09575 The Effect of Electrode Size on Electrochemical Noise Measurements and the Role of Cl- on Localized Corrosion for Mild Steel in CO2 Corrosion Environment

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Product Number: 51300-09575-SG

ISBN: 09575 2009 CP

Author: Xiu Jiang, Franaois Huet and Srdjan Nesic

Publication Date: 2009

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The simultaneous fluctuations of potential noise and current noise between two nominally identical X- 65 mild steel electrodes were recorded in deaerated aqueous sodium chloride solutions with concentration ranging between 1 and 20 wt % at 80oC. Electrochemical noise (EN) was obtained from both 11.6 cm2 and 1 cm2 coupons in 1 wt % NaCl solution to learn how the surface area affects EN measurements. Only small surface area coupons (1 cm2) were used in 10 wt % and 20 wt % NaCl solution experiments to understand the role of Cl- on localized corrosion processes. Linear polarization resistance measurements were conducted in each experiment to investigate the general corrosion behavior. The surface morphology of coupons was observed with a scanning electrochemical microscope (SEM). The results showed that the electrode area influenced the EN signal. Transients related to metastable pitting were best observed with 1 cm2 coupons in 1, 10, and 20 wt % NaCl solutions, but such transients were not clearly obtained for 11.6 cm2 coupons in the 1 wt % NaCl solution. Both statistical analysis of recorded current and potential noise and SEM analysis showed that increasing the NaCl solution concentration did not change the localized corrosion rate.

Keywords: Localized CO2 corrosion, mild steel, electrochemical noise, electrode size, NaCl concentration