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作者简介:

夏晓健,男,1988年出生,博士,高级工程师。主要研究方向为腐蚀与防护、新材料应用。E-mail:13247193256@163.com

通讯作者:

杨小佳,男,1989年出生,博士,讲师。主要研究方向为材料腐蚀大数据技术与材料基因工程应用技术,包括系列化的腐蚀传感器开发、数据挖掘和腐蚀预测预警等技术。E-mail:yangxiaojia@ustb.edu.cn

中图分类号:TG172

DOI:10.11933/j.issn.1007-9289.20230710002

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参考文献 8
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参考文献 9
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参考文献 14
WU W,HAO W K,LIU Z Y,et al.Corrosion behavior of E690 high-strength steel in alternating wet-dry marine environment with different pH values[J].Journal of Materials Engineering and Performance,2015,24:4636-4646.
参考文献 15
MA Y T,LI Y,WANG F H.Corrosion of low carbon steel in atmospheric environments of different chloride content[J].Corrosion Science,2009,51(5):997-1006.
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MELCHERS R.Pitting corrosion of mild steel in marine immersion environment-part 1:maximum pit depth[J].Corrosion,2004,60(10):824-836.
目录contents

    摘要

    随着“一带一路”和“海洋强国”等重大战略的深入推进,沿海地区及海上重大装备设施面临着空前严峻的海洋环境挑战。深入研究海洋大气腐蚀行为,对于延缓腐蚀过程、确保设施安全运行以及防止重大安全事故和经济损失具有至关重要的意义。以 Q235 碳钢作为研究对象,基于腐蚀大数据技术,通过周期浸泡加速试验获取实时连续的腐蚀数据,研究环境因子 Cl 、HSO3 及 pH 值对碳钢海洋大气腐蚀行为的影响。结果表明:随着 Cl 、HSO3 浓度的增加或 pH 值的降低,腐蚀累积量呈不断上升的趋势,腐蚀大数据采集结果与碳钢试样腐蚀形貌及锈层分析结果一致。随试验的进行,当 Cl 浓度较低时,锈层朝着更加稳定的方向发展;Cl 浓度较高时,锈层稳定性不断下降。0.05% HSO3 浓度下,腐蚀始终以相对较低的速率匀速进行;浓度为 0.1%时,腐蚀先是匀速进行,但由于腐蚀后期形成了具有一定保护性的锈层,腐蚀速率有所下降;当浓度达到 0.2%时,腐蚀速率在试验后期反而加快,锈层难以维持相对稳定的状态。试验环境 pH=5 或 3 时,整个试验周期的腐蚀速率整体呈下降趋势;pH=1 时,腐蚀速率呈持续上升趋势。腐蚀大数据方法与传统挂片法研究结果具有较高的一致性,验证了腐蚀大数据手段对于环境腐蚀研究的可靠性,研究结果可为后续开展数据分析与挖掘工作奠定基础。

    Abstract

    The “Belt and Road” initiative and the aspiration to evolve into a “Maritime Powerhouse” have highlighted the challenges of marine atmospheric corrosion affecting coastal regions and key maritime infrastructure. This phenomenon presents a critical challenge for the global maritime sector, emphasizing the need for in-depth understanding and effective mitigation strategies to preserve the integrity and operational safety of maritime facilities, thereby preventing significant safety incidents and economic losses. This study focuses on Q235 carbon steel, a material extensively used in maritime constructions, by applying advanced corrosion big data technology. The research methodology incorporates cyclic immersion acceleration tests, enabling the collection of continuous real-time corrosion data. This approach is vital for a comprehensive analysis of the effects of environmental factors such as Cl , HSO3 , and pH levels on the corrosion behavior of carbon steel in marine atmospheres. The findings of this study indicate a clear correlation between increased concentrations of Cl and HSO3 or a decrease in pH levels and the acceleration of the corrosion process. The gathered data aligns with the observed physical corrosion morphology and rust layer analysis of the steel samples, demonstrating the robustness and reliability of the data-driven approach. This study highlights that at lower Cl concentrations, the rust layer tends toward greater stability whereas higher concentrations result in decreased stability. With different HSO3 concentrations, the corrosion behavior varies: at 0.05%, corrosion proceeds at a steady low rate; at 0.1%, a protective rust layer forms, slowing the corrosion rate; and at 0.2%, the rate increases in the later stages, challenging the stability of the rust layer. In environments with pH values of 5 or 3, the overall trend is a decline in the corrosion rates, in contrast to a pH of 1, where the rate consistently increases. A significant aspect of this study is the integration of traditional corrosion research methodologies with modern big data analytics. This innovative approach represents a substantial advancement in corrosion research, combining the proven reliability of traditional methods with the extensive analytical capabilities of modern data science. The consistency of the big data findings with traditional coupon methods validates this approach, highlighting its effectiveness in providing deep and comprehensive insights into environmental corrosion processes. Furthermore, this research utilizes a range of advanced experimental techniques, such as scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), confocal laser scanning microscopy, and various electrochemical tests. These methods have been instrumental in characterizing the morphological and chemical properties of the rust layer, thereby enriching the overall findings of this study. This extensive study provides a detailed examination of marine atmospheric corrosion, contributing significantly to the field by offering new perspectives and robust methodologies. These contributions are crucial for effectively assessing and mitigating corrosion in maritime environments, aligning with international maritime strategies and infrastructure safety objectives. In summary, this study marks a paradigm shift in corrosion research, blending traditional experimental methods with the advanced analytical capabilities of big data. This integration opens new avenues for future investigations and innovations in the field, underscoring the importance of data-driven approaches in understanding and addressing complex environmental challenges. With its comprehensive analysis, innovative methodology, and significant findings, this research not only deepens the understanding of marine atmospheric corrosion but also establishes a solid foundation for future data-driven studies and solutions in maritime engineering and environmental protection. This study is a testament to the power of integrating traditional research methods with modern data analytics to address complex environmental issues, paving the way for further advancements in the field. Additionally, this study underscores the significance of the ongoing technological advancements in corrosion research. As environmental conditions continue to evolve, adapting and refining research methodologies to keep pace with them is becoming increasingly important. The use of big data and advanced analytical techniques in this study not only demonstrates a progressive approach to understanding marine atmospheric corrosion but also serves as a model for future studies in similar fields. This approach highlights the necessity of continuous innovation and adaptation in scientific research, particularly in areas with significant practical implications such as maritime infrastructure and environmental protection. Embracing these innovative methodologies ensures that research remains relevant, effective, and capable of addressing the complex challenges posed by a dynamically changing environment.

  • 0 前言

  • 近年来,随着对海洋资源探索的增加和海上工程的发展,沿海地区及海上重大装备设施面临着空前严峻的海洋环境挑战[1]。海洋大气腐蚀具有高温、高湿及高盐雾等特点,且涉及的环境影响因子繁杂多变[2-6]。进一步研究海洋大气腐蚀行为,实现海洋大气腐蚀行为的精准评估与预测,对于保障装备设施安全运行、防止重大安全事故和经济损失具有重要的意义。

  • 尽管海洋大气腐蚀一直是研究的热点,但现有研究往往受数据收集和处理能力的限制。传统研究模式通常采用挂片法,试验周期长且无法获取连续的试验数据,并且在处理复杂的环境影响因素时存在局限性[7-8]。迫切需要探索新的方法,利用现代科技和大数据分析技术来提高腐蚀行为判断的准确性和效率。近年来,腐蚀大数据技术的出现帮助解决了这一难题。腐蚀大数据技术采用高通量的试验方法,获取海量连续的实时腐蚀数据,动态监测腐蚀进程,可以更准确地研究腐蚀机理[9-10]。而研究传统挂片法与腐蚀大数据技术之间的关联至关重要,是开展后续数据挖掘工作的前提与基础。

  • 本文以 Q235 碳钢作为研究对象,在模拟海洋大气环境下,基于腐蚀大数据、电偶及电阻传感器,通过周期浸泡加速试验,获取实时连续的腐蚀数据,研究环境因子 Cl、HSO3 及 pH 值对海洋大气腐蚀行为的影响。通过分析腐蚀大数据采集结果,包括相对电流强度、腐蚀累积电量及电阻增量变化情况,以捕捉整个腐蚀过程的动态变化过程。采用扫描电子显微镜(SEM,TESCAN Mira 4)、能谱仪(EDS)、激光共聚焦及电化学等试验方法,对周浸后试样的锈层进行分析表征,验证腐蚀大数据与传统挂片法研究结果的一致性,证明腐蚀大数据技术对于环境腐蚀研究的可靠性。

  • 1 试验准备

  • 1.1 试验材料

  • 所用材料为 Q235 碳钢,其具体成分如表1 所示。采用线切割的方式加工为平板试样,试样尺寸为 50 mm×25 mm×3 mm,在试样顶端打孔,直径 2 mm,用于悬挂试样。

  • 表1 Q235 碳钢的化学成分(质量分数 / wt. %)

  • Table1 Chemical composition of Q235 carbon steel (wt. %)

  • 1.2 腐蚀大数据周浸加速试验

  • 将尺寸为50 mm×25 mm×3 mm的Q235试样使用砂纸将各表面从 120~800 cW 逐级打磨,然后用去离子水和酒精清洗表面,并用鼓风机吹干。将试样放置烘箱中烘干,24 h 后对试样进行称重和尺寸测量。

  • 本文采用传统挂片和腐蚀大数据技术相结合的方法,利用自主研发的腐蚀大数据采集器、腐蚀电偶和电阻传感器进行连续的腐蚀数据采集。传感器装置如图1 所示。电偶传感器的工作原理为双电极体系,共包含七对电极片,每片厚度为 1 mm,每对电极片之间用环氧玻纤板材质的绝缘片分隔,绝缘片厚度为 0.1 mm。工作电极为 Q235,使用纯铜作为参比电极及对电极。电阻传感器的电阻丝长度为635 mm,厚度为 1 mm。将制作好的传感器使用环氧密封胶灌封,室温静置 48 h 达到固化效果,固化后使用砂纸从 60~2 000 cW 逐级打磨,并用去离子水和酒精清洗表面后吹干。将腐蚀传感器和挂片试样一同置于周浸试验箱进行周浸试验,传感器采集频率为 1 次 / min。

  • 图1 腐蚀传感器

  • Fig.1 Corrosion sensor

  • 利用多种溶液来模拟不同海洋大气环境,采用 NaCl+NaHSO3 腐蚀溶液模拟海洋大气环境具有较好的相关性[11-13],其中 NaHSO3 的添加及对 pH 的调节用于模拟污染海洋大气环境。溶液成分如表2 所示,其中 pH 值通过稀释的 HCl 调节。试验所用周浸箱为北京科技大学自主研制的 EA-08 型周浸箱,一个干湿循环周期为 60 min,浸润时间为 12 min,干燥时间为 48 min,试验温度为 35±1℃,试验湿度为 98%。周浸试验分为三个周期,分别为 72、168 和 504 h,每个周期周浸试样都准备三个平行试样,以提高试验的准确性。

  • 表2 不同模拟海洋大气环境周浸溶液参数

  • Table2 Parameters of periodic immersion solutions simulating marine atmospheric environments

  • 1.3 腐蚀大数据分析

  • 在周浸加速试验结束时,通过电偶及电阻传感器采集腐蚀数据,计算腐蚀相对电流强度、腐蚀累积电量以及电阻增量变化,分析整个腐蚀的动态变化过程。

  • 1.4 腐蚀失重计算

  • 在每个周期的试验结束时,先取出试样进行除锈,按照《金属和合金的腐蚀——腐蚀试样上腐蚀产物的清除(ISO8407—2009)》标准配制除锈液,成分为 500 mL H2O+500 mL HCl+3.5 g C6H12N4,除锈后使用去离子水和酒精进行清洗,后吹干,随即称重测量并计算腐蚀速率。计算失重和腐蚀速率的公式如下:

  • W=m0-mtS
    (1)
  • v=8.76×104×m0-mtρSt
    (2)
  • 式中,W 为腐蚀失重(g / cm2),m0为试样初始质量(g),mt 为除锈后质量(g),S 为试样暴露的面积(cm 2 ),v 为腐蚀速率(mm / a),ρ 为试样的密度(7.8 g / cm3),t 为试验时间(h)。

  • 1.5 腐蚀产物分析

  • 利用相机对周浸试验后的试样及传感器形貌进行记录,再通过 SEM 观察锈层的截面形貌,使用 EDS 进行锈层元素分布和半定量分析。使用共聚焦激光扫描显微镜(KEYENCE,VK-9700)对试样的 3D 形貌进行表征,并统计分析蚀坑的相关参数。

  • 2 结果与讨论

  • 2.1 不同海洋大气环境的腐蚀大数据采集结果

  • 腐蚀大数据采集器可以实时采集碳钢表面的瞬态腐蚀相对电流强度。腐蚀相对电流强度与碳钢的腐蚀速率成正比,腐蚀相对电流强度越大,碳钢的腐蚀速率越快。图2~4 为周浸试验结束后腐蚀电偶传感器的宏观形貌,可以看出随着 Cl 浓度的升高,电偶传感器的腐蚀程度更加严重。溶液中 HSO3 浓度增大,腐蚀形貌同样不断加剧。在酸性环境中的电偶传感器仍能看见部分基底材料,说明 pH 值降低对锈层的形成产生较大的影响,难以形成稳定锈层,腐蚀产物在低 pH 值时会被溶解,并且腐蚀产物多孔松散[14]

  • 图2 不同 Cl 浓度溶液周浸后腐蚀电偶传感器的宏观形貌

  • Fig.2 Macroscopic morphology of the thermocouple corrosion sensor after periodic immersion in different Cl⁻ concentration solutions

  • 图3 不同 HSO3 浓度溶液周浸后腐蚀电偶传感器的宏观形貌

  • Fig.3 Macroscopic morphology of the thermocouple corrosion sensor after periodic immersion in different HSO3⁻ concentration solutions

  • 图4 不同 pH 值溶液周浸后腐蚀电偶传感器的宏观形貌

  • Fig.4 Macroscopic morphology of the thermocouple corrosion sensor after periodic immersion in different pH solutions

  • 图5~7 为周浸试验后腐蚀电阻传感器宏观形貌,腐蚀程度与电偶传感器规律一致。于 pH 值为 1 的溶液中进行试验的传感器,其基底的电阻丝大部分裸露,没有形成稳定锈层,锈层被完全破坏。

  • 图5 不同 Cl 浓渡溶液周浸后腐蚀电阻传感器的宏观形貌

  • Fig.5 Macroscopic morphology of the resistance corrosion sensor after periodic immersion in different Cl⁻ concentration solutions

  • 图6 不同 HSO3 浓度溶液周浸后腐蚀电阻传感器的宏观形貌

  • Fig.6 Macroscopic morphology of the resistance corrosion sensor after periodic immersion in different HSO3⁻ concentration solutions

  • 图7 不同 pH 值溶液周浸后腐蚀电阻传感器的宏观形貌

  • Fig.7 Macroscopic morphology of the resistance corrosion sensor after periodic immersion in different pH solutions

  • 图8 为不同 Cl 浓度下,碳钢腐蚀电偶传感器在周浸箱中连续试验 3 万 min 的腐蚀相对电流强度的变化曲线及腐蚀累积电量。可以看出,在试验开始时,腐蚀速率较大,但随试验的进行,腐蚀速率很快趋于平稳,并且随 Cl 浓度的增加,腐蚀累积电量不断增大,腐蚀总量不断增加。

  • 当 Cl 浓度较低时,腐蚀速率的变化趋势随着试验的进行不断下降,并且随着浓度升高,这一趋势出现得更快,这可能与锈层的形成、变化及溶解有关[15];Cl 浓度下降,随试验时间的增加,锈层朝着更加稳定的方向发展,锈层对基体的保护性增加,腐蚀相对电流强度不断下降,腐蚀速率也随之减小; 但当 Cl 浓度相对较高时,趋势完全相反,腐蚀速率随着时间的变化而逐渐增大。由于溶液腐蚀性增强,传感器表面难以形成稳定的具有保护性的锈层[16]。 Cl 浓度达到 5%时,腐蚀速率逐渐增大,但在腐蚀后期出现下降的趋势,说明腐蚀后期锈层保护性有所增加。

  • 图8 不同 Cl 浓度溶液周浸后腐蚀相对电流强度及腐蚀累积电量

  • Fig.8 Relative current intensity and accumulated corrosion quantity after periodic immersion in different Cl⁻ concentration solutions

  • 图9 为不同 HSO3 浓度下,碳钢腐蚀电偶传感器的腐蚀相对电流强度的变化曲线及腐蚀累积电量。从腐蚀累积电量可以看出,HSO3 浓度增加导致腐蚀总量上升。试验早期,腐蚀相对电流强度及腐蚀速率的差异并不明显。0.05% HSO3 浓度下,从始至终腐蚀几乎以相对较低的速率匀速进行;浓度为 0.1%时,腐蚀先是匀速进行,在后期,腐蚀速率有所下降,这可能是由于形成了具有一定保护性的锈层[17];但当 HSO3 浓度达到 0.2%时,腐蚀速率在试验后期反而出现了一个陡增的台阶,说明在该环境下,腐蚀传感器的锈层难以维持相对稳定的状态。

  • 图9 不同 HSO3 浓度溶液周浸后腐蚀相对电流及腐蚀累积电量

  • Fig.9 Relative current and accumulated corrosion quantity after periodic immersion in different HSO3⁻ concentration solutions

  • 图10 为不同 pH 值溶液下,碳钢腐蚀电偶传感器的腐蚀相对电流强度的变化曲线及腐蚀累积电量。从腐蚀累积量来看,pH 值的降低会导致腐蚀总量增加。当溶液的 pH=5 时,整个试验周期,腐蚀速率不断下降;pH=3 时,在腐蚀后期,腐蚀速率波动较大; 但当溶液 pH=1 时,腐蚀速率呈持续上升趋势,并且腐蚀相对电流强度没有出现明显的阶梯性变化,说明在该环境下难以形成具有保护性的稳定锈层[18],这也与上述传感器的宏观形貌相对应,试验结束时,电偶传感器仍能观察到部分基体材料暴露。

  • 图10 不同 pH 值溶液周浸后腐蚀相对电流及腐蚀累积电量

  • Fig.10 Relative current and accumulated corrosion quantity after periodic immersion in different pH solutions

  • 图11~13 为腐蚀电阻传感器由于腐蚀造成的减薄导致电阻变化的曲线。图中电阻增量曲线周期性的凸起是由于定期更换周浸溶液,温度降低导致的。由于周浸实验箱温度设定,试验环境的温度很快会恢复至更换溶液前,这种周期性变化对整体试验造成的影响较小。可以看出,所有的电阻增量曲线都是先经过一个较大的波动,再初步稳定,以相对平稳的方式继续腐蚀。如图11 所示,腐蚀速率同样随 Cl 浓度增加而增大。浓度较低时,腐蚀速率呈逐渐缓和的趋势;浓度超过 2%时,腐蚀速率则持续上升,这与腐蚀电偶传感器得出的结论一致。

  • 图11 不同Cl-浓度溶液周浸后腐蚀电阻传感器电阻增量变化

  • Fig.11 Resistance incremental change of resistance corrosion sensor after periodic immersion in different Cl⁻ concentration solutions

  • 图12 为不同 HSO3 浓度下,电阻传感器电阻增量变化曲线,可以看出,浓度较低时,腐蚀速率不断降低;当浓度达到 0.2%时,整个试验周期腐蚀速率无明显降低的趋势,说明生成的锈层不具有足够的保护性。

  • 图12 不同 HSO3 浓渡溶液周浸后腐蚀电阻传感器电阻增量变化

  • Fig.12 Resistance incremental change of resistance corrosion sensor after periodic immersion in different HSO3⁻ concentration solutions

  • 腐蚀总量随 pH 值的降低而增大,pH=3 和 1 时的腐蚀总量没有太大差异,但是腐蚀速率却存在较大差异。pH=3 的环境中,电阻传感器腐蚀速率经历一个由快至慢的变化;而 pH=1 的溶液中,腐蚀速率则不断上升,同样与宏观形貌结果相对应,传感器表面无法形成稳定锈层。

  • 图13 不同 pH 值溶液周浸后腐蚀电阻传感器电阻增量变化

  • Fig.13 Resistance incremental change of resistance corrosion sensor after periodic immersion in different pH solutions

  • 2.2 腐蚀失重分析

  • 利用式(1)计算碳钢在不同环境不同试验周期下的腐蚀速率。图14 为碳钢的腐蚀动力学曲线。从图14a 中可以看出,随着环境中 Cl 浓度的增加,碳钢的腐蚀速率不断加快。随试验的进行,所有 Cl 浓度下的碳钢腐蚀速率都呈下降趋势,其中 3.5% NaCl 环境下碳钢腐蚀速率降低最为显著。

  • 图14 碳钢腐蚀速率曲线及失重曲线

  • Fig.14 Corrosion rate and weight loss curves of carbon steel

  • 图14b 为不同 HSO3 浓度对碳钢腐蚀速率及失重的影响。可以看出随着 HSO3 浓度的增高,碳钢的腐蚀速率不断加快,这说明 HSO3 的添加对碳钢的腐蚀存在促进作用[19]。当 HSO3 浓度达到 0.2% 时,加速腐蚀的效果十分显著。

  • 图14c 为不同 pH 值环境下碳钢腐蚀速率及腐蚀失重曲线。从图中可以看出随 pH 值减小,腐蚀速率逐渐增大。当碳钢暴露在酸性环境中时,H+ 会与碳钢表面的氧化物反应,导致碳钢表面的锈层被破坏,从而加速碳钢的腐蚀。

  • 2.3 锈层电化学分析

  • 对 72、168 及 504 h 三个周期试验后试样锈层的极化曲线和交流阻抗谱进行测定。图15 为不同 Cl 浓度周浸后试样的动电位极化曲线及 Tafel 拟合结果,所有曲线的形状基本一致,这说明碳钢在这些环境中的腐蚀机理是一致的。通过 Tafel 拟合得到腐蚀电流 Icorr,结果表明,所有试验周期的试样随着 Cl 浓度的升高,腐蚀电流都相对应增大。这说明溶液中 Cl 浓度增大导致锈层的保护性下降,这与上述腐蚀大数据分析结果一致。所有试验环境中,随着试验周期的延长,腐蚀电流逐渐减小,与失重结果一致。

  • 图15 不同 Cl 浓度溶液周浸后碳钢的动电位极化曲线及 Tafel 拟合结果

  • Fig.15 Dynamic potential polarization curves and Tafel fitting results of carbon steel after periodic immersion in different Cl⁻ concentration solutions

  • 图16 为不同 HSO3 浓度溶液中周浸后试样的动电位极化曲线及 Tafel 拟合结果。从腐蚀电流中可以看出,72、168 及 504 h 三个周期试验后试样的腐蚀电流都随着 HSO3 浓度的增加而增大,这说明 HSO3 浓度越高,腐蚀速率越快,HSO3 会促进腐蚀的进行。并且随着试验周期的增加,由 HSO3 浓度增加导致的腐蚀加速更加明显[16],504 h 后,0.1% 和 0.2% HSO3 环境下周浸试样的腐蚀速率远大于 0.05% HSO3

  • 图17 为不同 pH 值溶液周浸后,碳钢的动电位极化曲线及 Tafel 拟合结果。pH 值对碳钢腐蚀的影响规律十分明显。随着 pH 值的降低,腐蚀电流增大,说明 pH 值的降低加快了碳钢的腐蚀速率,随试验的进行,仍然延续这一规律。

  • 图16 不同 HSO3 浓度溶液周浸后碳钢的动电位极化曲线及 Tafel 拟合结果

  • Fig.16 Dynamic potential polarization curves and Tafel fitting results of carbon steel after periodic immersion in different HSO3⁻ concentration solutions

  • 图17 不同 pH 值溶液周浸后碳钢的动电位极化曲线及 Tafel 拟合结果

  • Fig.17 Dynamic potential polarization curves and Tafel fitting results of carbon steel after periodic immersion in different pH solutions

  • 2.4 锈层截面分析

  • 周浸试验完成后,对试验周期为 504 h 的碳钢锈层截面进行形貌观察,使用 EDS 对元素分布进行分析,如图18~20 所示。504 h 周浸后所有试样都出现了锈层脱落的情况,图18 为不同 Cl 浓度环境下,碳钢锈层截面形貌及元素分布图。从图中可以看出,随着 Cl 浓度的增加,锈层的厚度不断增加。并且在周浸环境 Cl 浓度较低时,锈层外侧有较明显的 Cl 元素聚集,说明此时的锈层具有一定的保护性,可以阻止 Cl 元素进入锈层内部。然而 Cl 浓度较高时,Cl 元素无明显聚集或者少量进入锈层内部。

  • 图18 不同 Cl 浓度溶液周浸加速试验后碳钢锈层截面形貌及元素分布

  • Fig.18 Cross-sectional morphology and elemental distribution of the rust layer on carbon steel after accelerated periodic immersion experiment in different Cl⁻ concentration solutions

  • 图19 不同 HSO3 浓度溶液周浸加速试验后碳钢锈层截面形貌及元素分布

  • Fig.19 Cross-sectional morphology and elemental distribution of the rust layer on carbon steel after accelerated periodic immersion experiment in different HSO3⁻ concentration solutions

  • 图19 为不同 HSO3 浓度环境下周浸后试样的锈层截面形貌及元素分布图。可以看出,随 HSO3 浓度的增加,锈层的厚度同样不断增加,但锈层裂纹数量明显增多,说明锈层的稳定性降低。HSO3 浓度较低时,仍能在锈层外侧观察到少量 Cl 元素聚集,说明此时锈层具有一定的保护性,阻碍 Cl 元素进入锈层内部。

  • 图20 为不同 pH 值环境下周浸后试样的锈层截面形貌及元素分布图。可以看出,随着 pH 值降低,锈层裂纹数量明显增多,导致锈层保护性下降,从 Cl 元素在锈层外侧的分布情况可以验证这一结论。在 pH=5 的溶液中周浸后的试样,Cl 元素均匀分布在碳钢的锈层外侧,说明此时的锈层仍具一定的保护性。当 pH=3 时,Cl 元素开始进入锈层内部以及基体表面。

  • 图20 不同 pH 值溶液周浸加速试验后碳钢锈层截面形貌及元素分布

  • Fig.20 Cross-sectional morphology and elemental distribution of the rust layer on carbon steel after accelerated periodic immersion experiment in different pH solutions

  • 2.5 腐蚀形貌分析

  • 蚀坑深度是碳钢耐蚀性能的重要评估指标[20],因此,利用激光共聚焦技术,对周浸 504 h 后去除表面锈层后的碳钢进行 3D 微观腐蚀形貌分析,如图21~23 所示。可以看出,随周浸环境中 Cl 浓度的升高,碳钢的蚀坑数量有所增加。浓度较低时,蚀坑深度相对较浅,随浓度增加,蚀坑不仅增多增深,而且不断扩展汇聚。随着环境中 HSO3 浓度上升,蚀坑深度不断增加,并且呈扩展汇聚的趋势。图23 为不同 pH 值环境下周浸的结果,pH 值降低同样导致碳钢腐蚀的蚀坑深度增加,并且蚀坑的特点从小而浅逐步转化为大且深。

  • 图21 不同 Cl 浓度溶液周浸加速试验后腐蚀形貌分析

  • Fig.21 Corrosion morphology analysis after accelerated periodic immersion experiment in different Cl⁻ concentration solutions

  • 图22 不同 HSO3 浓度溶液周浸加速试验后腐蚀形貌分析

  • Fig.22 Corrosion morphology analysis after accelerated periodic immersion experiment in different HSO3⁻ concentration solutions

  • 图23 不同 pH 值溶液周浸加速试验后腐蚀形貌分析

  • Fig.23 Corrosion morphology analysis after accelerated periodic immersion experiment in different pH solutions

  • 3 结论

  • 结合腐蚀大数据传感器,通过在多种模拟海洋大气溶液中进行周期浸泡加速试验,并对试样的失重、锈层电化学、锈层形貌及腐蚀形貌进行分析表征,研究不同海洋大气环境下碳钢腐蚀行为的影响,可以得出以下结论:

  • (1)随着 Cl 浓度的增加,腐蚀累积总量呈不断上升的趋势。当 Cl 浓度较低时,锈层朝着更加稳定的方向发展,锈层对基体的保护性有所增加,腐蚀相对电流强度不断下降,腐蚀速率减小。

  • (2)随着 HSO3 浓度的增加,腐蚀累积总量也呈不断上升的趋势。0.05% HSO3 浓度下,腐蚀从始至终以相对较低的速率匀速进行;浓度为 0.1%时,腐蚀先是匀速进行,在腐蚀后期,由于形成了具有一定保护性的锈层,腐蚀速率下降。

  • (3)从腐蚀累积量来看,pH 值的降低导致腐蚀总量增加。pH=5 和 3 时,整个试验周期内,腐蚀速率呈下降趋势。

  • (4)对比腐蚀大数据方法与传统挂片法研究结果,两种方法具有较高的一致性,验证了腐蚀大数据手段对于环境腐蚀研究的可靠性,为后续开展数据分析及挖掘奠定基础。

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