Abstract: Describes the influence of the concrete JR drop on the results of electrochemical measurements carried out on reinforcing steel corrosion in concrete and the resulted errors in judgement or evaluation of rebar corrosion. Through a new electrochemical measuring method i.e transient switch method conducted on reinforcing steel corrosion in concrete, not only the influence of JR drop but also the influence of concentration polarization in rebar surface can be effectively eliminated. Thus polarization curves can be obtained under the influence of electrochemical polarization only. Kinetics parameters of the electrochemical processes can be calculated referring to stationary methods using the data obtained.