Protection against exposure to the environment is among the intricate problems of the metal age. The best scientists worldwide work to explain how corrosion damage works and how it can be prevented.
ALUMCERAMIC PROTECTS FERROUS METALS
Protection against exposure to the environment is among the intricate problems of the metal age. The best scientists worldwide work to explain how corrosion damage works and how it can be prevented.
Nevertheless, every sixth blast furnace functions to offset the corrosion losses.
Besides to causing direct economic losses, corrosion also leads to ecological and mechanical accidents polluting the environment.
As approaches to the economy were altered, these problems have become truly acute throughout the former USSR.
Corrosion resistance problem is ignored around Ukraine leading to disastrous destruction of mechanisms and structures, from farm machinery to pipelines and bridges.
The situation is nothing but critical. Therefore, all effective corrosion-resistance inventions must be greeted and supported duly.
The today’s promotion of such competitive goods requires a comprehensive approach stretching all the way from development of ecological, effective, and safe corrosion-resistant materials and relevant coating technologies, to invention of new ways to construction of corrosion-resistant structures and design of new equipment that would be able to apply protective coating outdoors.
Creation of a new composite alumceramic coating, together with the accompanying application technology and equipment, is a firm step towards solution of the corrosion problem.
To start with, structures and buildings made of iron and steel (e.g., pipelines, ship hulls, offshore drilling platforms, tanks, bridges, and the like) still suffer direct and indirect losses from corrosion even in the advanced high-tech countries, despite the major breakthrough in coating materials and coating technologies. Russia and Ukraine have virtually no factories that manufacture the international-standard rolled steel and tubes or possess high-mechanics machinery to apply efficient protective coatings.
Meanwhile, the task of enhancing quality, reliability, and useful life of iron and steel structures, as well as reducing the time and cost of construction, is nothing but burning now. There is no way to bypass this issue. Therefore, at least three related actions should be taken, namely:
create the most effective, ecological, and safe corrosion-resistant materials and commercialized application technology at the lowest cost possible;
design modern mechanical and automatic equipment and plants (factories) to manufacture coated tubes, pipes, rolled steel, and other products;
enhance the technology of building structures and installations of coated pieces.
The new composite alumceramic coating, relevant application technology, and equipment can successfully resolve all these issues.
Originally, this coating was designed to protect icebreaker hulls, offshore drilling platforms, and other structures that operate in weakly and highly corrosive environments (pH=2:12), and saline solutions. Together with anticorrosion properties, the coating had to feature high mechanical performance, e.g., wear resistance and retention of properties when subject to bending and cold punching. Besides, the new coating had to provide effective safeguard of weld seams and preserve its protective and ornamental qualities during useful life of the articles it is applied to. The coating is composite and well bound to the base article. In fact, the coating is an aluminum matrix with uniformly scattered and metallurgically bound ceramic and intermetallic particles. The coating itself is obtained by high-energy atomization of aluminum and ceramic particles melted in a supersonic plasma flux onto a pre-treated surface.
The alumceramic coating duly performs its functions only in case the application conditions are strictly adhered to. If the spraying mode is correct, all aluminum particles become completely molten and speed up to 300 to 500 meters per second, while surface of ceramic particles is fused and the particles themselves reach the speed of 200 to 400 m per second (depending on the density of the substance). Fractional composition of aluminum and ceramic powders, and the conditions of their introduction into the plasma flux are selected to ensure the lowest possible aerodynamic fragmentation of particles and enhance the number of collisions and coagulation of the flying aluminum and ceramic particles. This fosters better fusion of different materials and produces chemical bonds and intermetallic compounds. Compared to aluminum, the ceramic particles have higher thermal energy content and form the sections of microfusion with intermetallic compounds present in the coating. Regions of enhanced cohesion and density take shape around the ceramic particles. This leads to emergence of a well-bound and dense aluminum coating (0.5% porosity) featuring uniformly distributed ceramic and intermetallic particles. The coating enjoys high anticorrosion and mechanic properties. Presence of hard ceramic particles in a soft aluminum matrix greatly improves mechanical strength and wear-resistance of the coating. If one fails to meet the application requirements, he will get a mechanical mix of heterogeneous substances with coarse structure, low cohesion, and irregularly scattered and unevenly sized pours. Precisely this is the major breakthrough from renowned metallized aluminum coatings to the composite alumceramic ones.
Owing to its composite structure, the alumceramic coating produces numerous micro-galvanic cells when exposed to corrosive environment. These micro-galvanic cells stimulate chemical reactions leading to appearance of insoluble sediments. The latter seal up the pours and smooth the roughness, thus keeping the corrosive agents away from the metal. Therefore, the coating is protective and passivating.
Special plasma equipment TOPAS-80 and TOPAS-180 is applied to spray alumceramic coatings on tubes in manufacturing premises, while TOPAS-5 outfit is made use of to treat tube joints outdoors.
Bench tests of alumceramic coatings deposited on hot-water-conveyance tubes have revealed that the coating retains its original qualities and provides corrosion resistance during the whole useful life of tubes and pipes, i.e. 30 years and more. The coated articles can be utilized and stored at any temperature without additional cathodic protection.
The alumceramic coating is presently applied in Russia to protect tubes and pipes (mainly, the hot-water ones) against corrosion. Hot-water pipes are the crucial element of any central heating system. Therefore, conveyance of hot water draws large investments equaling to the cost of construction of new heat power plants and large boiler facilities. Since heat insulation accounts for about 20% of the total cost of pipelines, it is extremely important to enhance reliability and corrosion resistance. Russia currently makes use of about 30,000 km of hot-water mains made of pipes, 600 to 1,400 mm in diameter. The other hot-water-conveying pipes of smaller diameter stretch over some more 190,000 km. Most heat networks were built back in the 1950s-70s, when ineffective anticorrosion materials were applied, e.g., reinforced foam concrete, bitumen, and poor-performance mineral wool. Hence, various accidents are more than frequent. Recurrent replacement of damaged and worn-out hot-water pipes requires constant excavations and ripping up of the road surfaces, thus causing tremendous harm, especially in the large cities. Besides, about 100,000 tonnes of steel tubes and pipes are wasted annually this way.
Kapotnya-based Mosteploenergoremont of Russia has commenced production of alumceramic-coated tubes and joints for the needs of Moscow city making 50 km of tubes and pipes per year. Many years of testing have shown that the new commercialized industrial application of high-quality, enhanced-mechanical-property anticorrosion coatings on the outer tube surface is highly productive (covering about 50 square meters of the surface per hour), easily automated, makes good use of the substance sprayed (85%), and efficiently uses raw materials at low specific power consumption (1 kWh per square meter of the coating). The process can be adjusted to spray high-performance protective coats on the inside of tubes and pipes, shapes, structures, and tube joints located outdoors.
Besides, there is no need to impregnate the coating regardless the exploitation conditions for hot-water pipes. It is possible to lay coated tubes and pipes in a channel-free mode.
The experience accumulated to date was used to develop technical specification Tu 1394-002-18550-818-99, and technical requirements for alumceramic coating of tubes and joints, 57 to 820 mm in diameter.
Properties of the coating are as follows:
thickness of 0.25 to 0.3 mm;
adhesion to steel of 30 MPa;
shock strength of 50 kilogram-force per centimeter;
0.5% porosity.
The favorable results encouraged further expansion of the coating’s application in Russia and construction of public joint-stock company AKOR in the city of Ulyanovsk. AKOR’s specialty is production of anticorrosion, heat, and waterproof insulation for tubes and shapes applied in building of heat and water pipes, gas mains, petroleum pipelines, industrial pipelines, and lead lines.
The largest shareholders of AKOR include United Electric Power Complex corp. (Yediny electroenergetichesky komplex); the Committee for Trust Management of Ulyanovsk City’s Property; UlyanovskEnergo; SaratovEnergo; SamaraEnergo; and the municipal utility service of Ulyanovsk.
Manufacturing facilities of AKOR were built upon a target program of the United Power Systems of Russia (Yediniye energeticheskiye sistemy) using money coming from almost 20 regional energy companies. Since the construction works were timely and fully financed, it became possible to phase in the facilities and commence the manufacturing process on schedule.
The main facilities stretching over 11,700 square meters comprise the following items:
production line for glass-enamel coating of 57-325-mm-diameter tubes via powder spraying in an electrostatic field with subsequent induction roasting;
production line for double-layer extruded-polyethylene coating of tubes, 57 to 219 mm in diameter;
production line for heat insulation and waterproofing of tubes using the annular tube method.
The equipment installed in these production lines can make combined anticorrosive coatings, in particular:
lining glass enamel and outer alumceramic;
lining alumceramic and outer polyethylene.
At the moment, AKOR is the only Russian company that researches and tests new advanced technologies in close cooperation with various Russian and Ukrainian scientific institutions. The technologies embrace application of local ecological feedstock to manufacture frit, coatings, and heat insulation.
Application of alumceramic-lined tubes may avert abrasive wear and tear, accumulation of wax, polymers, and other sediments, consequently ensuring superb quality and pureness of the product pipelined. Besides, it becomes possible to boost the pipelining capacity, use lower-diameter tubes, slash up to 20% of power consumption during the pipelining, avoid product losses because of pipeline overhaul and repairs, lower the pollution, and decrease the chances of environmental accidents.
These facilities are the grounds to test new technologies of making anticorrosion and heat protection for pipelines.
Applying both anticorrosion alumceramic and heat-insulation polyurethane foam coatings to hot-water tubes and pipes, one may:
save 7 to 15% of heat and electric power consumption during the conveyance process;
enhance reliability of central heating for households and factories;
generate 5 to 10% more electric power in a combined mode after integrating energy and technological co-generation processes at thermal power plants;
lower the length of pipelines, the number of annual replacement of tubes, and earthwork outlays by 50 to 70%;
reduce consumption of steel tubes and pipes by 40 to 60%;
ease the environmental implications via reduced release of combustion materials, lower heat pollution of the environment, prevention of thawing and erosion of sizeable areas, lower ecological harm done by accidents involving hot water.
COMMENT
Vitaly GNATUSH, expert, DerzhZovnishInform
Russia has given a due bit of appreciation to the new anticorrosive coating invented in Ukraine investing money in higher safety of its main pipelines.
What about Ukraine? Is it possible that the country having huge tube-making facilities and problems with tube sales could fail to arrange production of the new-generation alumceramic-coated steel tubes for domestic use and for exports?
Besides, the Ukrainian authorities should take care of the anticorrosion safety of the country. There is no way to do this avoiding centralization. It is necessary to check and test the condition of hundreds of bridges, thousands of kilometers of pipelines, and thousands of tonnes of metal structures and facilities. This will allow preventing breakdowns and accidents, thus saving human lives.
Corrosion is an enemy, like radiation. Hence, we should start by setting up a Corrosion Protection Service of Ukraine.
the Metal