海洋环境跃变区碳钢腐蚀行为与机理研究

发布时间：2018-12-19 11:32

【摘要】：在海洋环境中存在众多的界面,如海水-海气交换界面、海水-海泥交换界面、海洋温跃层等,在界面两侧体系中环境因子相差较大,形成环境跃变区。在环境跃变区,化学反应速度、反应机理与本体体系相差较大,引起众多科研工作者的关注与研究兴趣。海洋环境使用的金属材料,处于或贯穿海洋环境的跃变区。研究者针对海洋环境跃变区金属的腐蚀研究仅局限于海水-海气跃变区,很少涉及海水-海泥跃变区金属的腐蚀,更未涉及海洋温跃层金属的腐蚀。本文以海水-海气交换界面、海水-海泥交换界面、海洋温跃层等海洋环境跃变区为环境背景,以碳钢Q235、管线钢x70、螺纹钢HRB400为研究材料,利用改进的阵列电极技术,系统地研究了海洋环境跃变区碳钢的腐蚀行为与机理。研究结果表明,在海水-海气界面区碳钢存在较为严重的腐蚀,垂直海水-海气界面的碳钢存在两个腐蚀电流峰,一个在水线区域,另一个在近海水-海气界面的海水区域。在浸泡初期,碳钢以形成微观腐蚀电池为主；在浸泡实验进行15天后,碳钢以大气区与海水浸没区之间形成宏观腐蚀电池为主。在不同区域,碳钢的腐蚀机理不同,造成腐蚀机理差别的主要原因是溶解氧的浓度差和碳钢表面腐蚀产物的致密性不同。海水-海泥界面区碳钢形成明显的宏观腐蚀电池,阳极区集中在海水-海泥界面下一定距离的海泥区域,海水区为阴极区。阳极与阴极的电流差值较长时间稳定在1000 nA左右。贯穿海水-海泥界面区的碳钢有两个腐蚀电流峰,分别为近海水-海泥界面区的海泥区和远海水-海泥界面区的海水区。海水-海泥界面区碳钢表面腐蚀产物的致密程度与溶解氧呈正相关性。海水-海泥界面区碳钢的腐蚀不单受电位差形成的宏观腐蚀电池作用影响,还受溶解氧浓度、海泥阻抗甚至微生物等其它因素的影响。贯穿模拟海水温跃层的X70钢形成明显的宏观腐蚀电池,在浸泡初期,下部区为阴极,上部为阳极,随着浸泡时间的延长阴阳极发生反转。温跃层不同位置的腐蚀速率不同,温跃层上部的X70钢腐蚀速率高于下部的腐蚀速率,温跃层下部的X70钢腐蚀速率为60 mg·cm-2·y-1,而温跃层上部的X70钢腐蚀速率为100mg·cm-2·y-1。温跃层下部的X70钢的腐蚀主要受宏观腐蚀电池的影响,温跃层上部的X70钢的腐蚀主要受溶解氧的影响。贯穿海水飞溅区、潮差区和全浸区的裸钢筋,在电连接列中,位于海水全浸区与潮差区的界面区钢筋腐蚀速率最大。海水全浸区为阳极,潮差区为阴极,形成宏观腐蚀电池。在非电连接列中,潮差区钢筋的腐蚀速率最大。贯穿海水飞溅区、潮差区和全浸区的裸钢筋,电连接列比非电连接列腐蚀轻,而且腐蚀更均匀。贯穿海水飞溅区、潮差区和全浸区的混凝土中钢筋,发生腐蚀的区域首先发生在海水全浸区,然后移到潮差区,最后到达飞溅区。在模拟海洋环境跃变区中混凝土钢筋的腐蚀由氧扩散和盐渗透联合控制。处于不同模拟海洋环境跃变区的混凝士中盐离子渗透速率和氧扩散速率不同,处于飞溅区的混凝土具有最高的盐离子渗透速率和氧扩散速率：在潮差区和飞溅区,混凝十保护层中氯离子的传输机制是浓差扩散和干湿循环中干燥浓缩共同作用：海水全浸区混凝士保护层氯离子的传输机制是浓差扩散,以上跃变区混凝士中氯离子的传输机制与混凝土中钢筋的腐蚀行为与规律相一致。
[Abstract]:There are many interfaces in the marine environment, such as the sea water-sea-air exchange interface, the seawater-sea mud exchange interface, the ocean temperature jump layer and so on. In the area of environmental jump, the speed of chemical reaction, the reaction mechanism and the body system have a large phase difference, which cause the attention and research interest of many researchers. Metallic materials used in the marine environment, in or throughout the marine environment. The research of the corrosion of the metal in the marine environment of the marine environment is confined to the sea-sea-gas jump area, and the corrosion of the metal in the sea-sea mud jump area is very little concerned, and the corrosion of the metal in the sea-sea-sea-jump area is not involved. Based on the sea-sea-sea-gas exchange interface, the sea-sea mud exchange interface and the marine temperature-jump layer as the environmental background, the carbon steel Q235, the pipeline steel x70 and the screw steel HRB400 are used as the research material, and the improved array electrode technology is utilized. The corrosion behavior and mechanism of carbon steel in the marine environment are studied systematically. The results show that the carbon steel in the seawater-sea-air interface region has serious corrosion, and the carbon steel in the vertical seawater-sea-air interface has two corrosion current peaks, one in the water line area and the other in the seawater area near the sea-sea interface. In the initial stage of the immersion, the carbon steel is dominated by the formation of micro-corrosion cells; after 15 days in the immersion test, the carbon steel is dominated by a macro-corrosion cell formed between the atmospheric region and the seawater immersion region. In different regions, the corrosion mechanism of carbon steel is different, and the main reason for the difference of corrosion mechanism is that the concentration difference of the dissolved oxygen and the compactness of the corrosion products on the surface of the carbon steel are different. The carbon steel in the seawater-sea mud interface area forms a significant macro-corrosion cell, and the anode area is concentrated in the sea mud area at a certain distance under the seawater-sea mud interface, and the seawater area is the cathode area. The current difference between the anode and the cathode is stable at about 1000 nA for a long time. The carbon steel passing through the interface area of the sea-sea mud has two corrosion current peaks, which are the sea mud area of the near-sea-sea mud interface area and the seawater area of the far-sea-sea mud interface area, respectively. The density of the corrosion products on the surface of the carbon steel in the seawater-sea mud interface area is positively related to the dissolved oxygen. The corrosion of the carbon steel in the interface area of the sea-sea mud is not only influenced by the effect of the macro-corrosion cell formed by the potential difference, but also the influence of the dissolved oxygen concentration, the sea mud impedance and other factors. The X70 steel, which runs through the simulated seawater temperature jump layer, forms a clear macro-corrosion cell. In the initial stage of the immersion, the lower zone is the cathode, the upper part is the anode, and the anode and the cathode are reversed with the prolonging of the soaking time. The corrosion rate of X70 steel at the upper part of the temperature-jump layer is higher than that of the lower part. The corrosion rate of X70 steel at the lower part of the temperature-jump layer is 60 mg 路 cm-2 路 y-1, while the corrosion rate of X70 steel at the upper part of the thermocline is 100mg 路 cm-2 路 y-1. The corrosion of X70 steel at the lower part of the thermocline is mainly affected by the macro-corrosion cell, and the corrosion of X70 steel in the upper part of the temperature-jump layer is mainly affected by the dissolved oxygen. The corrosion rate of the steel bars in the interface area of the seawater full-soaking area and the tide-difference area is the largest in the electric connection column through the seawater splash area, the tide difference area and the bare steel bar in the full-dip area. the seawater full-soaking area is an anode, and the tidal zone is a cathode, and a macro-corrosion battery is formed. In the non-electrically connected column, the corrosion rate of the steel bars in the tidal zone is the largest. The bare steel bars passing through the seawater splash area, the tidal zone and the full immersion area, the electrical connection column is less corrosion than the non-electric connecting column, and the corrosion is more uniform. In the concrete of the seawater splash zone, the tidal zone and the full-dip zone, the area of the corrosion occurs first in the seawater full-dip zone and then to the tidal zone and finally to the splash zone. The corrosion of concrete reinforcement in the simulated marine environment is controlled by oxygen diffusion and salt penetration. the rate of the salt ion penetration and the oxygen diffusion rate of the concrete in the jump zone of the different simulated marine environment are different, and the concrete in the splash zone has the highest salt ion penetration rate and the oxygen diffusion rate: in the tidal zone and the splash zone, the transmission mechanism of the chloride ions in the mixed-gel ten protection layer is the co-action of the concentrated difference diffusion and the dry concentration in the dry-wet cycle, The transmission mechanism of the chloride ion in the mixed concrete in the above transition zone is consistent with the corrosion behavior and the law of the steel bar in the concrete.
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG178

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