RU2545301C1 - Method of gas thermal spraying of polymer coating on metal products and structures - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: under method of gas thermal spraying at the first stage the metal surface is machined and degreased. Then prior to coating application the protected surface and low pressure polyethylene are pre-treated by the composition. Composition is 30% water solution of silicasol with addition of 2-4% of 3% dispersion of carbon nanotubes.

EFFECT: increased adhesion and operation properties of gas-thermal sprayed polymer coatings produced by pre-treatment of the metal surface by nanosize compositions.

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Description

The invention relates to thermal spraying of polymer coatings on metal elements and structures.

Known methods of gas-flame deposition of polymeric materials on metal and ceramic surfaces, consisting of applying a low-pressure polyethylene powder by air spraying, gas-flame heating and subsequent fixing (sticking) on the protected surface. The main processes in these cases are: preliminary mechanical or chemical preparation of the metal surface, supply of the polymer powder by air spraying, heating the polymer powder with a fire torch of a burning gas (propane or acetylene), fixing the heated particles of the polymer powder on the surface to be protected and creating a dense protective anticorrosive layer ( Borisov Yu.S., Kharlamov Yu.A., Sidorenko S.L., Ardatovskaya E.N. Gas-thermal coatings from powder materials. - Kiev: Naukova Dumka, 1987. - P. 73- 127).

However, all the described methods involve a process in stationary conditions. In addition, the resulting polymer coatings have low adhesion to the metal being protected, which does not provide long-term reliable operation under the influence of corrosive media in a wide temperature range of less than 5.0 MPa.

There is a method of creating sprayed polymer coatings with increased adhesion to 8-10 MPa on a pre-phosphated metal surface (Belarus Patent No. 8528, MKI B05D 1/08, 2006), however, this technique can only be implemented under stationary conditions, t. e. in production conditions.

Closest to the claimed method is the method according to patent No. TJ 89, register. in the state. The Register of Inventions of the Republic of Tajikistan on October 16, 2007 (Bull. No. 48), which includes pretreatment of the metal substrate with carbon nanotubes, which ensures increased adhesion and performance of polymer coatings.

The disadvantage in this case is the high cost of modifying compositions of carbon nanotubes, so the effect obtained does not meet the objectives of ensuring high operational properties of protective coatings.

The objective of the proposed technical solution is to increase the adhesion and operational properties of the thermally sprayed polymer coatings obtained by pretreating a metal surface with nanosized compositions.

To achieve this goal, before applying the sprayed polymer coatings, the metal surface is subjected to mechanical treatment and degreasing, after which a composition containing nanosized particles and a 30% aqueous silica sol with 2-4% 3% carbon solution is applied to it nanotubes. After drying for 3-5 hours, a polymer coating of powder low pressure polyethylene is applied to this surface by flame spraying. The resulting protective polymer coating is characterized by increased adhesion by 30-45%, hardness by 25-30%, heat resistance by 20-40%.

Table 1 presents data on the technical properties of thermally sprayed polymer coatings of metal structures of sewage treatment plants when treating a protected surface with nanoscale compositions.

Table 1 Operational properties of protective thermally sprayed polymer coatings of metal structures INDICATORS The method of preparing the base and processing powder HDPE No processing CNT processing Short circuit processing Short circuit + CNT processing Tensile Strength, MPa 13-17 18-35 15-24 22-28 Elongation at break,% 100-450 120-350 180-320 140-380 Melting point, ° C 110-120 125-140 125-135 130-145 Fragility temperature, ° C -70 -80 -65 -80 Water absorption in 24 hours,% 0.010 0.006 0.008 0.007 Density, kg / m ³ 920-960 930-970 925-970 970-1045 Porosity,% 1.2-1.6 0.6-0.8 0.8-1.1 0.7-0.8 Adhesion to a steel surface, MPa 5.4-6.4 8.2-9.9 8.3-9.1 9.6-12.4 Resistance in an aggressive environment, h 160-170 190-220 185-200 230-260 Estimated service life, years 7-9 10-12 8-10 14-20

As follows from table 1, when treating the protected surface with solutions of nanosized particles, the adhesion of the sprayed polymer coating increases significantly from 5.4-6.1 to 9.1-12.4, which is accompanied by a significant compaction of the film and a significant decrease in porosity from 1.2 to 0.7-0.8%. Such an improvement in quality indicators contributes to increased resistance of the protective coating in an aggressive environment from 160-170 to 230-260 hours or in terms of the estimated predicted service life and at least 14-20 years.

Nanosized particles deposited on the surface and granules of HDPE powder, acting as a catalyst and a crystallization center of the polymer coating, contribute to the ordering of the supramolecular structure and its transfer to a more enhanced pack structure, which is confirmed by an increase in all operational parameters of the polymer coating.

Table 2 shows the data on the costs and costs of the device of thermally sprayed polymer coatings of metal structures of treatment facilities during preliminary processing of the protected surface with nanoscale compositions.

table 2 Consumption of materials per 100 m ^{2 of the} protected surface Compositions for the protected surface Component Compositions Coating thickness, microns Consumption, kg / m ² HDPE powder, kg / m ² Silica sol, kg / m ² CNT, g / m ² Estimated service life, years Cost, rub / m ² Powder without treatment 350-550 0.05-0.12 0,052 - - 7-9 350-420 Short-circuit Powder 400-600 0.04-0.06 0,053 0.04 - 8-10 360-430 CNT Powder 250-300 0.03-0.07 0,065 - 0.012 10-12 400-460 Powder with processing KZ + CNT 250-350 0.03-0.05 0,060 0,03 0,054 14-20 470-580

Analyzing the above data, it should be noted that the treatment of the surface to be protected with nanoscale compositions, although it leads to a slight increase in the cost of the protective coating, however, the average cost for one year of operation of the metal structures of treatment facilities when processing the protected surface with nanoscale compositions is significantly lower. So, in case of protection without treatment, the cost of one m ² is 50-60 rubles per year, and when treated with a combination of silica and CNT, a maximum of 25-35 rubles per year, not counting the cost of the device and the maintenance of the protective coating.

Thus, the proposed method for the thermal spraying of polymer coatings on metal products and structures with preliminary processing of the protected surface with a solution of 30% silica sol with the addition of 2-4% three-percent dispersion of carbon nanotubes, leading to an increase in adhesion by 30-45%, hardness by 25- 30%, heat resistance by 20-40%, can be considered quite effective.

Claims (1)

The method of thermal spraying of polymer coatings on metal products and structures, including metal cleaning, preparation of a device, a gas burner and polymer powder, characterized in that before coating the protected surface and powder of low pressure polyethylene are pre-treated with an aqueous solution of 30% silica with the addition of 2-4% of a three percent dispersion of carbon nanotubes.