anion exchanger by more than 75%, and then, after the primer has dried, a flowable polymer compound is applied to it with a layer thickness of 0.5 to 3 mm, with simultaneous application using a thermoplastic a bonding layer of a reinforcing geotextile in the form of a fiberglass mesh and then, as an outer waterproofing layer, a metal structure, for example a pipeline, is wrapped with a polymer film material to form an adhesive-adherent insulating polymer layer compatible with the type of polymer adjacent to the metal surface to be protected, and in the case of a thermosetting binder for the formation of the outer waterproofing layer, a flowable high-resistance polymer compound is used, adhesive-compatible with the polymer-anionite layer. 2. Polymer compound, including a mixture of bitumen BND-60/90 and BN-70/30, a thermoplastic elastomer on a divinylstyrene base and a plasticizer, characterized in that it contains a synthetic anion exchanger AB-17-8 in silicate, or phosphate, or aluminate ionic forms with fraction sizes up to 100 μm, with the following composition of components, wt. %: bitumen BND-60/90 5-45 bitumen BN-70/30 45-85 thermoplastic elastomer 4-7 plasticizer 2-10 anion exchanger AV-17-8 4-10 3. The polymer compound according to claim 2, characterized in that it contains thermoplastic elastomer DST-30R-01 as the thermoplastic elastomer. 4. Polymer compound according to claim 2, characterized in that it contains industrial oil I-40 as a plasticizer. 5. The use of microparticles of anionite in the appropriate ionic form as an additive in the polymer compound for the formation of an adhesive binding anticorrosive layer when performing a coating on a protected metal surface.

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