Corrosion-resistant coating "contact" and method of deposition thereof on metal surfaces

FIELD: chemistry.

SUBSTANCE: corrosion-resistant coating can be used for time-interval corrosion prevention (conservation) of contact surfaces of frictional bolted assemblies within large-sized bridge steel-works transported and stored after manufactured at factory of origin. Corrosion-resistant coating is made of composition containing chlorvinyl enamel CV-114, slightly soluble corrosion inhibitor Acor-1 and rheological additive that is modified carbamide solution in N-methylpyrrolidone, deposited on metal surface been layered, vapour blasted and hardened.

EFFECT: elimination repeated vapour blasting of contact surfaces of joint steel-works prior to be field mounted, and maintaining of friction properties of vapour blasted metal surfaces joint with high-strength hardware.

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The invention relates to the protection of metals from corrosion and can be used for temporary corrosion protection (conservation) of the contact surfaces of the friction connection of large bridge structures during their transportation and storage after manufacture at the factory.

Corrosion is a natural phenomenon, defined as fracture of solids caused by chemical or electrochemical processes on their surface when interacting with the environment. The word corrosion comes from the Latin corrosio - erosion. If corrosion is a process, the corrosion products (rust) is one of its results. Corrosion can lead to dangerous and costly damage to various structures, from bridges and public buildings structures and chemical products manufacturing industry. A special place is occupied by man-made disaster, caused by destruction of the supporting structures of buildings and constructions. About 20% of the total amount of metal is lost every year due to corrosion, and huge amounts of money spent on protection against corrosion.

When choosing a method of corrosion control takes into account not only the characteristics of the metal itself, but also its operating conditions. Special difficulties selecting a method of protecting metal operated in environments with complex p is the parameters (temperature, concentration, pressure), changing in the process, which often occurs in chemical processes. All used to practice the methods of corrosion protection can be divided according to the nature of their impact on the metal and on the environment.

Methods of corrosion protection are endless depending on the types of corrosion, and it has a direct effect on the development of schemes of corrosion protection. Corrosion control is carried out using methods developed on the basis of well-known scientific principles, but it remains one of the most serious and complex problems of modern technology.

Ukrupnennom modern methods of protection against corrosion can be divided into two areas:

1) increase the chemical resistance of structural materials, insulation metal surface from the corrosive environment different coatings,

2) decrease the aggressiveness of the production environment or reduce corrosion by applying an external current (cathodic protection).

In the first direction protection methods are typically implemented prior to the beginning of the production operation. In the second direction methods of protection may only be made during operation and are not associated with any pre-treatment of metals prior to their use.

Coatings used to protect metals from corrosion, divide n is metal, non-metallic and formed by chemical or electrochemical treatment of a metal surface.

It should be noted that the effectiveness of the corrosion protection is greatly facilitated by proper surface preparation, which consists in degreasing and removing scale, rust and foreign substances (if any) from the steel surface prior to application on the factory primer or primer.

The best way steel surfaces may be cleaned by abrasive-jet method with the use of abrasive materials, such as metal shot, superslick, corundum, garnet, silica sand, glass beads, aluminum shot, crushed fruit pits, dry ice. In our case, in relation to large-sized structures, abrasive-jet machining is needed to ensure the highest settings fractionate contact surfaces, sochlenennykh by compression of high-strength fasteners. The peculiarity of the contact surfaces is the need for temporary corrosion protection for the period from metal fabrication at the factory before erection work at construction sites.

Steel surfaces may be cleaned from rust in the following ways :

Mechanical cleansing poverhnosti by means of metal brushes, chisels, etc.

Abrasive-blasting - blasting with compressed air with the use of abrasive materials, such as metal shot, superslick, corundum, garnet, silica sand, glass beads, aluminum shot, crushed fruit pits, steel sand, dry ice.

Waterjet cleaning is conducted using a suspension of abrasive in water jet under high pressure. One of the most important positive factors - the lack of dust, but the use of water involves the following thorough drying to prevent rust.

Dynamic gas cleaning is used for cleaning of metal of a thickness exceeding 6 mm is Used the principle of additional acceleration of the abrasive particles in the jet stream of gas burned fossil fuels.

Chemical cleaning - etching acids and alkalis. There are a full wipe (to clean metal and processing modifiers rust, which is mainly used on steel surfaces in hard to reach for other types of processing.

Each of these methods has its own advantages and disadvantages, but they all relate to ecological and sanitary-hygienic (for staff) consequences, one must also consider economic factors.

After cleaning for corrosion protection otnositel the small products are applied passivation, phosphating, electroplating. For large structures are used in paints, enamels and special structures.

There are a large number of different compounds, compositions, enamels, lacquers, etc. issued by various domestic and foreign manufacturers and applicable including for temporary corrosion protection.

Known composition, representing conservation lubricant based on mineral oils with the addition of jet fuel (T-1, polyvinyl-n-butyl ether (thickening additive of venepal) and oxidized petrapetra (additive Tits-3), to increase the corrosion resistance of the injected mixture of essential oils of Agerola with Cetelem in a specific ratio of components (RF Patent No. 2029779). However, this preservative lubricating material does not retain the required frictional characteristics of the surface after its removal, as even a small amount of reduces the coefficient of friction during the compression of the contact surfaces of high strength hardware.

Known RF Patent № 2019550. The inventive coating based on alkyd, acrylic, epoxy and vinyl resin is injected as a corrosion inhibitor phenolic derivative mercaptobenzthiazole certain patterns in the amount of 0.5 to 5.0% based on the weight of solid substances is and paint material. An example of a phenolic derivative is the product of the condensation of 2-mercaptobenzthiazole with a carbonyl compound and a phenol (2,6-disubstituted phenol, 2 -, or 2,4-disubstituted phenol). This coating protects the metal from corrosion for up to one year, but to remove it you need to use sandblasting or chemical cleaning methods, affecting working conditions of personnel and causing additional work during construction operations.

Currently, the most popular compositions, allowing for removal of the coating with the lowest complexity.

Known removable floor "VpCl-388" manufacturing Sweden, distributor firm "International", s-Petersburg. It is formed of the high viscosity of the original composition. Coating color blue. Material technology when applied (few stains), the hiding power of the coating is good, but due to the high viscosity of the formed coating visible brush marks. The drying time of the single-layer coating sufficiently large to 1.5 hours. The coating is elastic, but is removed from octobertuesday metal surface with difficulty torn when removing the individual pieces. On the surface of the metal under the coating, because it is prepared with water-based, see numerous points of corrosion of metal.

Removable floor "DL-22-0000" produced by German company LANKWIZER LACKFABRIK is formed from low viscosity, fluid fundamentals. Coating color dark blue, material technology when applied (no streaks), the hiding power of the coating is good. The drying time of the single-layer coating of 0.5 hours. The coating is sufficiently elastic, easily removed with octobertuesday metal surface without leaving visible traces of coverage. Points of corrosion under the coating is not detected. After exposure for 14 days Shimamoto cover "DL-22-0000 remained excellent. Corrosion of the metal under the coating also not detected. Lack of coverage is its adaptability to manufacture, since the desired thickness of coating (100-120 μm)to enable its easy removal, can be formed only for 4 layers. In addition, the formation temperature coatings: from +10 to +30°that makes it difficult to protect the contact surfaces of the bridge structure in winter.

Known and domestic removable coating, such as enamel HT-7101 CENTURIES of production of the Zagorsk LKZ and floor "Carbonates" (Saint-Petersburg, VNIIK them. Lebedev). The disadvantage of the first of them is the high film thickness 250 μm, and more), which requires a large amount of material, in addition, during the removal of the coating can break. The disadvantages of the second cover should include the fact that at the stage of curing, the appearance of pitting corrosion of metal under the coating is C-moisture, contained in waterborne latex. After removal of the coating is observed color change of the metal.

The above removable cover in varying degrees, do not satisfy the objectives to protect the contact surfaces of large structures.

The closest to the claimed composition (chemical composition and functional purpose) is easily removable coating (option B3-7 GOST 9.014-78), which is a mixture of red-brown paint enamel XB-114 (92 wt.%) and additives mineral oil AKOR-1 (8 wt.%). The basis of odnoupakovochnye enamel XB-114 is perchlorovinyl resin. Oil-soluble corrosion inhibitor AKOR-1 is made of nitrated base oils M11 M8 or by adding the alkalization 9-11 wt.% technical stearin. The disadvantage of the prototype is the possibility of formation of a coating of the desired thickness (100-120 μm) only 3-4 layers to ease its removal. This circumstance complicates the use of coatings on the prototype on the ceiling and vertical planes of metal, substantially increases the complexity of the work and the consumption of the starting material. It should also be noted that according to paragraph 8 of Annex 5 GOST 9.014-78 floor of the prototype is not allowed to put on the metal surface after blasting and sand truinas processing, because the resulting coating is difficult to remove with a rough surface, leaving a non-removable particle cover. However, the requirement abrasive-jet machining of the contact surfaces with a roughness not less than R_z=40 μm is mandatory for the contact surfaces of the bridge structure, as when the compression strength of hardware you want to save the frictional performance of connected surfaces to ensure the strength of the connections and exceptions "razbaltyvaniya" connections.

An object of the invention is the creation of easily removable anti-corrosion composition free from the above disadvantages and provides temporary corrosion protection frictional connection of large bridge structures.

The technical result is achieved due to the fact that in the known composition comprising vinyl chloride based (enamel XB-114) and soluble corrosion inhibitor (AKOR-1), is added rheological additive (BIK-410) in the amount of 0.5-1.0 wt.%. Changed also the quantitative content of the known components: paints and vinyl chloride enamel in the range from 95 to 97 wt.%, and soluble corrosion inhibitor (AKOR-1) is in the range from 2.5 to 4.5 wt.%.

Rheological additive is a solution of modified urine is ins N organic. After adding it to the coating in an amount of from 0.5 to 1.0 wt.% the three-dimensional structure of the composition is built in such a way that prevents the formation of nodules and simultaneously saguday and increases the thixotropy (narastanie) get paint material.

The choice of this rheological additive as a regulator of thixotropy was the result of numerous studies, the volume of which in the mixture of known components (vinyl chloride enamel XB-114 and corrosion inhibitor AKOR-1) were injected liquid and powder thickeners, as well as various brands of rheological additive BIC, and the weight percent of components varied in different limits.

The analysis of the received results of research work were identified and quantified ranges of each component that comprises a corrosion-resistant coating "Contact".

Depending on the actual conditions of application of anti-corrosion coatings (time of year) the specific composition of the original composition is obtained by mixing specified amounts of enamel paint and soluble corrosion inhibitor, taken in certain amounts (wt.%). After mixing the two components in the mixture injected liquid rheological additive BIK 410 as the last component of the formulation. The amount of injected additives BIK-410 can vary depending on the time of year: a lower concentration in the winter, but large concentrations (up to 1.0%) at elevated temperatures. With the introduction of rheological additive continuously stirring composition throughout its scope to avoid gelatinization. A consequence of the introduction of a rheological additive occurs within 2-4 hours after making it to the mix is that it is slow (in managed mode) of the composition, forming a very fine, needle-like microcrystals, which then form a three-dimensional (lattice) structure of the coating. Best results are achieved with the introduction rheological additive BIK-410 at 0.8% mass%, if the ambient temperature is within 18-20°C.

Floor "Contact" saves technological properties in the range of negative temperatures (not below minus 15° (C) to above freezing temperatures (up to 35°).

The operating temperature range of the coating "Contact" is from -40 to +40°, which also increases the attractiveness of its application for the temporary protection of surfaces of large structures.

Among the most characteristic examples of the need to use antikorrozionnoe cover "Contact" it should be noted following the ways of metallokontstruktsy:

- contact surfaces of the bolt factory and the circuit connection elements (walls and zone beams, the elements of lattice systems, elements, links);

pin (working) surface mounting pads (gussets);

flange welded mounting elements, for factory-prepared;

- a surface that is not painted in the manufacture of structures for protection of adjacent painted surfaces from damage by corrosion products during storage and installation (upper zone of composite steel and concrete structures and the like).

Application easily removable anti-corrosion composition "Contact" is any of the known ways: manually with a brush or roller, dipping or spraying using a pneumatic nozzle device.

General operations technology application easily removable anti-corrosion composition "Contact" same as that used when applying similar coatings, primers and the like, including surface preparation and the coating.

Known invention (Patent RF №2174161)in which to achieve quality improvement of surface cleaning encouraged to machining metal surface at the same time in the treatment zone of the proposed chemical composition. The time of contact with the surface of status is made at least 30 seconds in the treatment area and not more than 3 hours after the end of treatment at ambient temperature and treated surface from +10 to +30° C.

As a corrosion-resistant substance is proposed to use a composition containing phosphoric acid, the cleaning agent based on sodium carbonate, trisodium phosphate and sodium metasilicate, water, zinc oxide, sodium hexametaphosphate, hypophosphite calcium and the product of the interaction of alkali metal salts benzoic acid and chromic acid (product of BHI), and washing the preparation additionally contains a surfactant OP-7 or OP-10 at a certain ratio of components.

Practically this method combines the preparation of the surface with the simultaneous application of anti-corrosion phosphate layer(s).

However, in this method of protection cannot be used sandblasting, which provides GOST 9.014-78 "Temporary corrosion protection products". Phosphate composition is complex, and therefore much more expensive than proposed in the present invention composition.

In addition, application of phosphate composition containing water, excludes the possibility of its application in the range of freezing temperatures.

The closest way of preparing and applying a corrosion-resistant coating is a method, including surface preparation, application of a protective coating and curing. Moreover, the preparation of surfaces produced by abrasive blasting prior to exposure of the surface pores with is definitely the total area of the holes, and then put a protective coating layer in the form of solutions polysiloxanes, thus increasing their penetration in bare pores. Then utverjdayut coated delay it for a time from 6 to 24 h in the permissible temperature range and maintaining the values of air humidity in the range from 30 to 100% (Application No. 97116446).

The disadvantage of this method is a very long time of curing. In addition, the coating of the prototype does not take into account some of the operational requirements (Shimamoto coverage, ensuring fractionate surface after removing the cover), which should provide the claimed composition "Contact".

In this regard, in the known method, including the preparation of metal surfaces by abrasive blasting, coating application, curing the coating with a certain time delay changes, namely:

- corrosion coating is carried out in several layers (preferably in two layers), and the total layer must have a certain thickness (preferably 100-120 μm);

- exposure after the application of each coating layer for curing should not exceed 0,25-1,0 h (optimal composition - 0.25 h).

Below are examples of implementation of the invention.

Example 1

To 15.0 kg Lakokraska the Oh enamel brand HV-114 add 0,5 kg soluble corrosion inhibitor, which apply known composition AKOR-1. The components are thoroughly mixed, the mixture is kept for two hours, and then add about 125 g rheological additive BIK-410. The composition is thoroughly mixed and incubated until thick within 2-4 h of the Optimal composition for the preparation of the original paint material for the inventive corrosion-resistant coating "Contact" (in wt.%) provided its application temperature 18-20°With the following: paint enamel (XB-114) - 96,0; corrosion inhibitor (AKOR-1) - 3,2; rheological additive BIK-410 is 0.8. Then, after thorough mixing, the composition is applied in 2 layers on the metal surface prepared by abrasive-jet method to the degree of purity Sa 2.5 and roughness Rz≥40 μm. After application of the first layer with a thickness of 50-60 μm, the flow rate of one layer is 300-400 g/m²) and shutter speed for at least 0.25 hour, put the second layer of anti-corrosion composition "Contact" with the same flow rate. Subsequent exposure for one hour is required for full curing (drying) of the coating.

As a result, the metal surface of the structure formed coating thickness of 100-120 microns. The adhesion strength of the coating film of the composition "Contact" at a thickness of 100-120 μm is sufficient for the formation of protective corrosion coatings. At the same time the I floor, thanks to a specified thickness, quite durable and can be easily removed from the metal before performing installation work. After nadareski sharp tool it is easily removed "stocking", including surfaces prepared by abrasive-jet method.

Floor "Contact" saves technological properties when it is applied in the range of negative temperatures (not below minus 15° (C) to above freezing temperatures (35°C)and the operating temperature range of the coating "Contact" is from -40 to +40°C.

Other examples of implementation of the proposed composition " contact" and the resulting parameters of its application are given in the table below.

The analysis of this table allows to draw conclusions about what the range of the set values of the quantitative part of the original composition (wt.%): paint enamel - 95,0-97,0; soluble corrosion inhibitor of 2.5 - 4.5 and rheological additive is 0.5 to 1.0, and the exposure time of each layer (the cure) - 0,25-0,5 h, in the natural drying, selected correctly (examples 1, 2, 4,).

The best is the composition of example 1, somewhat worse results in example 2, in which the flow rate of the composition is increased due to the need for the application of the third layer, as in example 4, it is necessary the application of even four layers.

The worst results were obtained in example 6, where the number of layers reaches four, and the drying time of 1.5 hours

Example 8 shows the results of applying a corrosion-resistant coating on the prototype, which is the worst. The performance of all other examples of the application of a corrosion-resistant coating "Contact" to some extent better than the prototype.

Using the coating composition of "Contact" is used to completely eliminate the re-abrasive-jet machining of the contact surfaces of the joined structures before installation at the building sites and stores, unlike the prototype, the frictional properties of the prepared abrasive-jet method of metal surfaces, connected by high-strength fasteners. This is achieved inthat case, if you carry out the coating immediately after fabrication of the structural members in the factory.

In this case, significantly reduces the labor for installation, improve working conditions of personnel and environmental conditions at the construction site.

Corrosion-resistant coating "Contact" was the industrial validation on multiple bridge objects Saint Petersburg at their repair or restoration, as well as the number of objects.

The results showed the feasibility of its application in the practice of other construction companies.

1. Corrosion-resistant coating made from a composition containing vinyl chloride enamel XB-114, oil-soluble corrosion inhibitor AKOR-1 on the basis of nitrated base oils with added during the alkalization 9-11 wt.% technical stearin and rheological additive is a solution of a modified urea N-organic, in the following ratio, wt.%:

2. The production method of coating a metal surface, including jet-abrasive the th surface cleaning then applying the composition according to claim 1 in several layers, with exposure time for curing each layer within 0.25 to 1.0 hours

3. The method according to claim 2, characterized in that the composition is applied in two layers with time delay for curing each layer within 0.25 to 1.0 hours