海洋环境中微藻与钙质层对Q235碳钢腐蚀行为的影响

发布时间：2018-03-23 02:24

本文选题：阴极保护　切入点：Q235碳钢　出处：《江苏科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：钢铁材料因其低廉的价格及优良的性能而被广泛应用于海洋构筑物中,但易发生腐蚀,这将导致严重的后果和巨大的损失。现常用防腐技术主要包括防腐涂层和阴极保护,在实施阴极保护的过程中,材料表面形成一层钙质层,对溶解氧形成一道扩散阻挡层,增加对金属的保护效果。然而海洋中还存在大量的污损生物,钢结构表面的钙质沉积层不可避免的会受到污损生物的影响,同时钙质层也会对污损生物在材料表面的附着产生影响。现今,海洋生物对阴极保护的效率的影响已经被广泛研究,但是生物和钙质层间的相互关系却很少有研究。因此通过此次研究,旨在进一步深入了解阴极保护钙质层与微生物附着之间的相互作用,探讨Q235碳钢表面沉积钙质层后在微藻环境中的腐蚀行为,为海洋金属保护提供理论基础。本文在实验室条件下,采用恒电流极化法在Q235碳钢表面沉积一层钙质层,并与Q235裸钢相比较,通过荧光显微技术研究钙质层对微藻附着的影响,表面分析技术和电化学测试技术研究两者在海水中和微藻环境下的腐蚀行为。在实验室中采用恒电流极化法在Q235碳钢表面沉积钙质层,结果发现,在-30μA/cm2条件下沉积72h得到的钙质层晶体颗粒小且致密,均匀覆盖在基体表面,通过电化学测试得到此时的钙质层对基体材料的保护效果最好。随着沉积时间的增加,电极电位逐渐负移,72h之后逐渐达到析氢电位,导致析氢反应的发生,钙质层发生鼓包开裂现象,对基材保护作用减弱。荧光显微实验表明,微藻在材料表面的附着与固体表面的性质、微藻的活性及密度相关。Q235碳钢为活性金属,表面的腐蚀产物不断更新,不利于微藻的附着;钙质层覆盖在基体表面相当于无机涂层,促进微藻的附着;且微藻密度和活性高有助于在固体表面的粘附。对材料的表面腐蚀形貌观察发现,钙质层与微藻的共同作用可以对基体材料起到最好的保护效果,试样表面划痕清晰,只有轻微的腐蚀;而钙质层在海水中的保护效果不明显,Q235碳钢在微藻环境,试样表面出现大的腐蚀坑洞。微藻主要通过改变环境中溶解氧的含量来影响金属的电化学行为,其主要特征为:金属在含藻体系中的开路电位随浸泡时间的变化与光照有关,在有光照条件下,金属的开路电位随光照时间的增加而逐渐负移,在无光照时随着时间的延长开路电位正移,表现出与光照有关的振荡关系。研究Q235碳钢和钙质层试样在微藻环境中的腐蚀行为,在含藻体系中微藻的光合作用使溶液中氧气含量升高,阴极氧去极化作用增强,使材料的腐蚀速率升高。钙质层试样在无藻环境中,钙质层的不均匀性形成氧浓差电池,加速腐蚀速度,造成材料的局部腐蚀。钙质层与生物膜共同形成的复合膜结构较为致密且与基体的结合力好,能够抑制电荷的传递和氧气向基体表面扩散,抑制金属的腐蚀。
[Abstract]:Iron and steel materials are widely used in marine structures because of their low price and excellent performance, but they are prone to corrosion, which will lead to serious consequences and huge losses. At present, the common anticorrosive technologies mainly include anticorrosive coatings and cathodic protection. In the process of cathodic protection, a layer of calcium is formed on the surface of the material, and a diffusion barrier layer is formed on the dissolved oxygen. Calcium deposits on steel structures will inevitably be affected by fouling organisms, and calcium layers will also have an impact on the adhesion of fouling organisms on the surface of materials. The effects of marine life on the efficiency of cathodic protection have been extensively studied, but little has been done on the relationship between biological and calcium layers. In order to further understand the interaction between cathodic protection calcareous layer and microbial adhesion, the corrosion behavior of Q235 carbon steel after deposition of calcium layer in microalgae environment was discussed. In this paper, a layer of calcium layer was deposited on the surface of Q235 carbon steel by constant current polarization method under laboratory conditions, and compared with that of Q235 bare steel, the effect of calcium layer on the adhesion of microalgae was studied by fluorescence microscopy. Surface analysis and electrochemical measurement techniques were used to study the corrosion behavior of both in seawater and microalgae environment. The calcareous layer was deposited on Q235 carbon steel by constant current polarization method in laboratory. The crystals of calcareous layer deposited at -30 渭 A/cm2 for 72 hours were small and compact, and they were uniformly covered on the substrate surface. The results of electrochemical test showed that the calcium layer had the best protective effect on the matrix material with the increase of deposition time. The electrode potential gradually reached the hydrogen evolution potential after 72 hours of negative shift, which led to the occurrence of hydrogen evolution reaction, the formation of bulging cracking in the calcium layer, and the weakening of the protective effect on the substrate. The adhesion of microalgae on the surface of the material is related to the properties of the solid surface. The activity and density of microalgae. Q235 carbon steel is the active metal, the corrosion products on the surface are constantly updated, which is not conducive to the adhesion of microalgae, and the calcium coating is equivalent to inorganic coating on the substrate. The high density and activity of microalgae contribute to the adhesion on the solid surface. The surface corrosion morphology of the material shows that the interaction of the calcium layer and the microalgae can provide the best protective effect on the matrix material. The scratch on the surface of the specimen was clear and only slightly corroded, while the protective effect of the calcareous layer in the seawater was not obvious compared with that of the Q235 carbon steel in the microalgae environment. There are large corrosion holes on the surface of the sample. Microalgae affect the electrochemical behavior of metal mainly by changing the content of dissolved oxygen in the environment. Its main characteristics are that the open circuit potential of metal in the algae-containing system changes with the immersion time and is related to the light. Under the condition of light, the open circuit potential of the metal gradually shifted negatively with the increase of the illumination time, and the open circuit potential shifted positively with the prolongation of the time when there was no light. The corrosion behavior of Q235 carbon steel and calcareous layer samples in microalgae environment was studied. The photosynthesis of microalgae in algae-containing system increased the oxygen content and the cathodic oxygen depolarization in the solution. Increase the corrosion rate of the material. In the algae-free environment, the non-uniformity of the calcareous layer forms oxygen concentration cell, which accelerates the corrosion rate. The composite membrane formed by calcareous layer and biofilm has a compact structure and good adhesion to the substrate, which can inhibit the transfer of charge and the diffusion of oxygen to the surface of the substrate, as well as the corrosion of metals.
【学位授予单位】：江苏科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG172

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