电弧喷涂Zn、Al、ZnAl涂层在模拟深海环境下的腐蚀行为研究

发布时间：2019-03-15 12:30

【摘要】：随着我国海洋石油工业“深水战略”的实施,开发海底资源需要制造和使用新型仪器和设备。然而,深海具有非常独特的腐蚀环境,海水腐蚀性较强。热喷涂Zn、Al及其合金涂层技术相较于有机涂层,能够使钢铁结构的防腐性能得到进一步提高,其中,电弧喷涂作为热喷涂技术之一,在腐蚀防护领域已经得到了成功的运用。目前国内对于电弧喷涂牺牲阳极涂层在深海环境中腐蚀性能、规律和影响因素迄今报道较少,尚缺少系统研究。同时,深海环境的研究大多涉及军事领域,国外为数不多的研究也是资料保密,极少公开。本文以电弧喷涂Zn涂层、Al涂层、ZnAl合金涂层为研究对象,采用金相显微镜、体视显微镜、X射线衍射技术、室内腐蚀挂片与电化学测试相结合的方法,研究并对比分析了涂层在模拟浅海及深海海水中的腐蚀形貌、腐蚀产物及腐蚀电化学性能随时间的变化规律,从而获得涂层在模拟深海环境下的腐蚀机理。对涂层进行宏观形貌观察及截面微观形貌的金相分析的结果表明,Zn涂层平均孔隙率为2.67%左右;Al涂层平均孔隙率为7.2%左右;ZnAl涂层平均孔隙率约为4.03%,介于Zn涂层和Al涂层孔隙率之间。三种涂层总体来说符合热喷涂涂层的质量标准。对涂层在模拟海水环境下的腐蚀形貌及腐蚀产物(XRD)进行分析,在模拟深海腐蚀环境下,涂层表面腐蚀产物相对较少,不能完全覆盖表面,涂层在海水环境下呈现出均匀腐蚀的腐蚀形貌。三种涂层腐蚀过程为吸氧腐蚀。Zn涂层表面为点状腐蚀产物Zn5(OH)8Cl2·H2O,质地疏松;铝涂层腐蚀产物为絮状Al(OH)3,不易溶解于海水中;锌铝涂层腐蚀产物主要为Zn5(OH)8Cl2·H2O及Zn0.7Al0.3(OH)2(CO3)0.15·x H2O(Zn和Al的复合化合物)。而在模拟浅海腐蚀环境下,涂层表面完全被白色腐蚀产物覆盖,腐蚀产物较多。对涂层在模拟深海中的自腐蚀电位曲线及动电位极化曲线进行研究发现,三种涂层自腐蚀电位始终低于Q235的电位,能够为基体提供有效保护。锌铝涂层在海水中自腐蚀电位及动电位极化曲线与电弧喷涂锌涂层的曲线十分接近。对涂层在模拟深海及浅海环境下的腐蚀电化学行为进行对比,同时结合腐蚀形貌及腐蚀产物分析,了解到涂层在模拟深海环境的腐蚀机理。总体来说,在模拟深海环境下,温度较低,电化学腐蚀阻力较大,腐蚀速率明显低于模拟浅海环境下的腐蚀速率;含氧量较少,腐蚀产物较少,对涂层孔隙具有微弱的封闭作用,腐蚀速率在浸泡过程中略有降低。
[Abstract]:With the implementation of deepwater strategy in China's offshore petroleum industry, the development of submarine resources requires the manufacture and use of new instruments and equipment. However, the deep sea has a very unique corrosive environment, and the seawater is more corrosive. Compared with organic coating, thermal spraying Zn,Al and its alloy coating technology can further improve the corrosion resistance of steel structure. As one of the thermal spraying techniques, arc spraying has been successfully used in corrosion protection field. At present, the corrosion behavior, regularity and influencing factors of arc spraying sacrificial anode coating in deep sea environment are less reported, and there is still no systematic research on the corrosion performance of arc spraying sacrificial anode coating in deep sea environment. At the same time, the deep sea environment research mostly involves the military field, the few foreign research is also confidential, rarely public. In this paper, arc sprayed Zn coating, Al coating and ZnAl alloy coating were used as research objects. Metallographic microscope, stereoscopic microscope, X-ray diffraction technique, indoor corrosion coating and electrochemical test were used. The corrosion morphology, corrosion products and corrosion electrochemical properties of the coatings in simulated shallow sea and deep sea water were studied and compared with each other. The corrosion mechanism of the coatings in simulated deep sea environment was obtained. The results of macro-morphology observation and metallographic analysis show that the average porosity of Zn coating is about 2.67%, the average porosity of Al coating is about 7.2%, and the average porosity of the coating is about 2.67%, and the average porosity of the coating is about 7.2%. The average porosity of ZnAl coating is about 4.03%, which is between Zn coating and Al coating. The three coatings generally meet the quality standards of thermal spraying coatings. The corrosion morphology and corrosion product (XRD) of the coating in simulated seawater environment were analyzed. Under the simulated deep sea corrosion environment, the corrosion products on the coating surface were relatively few, and the coating surface could not completely cover the surface. The coating exhibits uniform corrosion morphology in seawater environment. The corrosion process of the three coatings is oxygen absorption corrosion. The surface of Zn coating is a spot corrosion product Zn5 (OH) 8Cl2 路H2O, which is loose in texture, while the corrosion product of aluminum coating is flocculant Al (OH) 3, which is not easy to dissolve in seawater. The corrosion products of Zn-Al coating are mainly Zn5 (OH) 8Cl2 路H 2O and Zn0.7Al0.3 (OH) 2 (CO3) 0.15 路x H 2O (compound of Zn and Al). But in the simulated shallow sea corrosion environment, the coating surface is completely covered by white corrosion products, corrosion products are more. The self-corrosion potential curves and potentiodynamic polarization curves of the coatings in simulated deep sea were studied. It was found that the self-corrosion potentials of the three coatings were always lower than those of Q235, which could provide effective protection for the substrate. The curves of self-corrosion potential and potentiodynamic polarization of Zn-Al coating in seawater are very close to those of arc sprayed zinc coating. The corrosion electrochemical behavior of the coating in simulated deep sea and shallow sea environment was compared. Combined with the corrosion morphology and corrosion product analysis, the corrosion mechanism of the coating in simulated deep sea environment was found out. Generally speaking, in the simulated deep sea environment, the temperature is lower, the electrochemical corrosion resistance is larger, and the corrosion rate is obviously lower than the simulated shallow sea environment. Less oxygen content and less corrosion products have a weak sealing effect on the pores of the coating, and the corrosion rate decreases slightly in the process of immersion.
【学位授予单位】：中国石油大学(华东)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG174.4

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