X70钢在含氯化钠粉土中的电化学腐蚀行为研究

Study on Electrochemical Corrosion Behavior of X70 Steel in Silt Containing Sodium Chloride

针对盐渍土对埋地金属管线腐蚀性问题,本文利用电化学阻抗技术和极化曲线技术,研究了X70钢在不同含水量和含氯化钠粉土中的电化学腐蚀行为。结果表明:X70钢在含氯化钠粉土中的Nyquist图均由双圆弧组成;同一含盐量下,X70钢的腐蚀速率随着含水量的增加先增大后减小,在含水量为22%时,腐蚀速率最大;同一含水量下,X70钢的腐蚀速率随着含盐量的增加先增大后减小,在含盐量为2%时,腐蚀速率最大。一方面,过高的含水量使得土壤胶粒膨胀,氧气传输路径受阻,另一方面,随着含盐量增加,氧溶解度降低,使得结合层电阻R;与电荷转移电阻R;呈现出先减小后增大的现象,相应的腐蚀速率先增大后减小。由Bode图中的阻抗模值随着含盐量和含水量的增加先变小后变大进一步验证了这一规律。

Aiming at the corrosivity of saline soil to buried metal pipelines, this paper uses electrochemical impedance technology and polarization curve technology to study the electrochemical corrosion behavior of X70 steel in silt with different water content and salt content.The results show that the Nyquist diagrams of X70 steel in sodium chloride silt are composed of double arcs;under the same salt content, the corrosion rate of X70 steel first increases and then decreases with the increase of water content. When the water content is 22%, the corrosion rate is the highest.. Under the same water content, the corrosion rate of X70 steel first increases and then decreases with the increase of the salt content. When the salt content is 2%, the corrosion rate is the largest;The high water content makes the soil colloidal particles swell and the oxygen transmission path is blocked. On the other hand, as the salt content increases, the oxygen solubility decreases, making the bonding layer resistance R;and the charge transfer resistance R;show a phenomenon of first decreasing and then increasing. The corresponding corrosion rate first increases and then decreases. The impedance modulus in the Bode diagram first becomes smaller and then becomes larger with the increase of salt content and water content. This rule can also be explained.