Impressed current technique is a widely adopted method for accelerating corrosion of steel reinforcement. The mass loss of steel can be theoretically estimated by Faraday's law with the assumption that all of the impressed current participated in the corrosion reaction. In the present study, accelerated corrosion process of reinforcing steel with impressed current was non-destructively traced by X-ray micro-computed tomography (μCT) with high accuracy. The mass loss of steel at different accelerated corrosion periods was analyzed and the efficiency of impressed current was calculated. It was found that the mass loss of steel did not always follow Faraday's law, and impressed current efficiencies varied with different corrosion periods. In the early corrosion periods, the water electrolysis occurred and lowered the current efficiency due to the high anode potential. While in the late corrosion periods, the natural corrosion caused the current efficiency to exceed 100%.

外加电流技术是加速钢筋腐蚀的一种广泛采用的方法。可以通过法拉第定律在理论上估计钢的质量损失，并假设所有施加电流都参与了腐蚀反应。在本研究中，通过X射线微计算机断层扫描（μCT）可以高精度地无损地追踪施加强电流对钢筋的加速腐蚀过程。分析了不同加速腐蚀时间段钢的质量损失，并计算了施加电流的效率。结果发现，钢的质量损失并不总是遵循法拉第定律，而且不同的腐蚀时间所产生的电流效率也不同。在腐蚀初期，由于阳极电位高，发生了水电解并降低了电流效率。在腐蚀后期，自然腐蚀导致电流效率超过100％。