| 油船货油舱用金钢耐蚀性研究 | |
| 郝雪卉 | |
| Subtype | 硕士 |
| Thesis Advisor | 董俊华 |
| 2012 | |
| Degree Grantor | 中国科学院金属研究所 |
| Place of Conferral | 北京 |
| Degree Discipline | 材料工程 |
| Keyword | 货油舱 船板钢 耐蚀性 干湿交替 浸泡 Cargo Oil Tank Shipbuilding Steel Corrosion Resistance Alternating Wet And Dry Immersion |
| Abstract | "现有的油船货油舱（COT）用钢大部分是传统的AH32、AH36级别高强船用钢板，虽然能够满足建造和使用过程中的强度、韧性及焊接性能要求，但在服役过程中这些钢板的耐腐蚀性能较差，引发油船货油舱的高度腐蚀，从而威胁油船运输的安全。因此，研制出既具有良好耐COT环境腐蚀性能，且满足各项性能要求的耐蚀钢意义重大。 本文选用一种传统船板钢（记为1#钢）和三种新型船板钢（分别记为2#、3#、4#钢）为实验材料，通过腐蚀实验分别模拟了船板钢在油船货油舱上甲板和舱底板腐蚀环境中的腐蚀过程，并采用失重测量、XRD、SEM、EPMA等分析方法，深入分析了船板钢的腐蚀行为，锈层组成、结构和性质，以及船板钢的耐蚀性及其影响因素，阐明了船板钢的腐蚀机理，了解了影响其耐蚀性的因素，为获得满足各项性能要求的耐蚀钢材料提供一定的数据支持和理论依据。 在模拟货油舱上甲板腐蚀过程的实验中，钢的腐蚀损失量CL与时间t之间较好地满足指数关系，并得到三种新型船板钢25年后的腐蚀损耗（ECL）的数值。三种新型船板钢的ECL值相差不大，但都超过了《油船货油舱耐蚀钢性能标准》中规定的数值，因此三种钢都不是符合标准的货油舱上甲板用钢。在模拟实验中，船板钢表面会形成冷凝水膜，而且混合气体中含有的酸性气体使得冷凝水膜的pH值降低，从而发生了复杂的电化学腐蚀，最终形成了主要由S、FeS、α-FeOOH、FeCO3及Fe3O4等组成的腐蚀产物。由锈层形貌观察结果表明，腐蚀初期钢表面难以生成致密锈层，经过98天的腐蚀后，腐蚀产物逐渐转化为具有保护性的致密锈层。 四种船板钢在货油舱舱底板的腐蚀实验表明，2#钢的平均年腐蚀速率最小，是符合标准的耐蚀性最好的钢种，而4#钢的平均年腐蚀速率最大，且超过标准中的规定，是耐蚀性最差的钢种。在模拟货油舱舱底板腐蚀实验中，船板钢的腐蚀与其表面珠光体分布及所占面积分数有关，珠光体中电位差较大的片层状渗碳体和铁素体易形成腐蚀微电池，导致其中的铁素体不断溶解而发生腐蚀，因此，钢表面的珠光体优先腐蚀，且珠光体所占面积分数越大，腐蚀速度也越快。此外，钢表面的珠光体区域发生腐蚀后有C富集，从而造成钢的腐蚀速度随浸泡时间的延长而加速。 在模拟货油舱舱底板腐蚀实验中，《油船货油舱耐蚀钢标准》规定用浸泡72h的平均失重结果来推测耐蚀钢一年的减薄深度，这种评价钢板耐腐蚀性能的方法可能存在一定的局限性。因为，此方法往往造成获得的平均腐蚀速度数据离散，误差较大。此外，腐蚀过程中表面积C造成的电偶腐蚀加速也会持续影响平均腐蚀速度的大小，这取决于积C在钢表面覆盖的速度和所占的面积分数。" |
| Other Abstract | "Most of the existing steels for cargo oil tanks (COT) of oil tankers are traditional -AH32and AH36 level-high strength ship plates. Generally speaking, they can meet the demand for strength, toughness and weldability in the process of construction and use, but corrosion resistance of ship plates is too poor in the service process to lead to a high degree of corrosion of COT of oil tankers, thus threaten the safety of tanker transportation. Therefore, it’s of great importance to develop corrosion resistant steel that can be used in the COT corrosive environment, and meet the performance requirements. The paper selected a traditional shipbuilding steel (denoted as the 1# steel) and three new ship plate steel (denoted as 2#, 3#, 4#steel) as the experimental material, and used corrosive experiment to simulate the corrosion process of shipbuilding steel in corrosion environment inside COT. The corrosion behavior of the steel, and the composition, structure and nature of rust layer, as well as the corrosion resistance of shipbuilding steel and its influencing factors were investigated through weight loss measurement, XRD, SEM, EPMA and other analysis techniques in order to illustrate the corrosion mechanism of steel, and understand the factors that have impacts on its corrosion resistance, finally provide certain data support and theoretical basis for getting the anti-corrosion steel which meets the performance requirements. The results from the corrosive experiment of the upper deck showed that there was an exponential relationship between the corrosion loss of CL and time t, and the values of ECL, which represented the corrosion loss after 25 years, of three new kinds of shipbuilding steels were calculated from the corrosion loss. Their values of ECL were found to be similar, but more than the value specified in the , therefore, three new kinds of shipbuilding steel were not appropriate upper deck steel for COT. In the corrosive experiment, condensation water film was formed on the steel surface, and acid gases contained in the mixture gas made the film have a lower pH, which caused the occurrence of the complicated electrochemical corrosion, and eventually corrosion products mainly composed of S, FeS, α-FeOOH, FeCO3 and Fe3O4 were formed on the steel surface. The analysis results of morphology showed that during the initial corrosion, a dense rust layer was hard to be formed on the steel surface, however, corrosion products were gradually transformed into the dense protective rust layer after corrosion of 98 days. During the corrosive experiment of the steel in the bottom environment of COT, the results that contrasted the corrosion resistance of four kinds of steel showed that 2# steel had the smallest average annual corrosion rate, and was the best corrosion resistance steel which meets the standard, while the average annual corrosion rate of 4# steel was the largest, which exceeded the standard provisions, and therefore 4# steel was the worst corrosion resistant steel. In the simulated corrosive experiments of the bottom plate, corrosion rate of shipbuilding steel was found to be related to the distribution and area fraction of pearlite on its surface. Lamellar cementite and ferrite inside pearlite, with different potential, are easy to form corrosion micro-battery, resulting in the ferrite continuously dissolving and corroding, therefore, the pearlite on the steel surface is preferentially corroded, and the larger the area fraction is , the faster corrosion is. In addition, carbon was enriched in pearlite area on the steel surface after immersion, which caused the corrosion rate increased with the immersion time. In the corrosive experiment of the steel in the bottom environment of COT, there may be some limitations in the method that evaluate corrosion resistance of steel plate, which uses the average weight loss after 72h immersion to speculate thinned depth per year of corrosion resistant steel under the standard. Because this method often results that the average corrosion rate scatters and has big error. In addition, the accelerated galvanic corrosion caused by enriched carbon in the corrosion process will continue to affect the average corrosion rate, which depends on the covered speed and the area fraction of product C on the steel surface." |
| Document Type | 学位论文 |
| Identifier | http://ir.imr.ac.cn/handle/321006/64545 |
| Collection | 中国科学院金属研究所 |
| Recommended Citation GB/T 7714 | 郝雪卉. 油船货油舱用金钢耐蚀性研究[D]. 北京. 中国科学院金属研究所,2012. |
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