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MAIN / ABOUT US / Articles / Water-dispersion paints for protection of reinforced concrete and steel structures against corrosion
Water-dispersion paints for protection of reinforced concrete and steel structures against corrosion |
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V. P. Lobkovsky, Ph. D., chief technology OOO SPE “TEPLOHIM "
Magazine "ISOT" 6/27/03 The problem of reliable and durable protection of structures and buildings made of reinforced concrete and metal (carbon steel, cast iron, aluminum) against corrosion, and concrete, plaster, brick and other surfaces from the weather remains very important to the present. In this case, the problem of maintaining or giving aesthetic form to buildings and facilities also remains actual.
One of the most widely used methods of solving these problems is to create the protective lacquer coating on the surface of decorative materials.
It is obvious that for such coatings of most interest are paints of environmentally sound technologies: water-dispersion. Their advantages are undeniable: the complete absence of toxic with a pungent odor and flammable solvents, fire and explosion in the process of application, low temperature curing, non-waste technology of production, relatively low cost with high quality characteristics of the formed coatings.
Coating materials from UHRA series refer to such materials. A distinctive feature of these paints is the presence of specific active anti-corrosive acidic components that provide:
- Firstly, high adhesion of coatings due to chemical interaction with the surface of concrete / reinforced concrete;
- secondly, the transformation of iron oxides, which form the rust on the steel surface in a layer of iron phosphates tightly bonded to the unoxidized metal, and inhibition of corrosion processes.
Paint "UHRA-1505" (VD-AK-1505) is designed for corrosion protection of reinforced concrete, and also for protection from adverse weather of surfaces of concrete / concrete, brick, cinder block, wood, tile materials (particleboard, DSP, fiberboard, plywood) , hardboard and asbestos material (slate). Recommended for painting of facades and interiors for industrial, civil and housing purposes.
The use of acrylic dispersions as film-forming provides high resistance of coatings obtained by UV radiation and other adverse weather conditions. The color scheme has a wide range of applied mineral and organic pigments and is determined by the requirements of consumers.
For closing defects in the preparatory works is recommended to use a primer "UHRA-00504. Primer "UHRA-0501" provides a consolidation of loose crumbling foundations, leveling of their absorbability essentially (20%) reduces the paint consumption.
For internal works is proposed paint "UHRA-2509" (VD-AK-2509).
Paint "UHRA-1503" (VD-AK-1503) is designed to protect against corrosion of the metal (carbon steel, cast iron, aluminum), as a primer, and for finishing. For metal structures, operating in very aggressive environments is recommended to use a combination of coating: as a primer - paint "UHRA-1503" (VD-AK-1503) with overlapping by chemically resistant enamels of types XC, XB. Recommended for protective and decorative painting of the metal for various purposes (engineering products, pipelines, building structures, bridges, sea and river ships, railway and metro carriages, bus bodies, submersible pumps, industrial fans, etc.). It is allowed by Sanitary and Epidemiological Surveillance authorities for corrosion protection of internal surfaces of pipes and tanks of drinking water. Red-brown, brown, black and green colors are produced.
These paints form scratch-resistant coatings at temperatures from - 60o to 100o C at slightly aggressive environment (on SNIP - 02/03/1911 -85), without the limits of humidity.
According to its characteristics coatings formed by paints "UHRA" are not inferior to traditional coatings, such as oil, pentaphthalic, acrylic, glyptal and others, and often surpass them:
- impact-resistance - not less than 50 cm, GOST 6806;
- elasticity in bending - 1 mm, GOST 6806;
- resistance to the static action of water - not less than 48 hours, GOST 9,403;
- resistance to mineral oils - no less than 24 hours, GOST 9,403;
- washability - no more than 0.5 g/m2, GOST 28196;
- light resistance - not less than 4 hours, GOST 21903;
- abrasion resistance - not less than 20 kg (sand), GOST 8747;
- adhesion to concrete, to the metal - 3.51 points (MPa), GOST 28574, GOST 15140;
- life expectancy based on accelerated testing in a climate chamber - more than 10 years.
Complex tests performed in NIIZhB showed the high performance of coatings formed by paints "UHRA-1505" on the surface of structural concrete.
The protective properties of coatings on concrete were assessed by factors of diffusion permeability, water resistance, cold resistance, water absorption.
Damage to concrete structures in aggressive environments is connected usually with the corrosion of reinforcement due to inadequate thickness and density of the protective layer of concrete (cement stone of concrete). The reaction of concrete with acidic gases such as carbon dioxide of atmosphere (carbonation), is the most typical of impacts, which influences nearly all concrete structures. The intensity of the carbonation of concrete is determined by the diffusion permeability of the surface of the neutralized concrete layer.
Cracks that occur during the operation of structures also accelerate the process of destruction of cement and, therefore, the processes of corrosion of reinforced concrete.
Comprehensive tests performed by the laboratory of corrosion and durability of concrete and reinforced concrete structures NIIZhB showed that the use of Coatings UHRA-1505 for the protective coating increases the frost resistance and frost salt resistance of concrete and reinforced concrete, significantly reduces the absorption of water, several times increases the duration of the protective action of the concrete layer for armature, that makes the paint to be particularly effective when used as weather-coating.
For the protection of concrete structures that allow the disclosure of cracks during operation (beams, roofs, ledgers, etc.), the formulation of paint "UHRA-1505" is developed, it is based on acrylic copolymers as foaming agent, the distinctive feature of which is the higher resistance to UV radiation and high elasticity (crack-resistance) of coatings.
Indicators of fracture and adhesion are crucial criteria for evaluating of coatings used for corrosion protection of reinforced concrete structures, in which is possible the formation and opening of cracks up to 0,3 mm (SNIP - 03.02.2001 -84 *), in operation under the influence of thermal and mechanical effects.
The obtained data agree well with the existing practice of applying paint UHRA-1505 and observations in a number of years of the state of coating on concrete, as well as on plaster and brick.
Paint "UHRA-1505" (VD-AK-1505) is being successfully used for painting of the facades of buildings and structures for various purposes in many Russian cities (concrete and reinforced concrete, plaster, brick and other surfaces). It established itself as well for protective and decorative painting of slate.
To obtain the optimum thickness of coatings on concrete 140-160 mm, the paint consumption is 350-380 g/m2.
Along with the protection of reinforced concrete to date there remains an urgent problem of corrosion protection of structures and buildings made of carbon steel and cast iron. It is known that the rust on the steel surface has a loose structure, is weakly bonded to the unoxidized metal, and freely flows to the surface of the water vapor, oxygen and corrosive gases contained in the industrial atmosphere. In addition, iron oxides are the catalytic converters to further the process of corrosion.
Paint "UHRA-1503" forms on the metal surface a dense coating, significantly impeding the penetration of corrosive gases on its surface.
As it was shown by tests conducted by CNIIS, according to its protective characteristics (water-resistant coating, corrosion resistance under high humidity and temperature, and the additional impact of 3% aqueous solution of sodium chloride) they are 1,5-2 times higher than the primer "Unicor-2" (VD-KCH-0251) and paint WD-KCH-124 (WD-KCH-0586).
Paint "UHRA-1503" has been successfully applied as protective coloration of railway cars, buses, industrial fans, submersible pumps, and welded structures for various purposes, including construction, water mains and valves, etc. The optimal thickness of the coating on the metal surface formed by deposition of two coats of paint "UHRA-1503" is no less than 90 microns at a flow rate of paint 150-180 g/m2.
For practical application is very important to use a good paint compatibility "UHRA-1503" with other coatings, both as a ground, and as a capping layer for finishing. Traces of corrosion on the steel surface do not reduce the quality of the coating. |
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