Abstract: Brass tube in simulated circlating cooling system was studied by means of electrochemical impedance spectrum(EIS) and electrochemical noise(EN).EIS shows that the inhibitor can react with metal surface or corrosive product and inhibit the corrosion process by forming protective film.With the flow rate increasing, the diffuse speed of oxygen increases and the process of film forming accelerates in HAl77-2 tube，resulting in a decreasing corrosion speed.EN shows that the flow rate has little effect on the susceptibility of pitting corrosion of HSn70-1 tube.But the susceptibility of pitting corrosion of HAl77-2 tube increases with an increasing flow rate.The result is in full agreement with actual conditions.It shows that the electrochemical noise technique is good for corrosion monitoring.The flow rate has a significant effect on the sensor placed countercurrently and has little effect on the sensor placed concurrently.So the sensor should be placed concurrently in application to decrease the effect of flow rate.The result of experiment shows that the sensor can successfully monitor the corrosion in flowing seawater.