ABSTRACT

It is important to monitor the corrosion rates of steel in electrolyte environments such as aqueous solution or soil in order to evaluate the integrity of the members of facilities. As the nondestructive monitoring method, polarization resistance (Rp) method is generally known. The corrosion rate icor is calculated by the equation of icor=k/Rp. Herein k is a constant decided on the specific condition of steel surface and the environment. It is not easy to decide k on each condition. As a monitoring method without deciding k has been demanded, CIPE (Current Interrupted Polarizing Extrapolation) method was developed. By CIPE method the corrosion rate is calculated by the Tafel equation obtained from the polarization curve of in situ measurement. In this paper, in order to confirm accuracy of the method, the measured corrosion rates of carbon steel were compared with the values calculated from mass losses of steel specimens in neutral aqueous solution. As a result, the mass losses calculated form corrosion rates by CIPE method indicated the similar values of the actual corrosion mass losses. Therefore it is clear that CIPE is a useful method for real time monitoring of corrosion rate of steel in aqueous solution.

INTRODUCTION

It is important to monitor the corrosion rates of steel in electrolyte environments such as aqueous solution or soil in order to evaluate the integrity of the members of facilities. As the nondestructive monitoring method, polarization resistance (Rp) method is generally known. The corrosion rate icor is calculated by the equation of icor=k/Rp. Herein k is a constant decided on the specific condition of steel surface and the environment. It is not easy to decide k on each condition. As a monitoring method without deciding k has been demanded, CIPE (Current Interrupted Polarizing Extrapolation) method was developed. 1 This method is called CIPE for the abbreviation of the name in this paper. By CIPE method the corrosion rate is calculated by the Tafel equation obtained from the polarization curve of in situ measurement.

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