| A covering system possessing wear resistance and corrosion resistance on steel structure surface is usually made up of different coatings with relevant functions, such as anti-corrosion primer, intermediate coating and functional finish, etc. On the basis of a great deal of document data, theory analyses and experimental work, the dissertation studied on a set of matching coating system catering to different requirements of coatings'properties, such as physical and mechanical properties, tolerance of chemical mediator, corrosion prevention, anti-aging, anti-mildew, wear resistance, drag reduction and anti-cavitations. Evaluation and assessment of the performances of the matching coating show that some research results have been achieved.Based on the theory for adhesion strength failure of wet film the extremely complicated thermodynamic process of organic coatings'bonding failure was typified and optimized in the dissertation. The antirust mechanism of phosphate is discussed in detail. Based on the above theoretic work a new kind of anti-corrosive primer was developed to replace those traditional primers consisting of heavy metals, such as lead, chromium and cadmium. This kind of primer consists of epoxy resin with high performances, non-benzene solvent, auxiliary materials, new type curing agents and inert fillers, such as zinc phosphate, aluminum tripolyphosphate, zinc oxide as well as composite antirust pigment, iron oxide red and mica powder. It is nontoxic and characterized by fast drying speed, good mechanical property, excellent salted water resistance, high resistance against boiling water and long life when tested by salt spray test, etc.Anti-wear intermediate coatings were prepared with a developed solvent-free anti-wear paint. The paint was concocted by using low molecular weight epoxy resin toughened with butadiene acrylonitrile rubber as main film-former, surface modified flake pigments as additives, reactive diluents and anti-settling agents as viscosity-and-homogeneous degree modifier, curing agent as well as other auxiliary materials. A solvent-free paint product with the best comprehensive properties was screened through testing coatings'performances, such as anti-permeability, resistance against salt spray, resistance against heat and humidity, tolerance of chemical mediator, anti-aging and wear resistance. Results show that wear resistance and corrosion resistance of the developed solvent-free coating are 20%?50% higher than that of epoxy or polyurethane top finishes. A kind of fluorocarbon resin with the best outdoor weather ability and the longest life when tested by QUV are selected by comparing and analyzing with other different fluorocarbon resin producers. It was used as main film-former and together with weather-resistant fillers, self-made antifungal agents, dispersants, anti-settling agents, anti-foaming agents, flatting agents, smooth agents and curing agents for preparing a new kind of air-drying fluorocarbon coating. Performance tests were carried out to evaluate weather ability, anti-fungal ability, resistance against salt spray and tolerance of chemical mediator of the coating. Results show that its fungus-resistant degree is zero, i.e. no moulds growth, life is 5000h when tested by QUV, gloss retention is above 90% and other properties has not changed obviously after 48-month outdoor exposure.Hydrophobic and hydrophilic additives were respectively developed to solve the regular problems of poor dirt resistance for traditional air-drying fluorocarbon coatings, especially for matt or semi-matt ones. The two kind of additives developed can both increase the cleaning rate of matt fluorocarbon coatings by 75%. Hydrophilic additives' dirt resistance is better. And recoat ability of fluorocarbon coatings modified with the both additives is not affected.The varieties of low surface energy coatings'friction coefficient with surface energy and UV-light irradiation time were investigated. Results show that the surface energy of such coatings increased when exposed under UV-light, so did their static friction coefficient. Nevertheless, their dynamic friction coefficient had not changed obviously under the same condition. The possible reason of that might be that the influence of coatings'smoothness on their dynamic friction coefficient was higher than that of coatings'surface energy.The flow reduction effects of coatings with different varieties and surface topography were compared each other with specially self-made flow resistance test equipment. And theoretical analyses were given to explain the cause of these different effects. Flow resistance tests proved that flow reduction rate of the low surface energy coatings prepared reached above 20%.According to the requirements of cavitation erosion resistance for coatings, a new coating system made up of a bottom layer with high binding strength, an intermediate layer with high toughness and an elastomeric top finish with good cavitation erosion resistance was developed. Its cavitation erosion resistance was compared with that of other coatings including organic coatings and cemented carbide coatings and high-strength steel. Under the condition of fine binding strength, the coating system developed had better cavitation erosion resistance than cemented carbide coating. To meet large thin wall parts'requirements of cavitation erosion resistance, a design scheme of a composite coating system made up of a thermal spraying cemented carbide coating as bottom coat and an elastomeric organic top finish was discussed. The discuss result shows that such composite coating system may have better cavitation erosion resistance than both single elastomeric organic coating system and single thermal spraying cemented carbide coating system.A new kind of two-component solvent-free thick paste curing reaction epoxy coating material modified with phenoxy resin was developed, and the effects of the phenoxy resin on coating material's performance were investigated. A new centrifuging and self-leveling technique for the application of organic thick coating to inner wall of pipes has been successfully developed. A set of special paint coating equipment for preparing thick organic coatings on the inner wall of pipes with centrifuging and self-leveling technique and corresponding tooling and jigs were designed and manufactured. A precision control for the application of developed coating to inner wall of large pipes became true. The thickness of the coating obtained by only one application could reach 2mm, and its dimensional precision, geometric tolerance and surface roughness could reach a high level of precision machining.For the requirements of natural gas pipeline transportation, effects of drag reduction of the developed coating prepared on inner wall of gas pipeline were calculated and compared to that of coating-free pipeline and the commercial epoxy coatings prepared on inner wall of gas pipelines. Results show that the effects of drag reduction of the developed coating are better than that of the commercial epoxy coatings for their application to gas pipeline. |
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