【作者】 王芳；

【导师】 鲁玉祥；

【作者基本信息】 中国石油大学(华东) ， 材料科学与工程， 2015， 硕士

【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。更多还原

【Abstract】 With the implementation of "Deep strategy" of China’s offshore oil industry,the exploration and exploitation of seabed resources need to make use of new instruments.However,the deep ocean has a very unique corrosive environment.Compared with the organic coatings,thermal sprayed Zn coating,Al coating and ZnAl coating further improve the anticorrosion performance of steel structure.Arc is one of the thermal sprayed coating technology,which has been successfully applied in the field of corrosion protection.There are few domestic reports so far for corrosion property and mechanism of arc sprayed coatings in deep-ocean environment and systematic research is still not enough.Meanwhile,The few research data of deep-ocean corrosion abroad remained confidential and rarely made public,as most of the studies are involved in the military field.In this paper,corrosion mechanism of Zn coating,Al coating and ZnAl alloy coating in simulated deep-ocean environment were studied,contrasting which in simulated shallow-sea environment.This paper also used metallographic microscope,stereoscopic microscope,X-ray diffraction,indoor corrosion bolts combined with electrochemical measurement to study the corrosion morphology、corrosion products and corrosion electrochemical performance of the coatings.Morphology observation and analysis of the porosity showed that porosity of Zn coating,Al coating and ZnAl coating were about 2.67%,7.2%,4.03% on average,repectively.In general,the coatings accorded with quality standards of thermal sprayed coatings.After immersion,the morphology and components of corrosion product covering on the coatings were analyzed by stereoscopic microscope and XRD.The results showed that,in simulated deep-ocean environment,there was relatively few corrosion products and the corrosion products cannot completely cover the coating surface.The coatings presented uniform corrosion morphology.The coatings were all of oxygen corrosion.Corrosion products of Zn coating was principally Zn5(OH)8Cl2·H2O,whicn is granular,loose and diffluent;Corrosion products of Al coating was flocculent Al(OH)3,which was not easy to dissolve in seawater;Zn5(OH)8Cl2·H2O and Zn0.7Al0.3(OH)2(CO3)0.15·xH2O were corrosion products of ZnAl coating comaparatively.While in the simulated shallow-sea environment,the coating surface was completely covered by a large number of white corrosion products.Results of corrosion potential of and potentiodynamic polarization curves showed that the coatings were able to provide effective sacrificial anode protection for the matrix in the deep ocean as corrosion potential of the coatings was always lower than that of Q235.Besides,Ecorr and potentiodynamic polarization curves of Zn coating and ZnAl coating were very close.Corrosion mechanism of coatings was understood through the analysis of electrochemical testing combined with corrosion morphology and corrosion products.In the simulated deepocean environment,generally speaking,as the temperature was much lower,electrochemical corrosion resistance was bigger and corrosion rate i obviously lower than that in simulated shallow-sea environment;As oxygen content was less,corrosion products was also less and have weak closed effect for coating porosity,corrosion rate was slightly lower in the immersion process.更多还原