Purpose

The paper aims to study the effect of liquid flow velocity on corrosion behavior of 20# steel at initial stage under (CO2/aqueous solution) gas–liquid two-phase plug flow conditions.

Design/methodology/approach

Weight loss, scanning electron microscopy, energy-dispersive X-ray spectroscopy and XPS methods were used in this study.

Findings

The corrosion rate increased with the increasing liquid flow velocity at any different corrosion time. The corrosion rate decreased with the extension of corrosion time at the same liquid flow velocity. There was no continuous corrosion products film on the whole pipe wall at any different corrosion time. The macroscopic brown-yellow corrosion products on the pipe wall surface decreased with the increasing liquid flow velocity and the loose floccus corrosion products decreased gradually until these products were transformed into un-continuous needle-like dense products with the increasing liquid velocity. The main elements among the products film were Fe, C and O, and the main phases of products film on the pipe wall were Fe3C, FeCO3, FeOOH and Fe3O4. When the corrosion time was 1 h under different liquid–velocity condition, the thickness of local corrosion products film was from 3.5 to 3.8 µm.

Originality/value

The ion mass transfer model of corrosion process in pipe was put forward under gas–liquid two-phase plug flow condition. The total thickness of diffusion sublayer and turbulence sublayer decreased as well as the turbulence propagation coefficient increased with the increasing liquid velocity, which led to the increasing velocity of ion transfer during corrosion process. This was the fundamental reason for the increase of corrosion rate with the increasing liquid velocity.

中文翻译：

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气液两相塞流条件下液体流速对20＃钢初期腐蚀行为的影响

目的

本文旨在研究在（CO2 /水溶液）气液两相塞流条件下，液体流速对20＃钢初始腐蚀行为的影响。

设计/方法/方法

在这项研究中使用了重量损失，扫描电子显微镜，能量色散X射线光谱法和XPS方法。

发现

在任何不同的腐蚀时间，腐蚀速率都随着液体流速的增加而增加。在相同的液体流速下，腐蚀速率随腐蚀时间的延长而降低。在任何不同的腐蚀时间下，整个管壁上都没有连续的腐蚀产物膜。随着液体流速的增加，管壁表面宏观的棕黄色腐蚀产物逐渐减少，疏松的絮状腐蚀产物逐渐减少，直到随着液体流速的增加，这些产物转变为不连续的针状致密产物。产品膜中的主要元素为Fe，C和O，管壁上产品膜的主要相为Fe3C，FeCO3，FeOOH和Fe3O4。当在不同的流速条件下腐蚀时间为1 h时，

创意/价值

提出了气液两相塞流条件下管道腐蚀过程的离子传质模型。随着液速的增加，扩散子层和湍流子层的总厚度减小，湍流传播系数增加，从而导致腐蚀过程中离子转移速度的增加。这是随着液体速度增加腐蚀速率增加的根本原因。