摘 要

海洋经济在国民经济版图中占据重要地位，而海洋腐蚀损失是制约海洋经济发展的最大阻碍。随着海洋腐蚀的研究深入，人们将微生物腐蚀(MIC)作为海洋生物腐蚀的研究核心。硅藻广泛存在于海洋环境中，基于海洋环境下的生物膜理论，硅藻在生物膜的形成和以及腐蚀过程中的作用不可忽视。然而，人们主要将海洋生物腐蚀研究集中在各类微生物上，以及由此衍生出的腐蚀防治措施。因此，有必要对硅藻作用下的典型海洋工程用钢的腐蚀进行研究，揭示其腐蚀机理。

本文以船用钢板的常用材料Q235钢与三角褐指藻(P. tricornutum)作为研究对象，以研究典型的海洋硅藻对船用钢板所造成的生物腐蚀特性，分析其影响规律与腐蚀机理。主要结果如下：

⑴P. tricornutum的代谢速度随光强的增加而增加（在一定范围内），EPS产量随之增加；

⑵根据藻细胞附着原理，P. tricornutum在Q235钢表面的附着速率与光强没有直接相关，但由于光强的增加会导致藻细胞EPS的产量增加，EPS的特殊结构会提供给藻细胞以更多的附着机会，附着与表面的藻细胞又作为EPS的生产者，如此过程持续循环，藻细胞的附着速率会随着表面生物膜的形成过程不断提高。

⑶P. tricornutumy因光合作用产生氧气，令Q235钢表面的氧浓度大幅增加，加速了表面氧化膜的形成，表现在开路电位上，开路电位的负移程度降低；

⑷因P. tricornutum的附着和代谢而形成的生物膜会增加Q235钢表面的阻抗值，增加了电荷转移的难度，在这一维度上降低了Q235钢的电化学腐蚀机进程；

⑸由于金属锈层和基体金属的热膨胀率不同，当锈层到达一定厚度，必然会出现破裂。在P. tricornutum的作用下，表面氧化膜的形成速度增加，锈层破裂被提前，Q235钢表面即形成腐蚀微电池，诱发了局部腐蚀，并且随着P. tricornutum的生长繁殖和代谢作用，促进了Q235钢表面的电荷转移过程，Q235钢阻抗值降低，腐蚀加剧。

关键词：Q235钢；微生物腐蚀；三角褐指藻；硅藻腐蚀机理；电化学分析

Abstract

Marine economy occupies an important position in the national economic map, and Marine corrosion loss is the biggest obstacle to the development of Marine economy. With the development of Marine corrosion research, microbial corrosion (MIC) has been regarded as the core of Marine corrosion research. Diatoms exist widely in the Marine environment. Based on the theory of biofilm in the Marine environment, the role of diatoms in the formation and corrosion of biofilms cannot be ignored. However, the research on Marine biological corrosion mainly focuses on various microorganisms and the corrosion prevention measures derived from them. Therefore, it is necessary to study the corrosion mechanism of typical Marine engineering steel under the action of diatoms.

In this paper, the commonly used material of Marine steel plate Q235 steel and
P. tricornutum are taken as research objects to study the biological corrosion characteristics caused by typical Marine diatoms on Marine steel plate, and to analyze its influence rule and corrosion mechanism. The main results are as follows:

⑴The metabolic rate of P. tricornutum increased with the increase of light intensity (within a certain range), and the EPS yield increased accordingly;

⑵According to the principle of algal cell adhesion, the adhesion rate of P. tricornutum on the surface of Q235 steel was not directly related to the light intensity. As the increase in light intensity would lead to an increase in EPS production of algal cells, the special structure of EPS would provide algal cells with more adhesion opportunities, and the algal cells attached to the surface would act as the producers of EPS. Such a continuous cycle would lead to an increase in the adhesion rate of algal cells along with the formation of surface biofilms;

⑶P. tricornutum produces oxygen through photosynthesis, which greatly increases the oxygen concentration on the surface of the sample and accelerates the formation of surface oxide film;

⑷The biofilm formed by P. tricornutum attachment and metabolism will increase the impedance of Q235 steel surface, increase the difficulty of charge transfer, and reduce the electrochemical etching process of Q235 steel in this dimension;

⑸Due to the difference of thermal expansion rate between the metal rust layer and the base metal, when the rust layer reaches a certain thickness, it is inevitable to break. Under the action of P. tricornutum, the formation rate of surface oxide film increases, and the rust layer is broken ahead of time, and the surface of Q235 steel forms corrosion microcells, which induces local corrosion. Moreover, with the growth, reproduction and metabolism of P. tricornutum, the process of charge transfer on the surface of Q235 steel is promoted, and the impedance of Q235 steel decreases and the corrosion intensify.

Key word: Q235 steel; Microorganism influenced corrosion (MIC); P. tricornutum;
Diatom corrosion mechanism; Electrochemical analysis

目录

第 1 章 绪论 1

1.1 引言 1

1.2 国内外研究进展 3

1.3 选题依据与研究内容 6

1.3.1 选题依据 6

1.3.2 研究内容 7

第 2 章 硅藻腐蚀研究的基本理论 8

2.1 海洋生物腐蚀基本理论 8

2.1.1 海洋生物腐蚀概述 8

2.1.2 生物膜的定义与形成过程 9

2.2 海洋硅藻概述 10

2.2.1 硅藻的分类及形貌特征 10

2.2.2 硅藻的胞外多聚物(EPS) 11

2.3 三角褐指藻(P. tricornutum)的培养方法与生长特性 11

2.3.1 P. tricornutum的采集与培养 11

2.3.2 环境因子对P. tricornutum生长特性的影响 12

2.3.3 营养盐对P. tricornutum生长特性的影响 13

2.4 电化学测量应用于腐蚀检测中的基本原理 15

2.4.1 开路电位的测量与应用 15

2.4.2 极化曲线的测量与应用 15

2.4.3 阻抗谱的测量与应用 16

第 3 章 硅藻对船用钢板的腐蚀特性分析 17

3.1 引言 17

3.2 实验材料与方法 17

3.2.1 实验材料与设备 17

3.2.2 实验方法 19

3.3 实验结果与讨论 20

3.3.1 P. tricornutum贴附与腐蚀产物形貌观察 20

3.3.2 电化学测试结果 22

3.3.3 基体的腐蚀形貌 29

3.4 光照条件下P. tricornutum对Q235钢的腐蚀机理 31

第 4 章 结论与展望 32

4.1 结论 32

4.2 展望 32

参考文献 34

致谢 37

绪论

引言

针对海洋环境的腐蚀研究有着重要的经济意义。根据国家发展改革委、自然资源部最新发布的《中国海洋经济发展报告2019》^[1]，2018年，海洋经济总量达83415亿元，同比增速为6.7%，海洋生产总值占国内生产总值的9.3%，多年来在国民经济中的比重基本稳定，对国民经济增速的贡献率接近10%。然而，据世界腐蚀组织(WCO)估计，全球每年的腐蚀成本约为2.4万亿美元（占全球GDP的3%）^[2]。一般认为，海洋腐蚀损失约占总腐蚀损失的1/3，高于所有自然灾害的总和^[3]。

海洋环境中的船用钢材腐蚀是利用Fe作为电子供体，导致Fe的阳极溶解并使基体发生腐蚀。受到海水温度、含盐度、以及大气温度的影响，金属腐蚀更加严重。腐蚀会降低船用钢结构的强度，缩短船舶使用寿命，同时还会使航行阻力增加，船机的航行特性受到影响。