亚硝酸根浓差作用下混凝土中钢筋的腐蚀特征

Corrosion characterization of the steel bar in reinforced concrete under differential nitrite ion concentration

通过含氯盐与亚硝酸盐钢筋混凝土加速腐蚀试验,结合腐蚀面积率和失重率综合评价亚硝酸盐掺量均匀以及两侧存在浓差时钢筋的腐蚀情况.结果表明:亚硝酸盐掺量均匀时,随着NO_2^-浓度增加阻锈效果增强,且n[2NO-]/n[Cl^-]比值达到1.2时完全阻锈;亚硝酸盐存在浓度差时,即使n[2NO-]/n[Cl^-]为1.5也不能完全阻锈;大阳极NO_2^-浓度变化不会影响阻锈性能,但小阳极上NO_2^-浓度变化引起的浓差对阻锈性能有影响,甚至加速腐蚀;钢筋两侧NO_2^-浓度差保持不变时,改变阴、阳两极面积比对钢筋的腐蚀影响较小;高浓度的NO_2^-作用时,钢筋两侧的NO_2^-浓度差增大,导致钢筋加速腐蚀.

In accelerated steel corrosion experiment of reinforced concrete containing various quantities of calcium chloride and calcium nitrite, the corrosion characterization of steel under uniform and differential nitrite ion concentration was determined by mass loss degree and corrosion area ratio. The results showed that the effect of corrosion prevention enhanced with the increase of nitrite, and the corrosion was inhibited nearly completely at a molar ratio of 1.2 or more in the concrete with uniform molar ratios. However, the corrosion was not inhibited completely at a molar ratio of 1.5 when the nitrite was different. Unlike the anode, however, the content changes of nitrite in cathode sometimes even weaken the anti-corrosion effect of steel. Moreover, the cathode and anode area ratio did not cause much difference about anti-corrosion effect by keeping the nitrite constant. While under high concentration of nitrite, the bipolar nitrite concentration difference turned out to be speeding up the corrosion of the steel.