直流干扰下新型镁铝合金牺牲阳极的腐蚀特性研究

Study on Corrosion Characteristics of New Mg-Al Alloy Sacrificial Anode under DC Interference

考虑到西南山区管道所处环境具有土壤电阻率大、受直流杂散电流干扰的特点,设计了一种新型镁铝合金牺牲阳极,其中铝含量达到了5%。牺牲阳极的电流效率易受Cl^(-)浓度的影响。为了表征牺牲阳极在复杂土壤环境中的适用性,通过室内电化学测试方法分析了不同直流电位和氯离子浓度下新型镁铝合金牺牲阳极的腐蚀特征。结果表明:随着直流电位的增加(0~5 V),牺牲阳极开路电位的正向偏移程度增大,表明直流电位促进了牺牲阳极的腐蚀反应速率,缩短了其使用寿命;但是相对于1 V和5 V的直流电位来说,在3 V直流电位条件下牺牲阳极的腐蚀速率相对较小,这与该条件下牺牲阳极表面被形成的腐蚀产物覆盖有关。随着Cl^(-)浓度增大(0~0.5 mol/L),牺牲阳极开路电位偏移程度明显增大,并且Cl^(-)浓度越高,对牺牲阳极工作性能影响越大。与传统镁阳极的电流效率相比,在直流干扰下,且高含氯环境中,新型镁铝阳极的电流效率提升了40%,这是因为新型镁铝阳极形成的镁-铝原电池极大地促进了阳极的反应过程.

Considering that the pipelines in the southwest mountainous area are faced with an enviornment having the characteristics of large soil resistivity and DC stray current interference,a new type of magnesium aluminum alloy sacrificial anode,in which the aluminum content was up to 5%,was designed.As the sacrificial anode current efficiency was susceptible to Cl^(-)concentration,in order to characterize the applicability of the sacrificial anode in complex soil environments,the corrosion characteristics of the new magnesium aluminum alloy sacrificial anode under different DC potentials and chloride ion concentrations were analyzed by an indoor electrochemical test method.Results showed that with the increase of DC potenital(0~5 V),the positive deviation of the open circuit potential of sacrificial anode increased,indicating that the DC potential promoted the corrosion reaction rate of sacrificial anode and reduced its service life.However,compared with the corrosion rates in the cases of 1 V and 5 V DC potential,the corrosion rate was smaller under the condition of 3 V DC potential.This was attributed to the coverage of sacrificial anode by the corrosion product formed on its surface.With the increase of Cl^(-)concentration(0~0.5 mol/L),the offset degree of open-circuit potential of sacrificial anode increased obviously,and the influence of the Cl^(-)on the performance of sacrificial anode grew with the increase of its concentration.Compared with the current efficiency of the traditional magnesium anode,the current efficiency of the new Mg-Al anode was increased by 40%in high chlorine-containing environment with a DC interference,as the Mg-Al galvanic cell formed in the anode greatly promoted the anode reaction process.