doi: 10.11902/1005.4537.2016.151
L245钢在不同温度下的油气田模拟水中的腐蚀行为研究

Corrosion Behavior of L245 Steel in Simulated Oilfield Produced Water at Different Temperatures

Abstract:

The corrosion behavior of L245 steel in simulated oilfield produced water was investigated by means of weight loss measurement, polarization curve measurement, electrochemical impedance spectra (EIS) and SEM. The results showed that the corrosion reaction of L245 steel is more intensive at higher temperature. When the temperature of the solution is elevated from 30 ℃ to 90 ℃, the corrosion current density of L245 steel in the solution with saturated CO2 increases from 66.1 μAcm-2 to 177 μAcm-2 while the charge transfer resistance of L245 steel decreased from 5155 Ωcm2 to 1182 Ωcm2. The above results indicated that the corrosivity of oilfield produced water increased with the increasing temperature within the range of 30~90 ℃, localized corrosion of the steel occurred at 60 ℃, then the localized corrosion would be intensified when the temperature is elevated to 90 ℃.

Key words: L245 steel ; simulated oilfield water ; temperature ; corrosion rate

1 实验方法
1.1 实验材料的制备

1.2 浸泡实验失重处理

1.3 电化学测量

1.4 腐蚀形貌分析

2 结果与讨论
2.1 失重实验

Fig.1 Corrosion rates of L245 steel after immersed in simulated oilfield produced water with different temperatures for 10 d

2.2 电化学测试

2.2.1 动电位极化曲线测试结果 图2为L245钢在不同温度下的动电位极化曲线,表1是各极化曲线的电化学参数拟合结果。从图2中可以看出,当温度升高时,L245钢的自腐蚀电位正移,整体处于活化溶解状态。从表2可以看出,随着温度升高L245钢的腐蚀电流逐步增大,腐蚀速率不断加快。当温度升高至90 ℃时自腐蚀电流升高到177 μAcm-2,远远大于其余两个温度条件下的自腐蚀电流,说明L245钢在高温下反应比较剧烈。同时通过表2可以看出,随着温度的升高ba的变化不大,而bc的变化较大,说明温度升高对阳极反应影响较小,而对阴极反应影响较大,从而可知腐蚀反应过程主要由阴极控制。

2.2.2 电化学阻抗测量结果 图3为L245钢在不同温度下的Nyquist图和Bode图。可以看出随着温度的升高,L245钢的容抗弧不断减小,从Bode图中可以看出,温度升高相位角峰向高频移动,说明L245钢的抗腐蚀性随着温度升高逐渐减弱,说明温度的升高减小了腐蚀反应的阻力,导致腐蚀速率增加,这一结果与极化曲线的结果一致。

Fig.2 Polarization curves of L245 steel in oilfield produced water with different temperatures

Fig.3 Nyquist (a) and Bode (b) diagrams of L245 steel in simulated oilfield produced water with different temperatures

Fig.4 Electrochemical equivalent circuits used for modeling of EIS of L245 steel in simulated oilfield produced water with different temperatures

Table 1 Polarization curves fitting results of L245 carbon steel at different temperatures in simulated oilfield produced water

Table 2 Electrochemical parameters fitted from the EIS at different temperature

2.3 腐蚀表面形貌结果

Fig.5 SEM images of L245 steel after immersion in simulated oilfield produced water for 10 d at 30 ℃ (a),60 ℃ (b) and 90 ℃ (c)

2.4 分析与讨论

$Fe → F e 2 + + 2 e -$ (1)

$C O 2 + H 2 O → H 2 C O 3$ (2)

$H 2 C O 3 → HC O 3 - + H +$ (3)

$HC O 3 - → C O 3 2 - + H +$ (4)

$2 H 3 O + + 2 e - → 2 H 2 O + H 2$ (5)

$C O 2 + H 2 O + Fe → FeC O 3 + H 2$ (6)

3 结论

(1) 温度对L245钢的CO2腐蚀有显著影响,在低温阶段 (≤90 ℃),腐蚀速率随着温度的升高而加快。

(2) 常温下 (30 ℃) L245钢的CO2腐蚀主要为均匀腐蚀,当温度升高至60 ℃开始发生局部腐蚀,局部腐蚀反应随着温度升高而加剧。

The authors have declared that no competing interests exist.

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L245钢

L245 steel
simulated oilfield water
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ZHU Ming
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ZHANG Huihui