Electrochemical Noise Analysis of 20# Steel with Different pH Value in Sodium Chloride Solution

The corrosion behavior of 20# steel in sodium chloride solution with deferent pH value has been studied by the electrochemical noise (EN) technique. The EN data was analyzed using methods of the frequency-domain, time-domain and wavelet analysis. The result show that the Cl- in the solution for high pH value effect local corrosion process at the matrix that caused the difference spectrum of electrochemical noise analysis. With the high pH value condition, localized corrosion was occurred for Cl- in the early stage of the experiment mainly. For the pH value decreased, uniform corrosion of H+ was in a dominant position on the substrate, When pH reached 3, due to H+ concentration is larger, greatly promoted the activity of Cl-, therefore, there was some localized corrosion happened in the middle of the experiment. The wavelet analysis show that different bands correspond to different corrosion behavior and the result is consistent with the conclusion of others analysis method.