Protection of Sea Constructions against Corrosion and Biofouling
Development of Nanocomposite Coatings for Protection of Sea Constructions against Corrosion and Biofouling
Tech Area / Field
- BIO-SFS/Biosafety and BioSecurity/Biotechnology
- CHE-SYN/Basic and Synthetic Chemistry/Chemistry
- ENV-WPC/Water Pollution and Control/Environment
- MAN-MAT/Engineering Materials/Manufacturing Technology
- PHY-SSP/Solid State Physics/Physics
- SAT-SUF/Surface Transportation/Space, Aircraft and Surface Transportation
3 Approved without Funding
MISIS (Steel and Alloys), Russia, Moscow
- Maritime State University named after adm. G.I. Nevelskoi, Russia, Primorsky reg., Vladivostok\nVNIIEF, Russia, N. Novgorod reg., Sarov\nNPO Lutch, Russia, Moscow reg., Podolsk
- University of Sevillia / Departamento de Construcciones Arquitectonicas I, Spain, Seville
Project summaryTopicality of the problem. Biofouling (sometimes called “periphyton”; the word originates from the Greek peri, around and phyton, plant) is the settlement of aqueous organisms on underwater surfaces of sea-port constructions, marine oil platforms etc., fabricated from various materials: concrete, metal etc. Biofouling accelerates corrosion processes (leading to the premature failure of equipment, which is often very expensive), increases the resistance to motion for movable constructions, reduces the carrying capacity for water-intake facilities, decreases the thermal conductivity for cooling devices, etc. For this reason, prevention of biofouling started to be used well back at the very beginning of the development of marine technologies. The problem, however, is far from being solved completely, because a simultaneous combination of anti-fouling and anti-corrosion properties is required for protective coatings in natural waters.
The aim of the project is to develop compositions and methods of applying protective coatings, which are easily applicable to the fabricated component, have a high adhesion to the support (material of the construction), have a high corrosion resistance in sea water and simultaneously decrease or totally stop biofouling.
The study will be conducted in several directions:
1. Development of coatings for nonmetal surfaces. For this purpose, composite materials will be developed with the copper and nickel matrix and various reinforcing particles, such as cuprous oxide (copper(I) oxide), which serves as a toxin; nanodiamonds; alumina; silicon oxide; silicon carbide; tungsten carbide etc., as well as their various combinations.
The known anti-fouling property of various forms of copper will be used. The Project will establish which combination is more efficient: a composite with the copper matrix with reinforcing particles of cuprous oxide, or a composite with the nickel matrix and reinforcing particles of cuprous oxide with various volumetric contents. The efficiency in this case is to be understood as the ability to withstand both biofouling and corrosion in a seawater medium.
2. Development of coatings based on metal–matrix composites for metal surfaces (excluding aluminum and aluminum alloys). This is a very complicated problem. To date, the best varnish-and-paint coatings with toxins serve from one to three years. It is desirable that anti-fouling coatings serve longer. For this, it is necessary to provide for as high as possible a concentration of toxin per unit of volume of the coating; herewith, the coating should be sufficiently strong. It is for this reason that metal–matrix composites are proposed to be used; they can potentially provide for a much longer service life. Significant difficulties for the use of metal-based metal–composite coatings are presented by the possible occurrence of galvanic corrosion. In the case of emergence of a galvanic pair, the rate of corrosion would not only fail to decrease but could significantly increase. To prevent the emergence of galvanic corrosion, the following condition should be satisfied: the electrode potential of the coating material should not differ from the electrode potential of the base. To solve this problem, the studies will be carried out in two directions:
- material of the base will serve as the matrix of the metal–matrix composite for the coating, and ceramic reinforcing particles shall not change the electrode potential of the composite;
- the second direction is much more complicated, as fundamental studies are required to be carried out.
It is known that in an electrolyte (for instance, in sea water), under conditions when both metals are in contact with the electrolyte, macrocomposite material (for instance, nickel–iron laminated material) is corroded much faster that each material separately. On the other hand, it is known that alloys (mixtures of various elements at the atomic level) have their own electrode potential, and their corrosion properties are not determined by the difference of the electrode potentials of the components. Hence, the problem for fundamental studies is what the electrode potential of the nanocomposite, that is, the composite with nanosize reinforcing particles and nanosize distance between these particles commensurable with (or smaller than) the electron free path length, will be. There are no data of such regularities in the literature. So these studies are rather topical. The results of the studies will make it possible to choose the composition of the composite for coatings of metal constructions of sea-water facilities on the scientific basis.
The metal–matrix composites for use as coatings will be produced according to the following protocol: mechanical alloying of the components for producing composite granules followed by compaction of granules into bulk material.
Mechanical alloying will be performed in planetary mills with the milling bodies in the form of balls or with the quasicylindrical milling bodies. Treatment in the mills will be carried out in an inert medium (argon).
It should be noted that one of the problems of mechanical alloying is sticking of processed material to the process tool (the walls of the drums and the surface of the milling bodies), as well as increased clumping of processed material. The project will develop a method of decreasing the sticking and clumping. The granules of composite material obtained after mechanical alloying will be compacted on a press at temperatures 400–650°C and held under a load for up to 30 min.
For application of coatings, the Project will refine the method of friction cladding, which potentially makes it possible to apply coatings both on metal and nonmetal surfaces. This may solve the problem of galvanic corrosion.
Friction cladding (FC) is performed as follows. Material of the coating should be initially presented as a rod or a similar item. The main process tool is a rotated cylindrical metal brush. The brush is rotated at a high speed and is pressed against the treated surface. At another place, the rod with the coating material is pressed against the brush. By the ends of its wires, the brush scratches particles of metal fractions of a micron in size from the rod and transfers them to the treated surface. The high speed of rotation of the brush leads to a significant strength of impact of the particle on the surface; the particle welds (sticks) to the treated surface. The large number of wires in the brush and a high speed of rotation provide for a high performance and uniformity of transfer of material from the rod to the treated surface. The Project will simulate the process of applying the coatings to a surface close to a plane. Subsequently, for work with real objects it will be necessary to develop certain designs for arranging the friction cladding units at the treated surfaces.
In the Project, the thickness of the coating will be varied within the limits of 10–200 µm. Herewith, variants of applying multilayer coatings with various compositions of the layers will be investigated. The first applied layer will contain significant concentrations of cuprous oxide. In the second layer, its amount will be much lower. The lowest concentration of cuprous oxide will be in the surface layers. Herewith, we will check the possibility of including some amount of wood rosin into the surface layers, that is, will examine the assumption of the possibility of creating a monitored process with respect to the rate of leaching toxins from the upper layer of a multilayered coating to increase the service life of antifouling coatings.
The coatings developed will be subjected to a comprehensive study. The structure and properties of the coatings will be investigated. The structure of the coatings will be studied by methods of scanning microscopy, scanning electron microscopy and transmission electron microscopy, as well as by X-ray methods. The hardness and microhardness of the coatings will be determined, adhesion of the coatings to the base will be assessed. Special attention will be given to tests in situ to assess the corrosion resistance and the ability to prevent biofouling of various constructions with applied nanocomposite coatings by marine organisms under real conditions of the action of natural sea water.
It should be noted that intermediate material, that is granules of composite containing large proportions of cuprous oxide (both with the copper and nickel matrix), is also of great interest as a component for silicone and similar coatings intensively developed lately to be used under high-temperature conditions.
During implementation of the project, following tasks will be solved:
- Preparation of materials and equipment. Development of investigation methods
- Development of method of mechanical alloying for producing granules of composite materials with matrix from copper (copper alloys), nickel and with different reinforcing particles
- Development of methods of compaction of developed by mechanical alloying granules of composite materials
- Development of methods of deposition of coatings from metal matrix composites on non-metallic surface including concrete
- Development of method of deposition of coatings from metal matrix composites on metal surface similar to flat
- Investigation of structure and properties of developed coatings
- Investigation of corrosion resistance and biofouling of non-metallic constructions with developed coatings
- Investigation of corrosion resistance of developed coatings and their ability for prevention biofouling on metallic parts of sea constructions
- Comparative analysis of developed results and development of rational compositions of coatings
- Fabrication of pilot lot of specimens with developed coatings and realization of tests
For implementation of the project, high-qualification specialists will be involved; i.e. the project will be carried out on the high scientific and practical levels.
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