| With the progress of the economy and society of our country continuously and acceleration of construction pace in traffic engineering, the higher requirements of durability for steel bridges are put forward, efficient construction equipment and long-lasting anti-corrosion coatings system are also being focused upon.In this dissertation, an efficient multi-atomizing arc spraying gun is designed and tested to solve the problems facing by the traditional arc spraying equipment, such as low efficiency, narrow spraying width, low adhesion, uneven thickness and unstable quality of sprayed coating. For the status of lack of domestic research on the sealing coating for arc spraying coating, the formulation of nano-modified epoxy sealing paint is designed as arc spraying coating sealer, the two-step process method of preparation of nano-modified paint is proposed, the sealing and corrosion protection mechanism of arc spraying coating is discussed. The arc spraying nano-sealing composite coating system is firstly designed. Through the synergy action of arc spraying anode metal coatings and nano-sealing organic coatings, the corrosion resistance of the composite coating and its bonding strength are significantly increased, with the characteristics of high coating adhesion, long-life anti-corrosion and low life cycle cost. The composite coating system provided strong technical support for the durability and security of steel bridges, and had important engineering application value.According to the characteristics of large flat of steel box girder fitting for mechanized efficient arc spraying, and through the study of multi-atomizing spraying technology, the efficient multi-atomizing arc spraying gun is firstly developed, and supported with mechanized spraying apparatus to forming the efficient and multi- atomizing arc spraying system. Comparing with traditional arc spraying equipment, the newly developed multi-atomizing arc spraying system has achieved the following goals: the spray current is doubled (up to 700A), the spray rate increases two times (up to 78kg / h), spray width increases two times (effective width up to 140mm), coating adhesion increases 40%, coating thickness distribution is more uniform and coating quality is more stable.The arc spraying coating is porous inherently and needs to be effectively sealed by a high permeability sealing paint. So the nano-modified epoxy sealing paint is put forward to meet the requirements. The surface modification of variety of nano-oxide powders and dispersion technology in the epoxy resin paint are studied. The two-step process to prepare nano-modified epoxy sealing paint is advanced by preparing the nano-material concentrates firstly and then producing the nano-modified paint. The nano-modified epoxy sealing paint and its produce method are applied the patent right (Invention patent publication number: CN 1887992A). Nano-modified epoxy sealing paint has physical and chemical sealing dual role for the arc spraying coating with the advantages and characteristics of low viscosity, good permeability, strong sealing capability, high coating adhesion, compact coating structure and good corrosion resistance, etc. The two-step process method of preparing nano-modified paint brings upgrade of traditional protective paint industries, and provides a reasonable means of industrial protective paint production and change of paint production technology.The physical and chemical sealing dual role mechanism of nano-modified epoxy sealing paint for the arc spraying coating is analyzed by experimental research. Corrosion resistance mechanism of arc spraying nano-sealing composite coating is discussed by electrochemical impedance spectroscopy (EIS). Nano-particles can improve the permeability of sealer by fully penetrating into the porous of arc sprayed coating. The sealing coating is dense, and coating adhesion with substrate is increased, with a good physical isolation sealing effect. The sealer pigment could make chemical reaction with arc sprayed Zn/Al coating, and generating the phosphate passive film with good corrosion resistance. Not only the porous of arc spraying coating is better sealed, but also the adhesion and corrosion resistance of the composite coating is further enhanced. The electrochemical properties of the coating and corrosion protection for the substrate are improved by adding nano-materials to sealing paint.According to the requirements of long-life anti-corrosion and durability for steel bridge, the arc spraying nano-sealing composite coating system is firstly designed and applied the patent right (Invention patent publication number: CN 101451243A). Not only the best synergistic effect would be formed by the joint protection of arc spraying metal coating and organic nano-modified sealing coatings, but also the corrosion resistance and the bonding strength of composite coating system could be significantly improved. The composite coating system provides strong technical support for the durability and security of steel bridge by the advantages of high coating adhesion, long-life corrosion protection and low life cycle cost, and also be applied successfully on some large-scale steel bridges. There are very good actual engineering application value and important scientific significance.
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