Work Item
ASTM WK85527

## New Guide for Determination of Corrosion Rate with Electrochemical Harmonic Measurement and Analysis

###### 1. Scope

1.1 This guide covers an experimental procedure for running electrochemical harmonic measurement in the laboratory and determination of the harmonic current and corrosion rate using harmonic analysis (HA). Corrosion current is calculated by applying HA, which can be used to measure and monitor the corrosion rate of metals in corrosive environments.
1.2 This guide covers mathematical derivation and analysis of the corrosion rate of metals using electrochemical HA based on the Butler-Volmer equation for corrosion reactions. The technique is suited mainly for corrosion processes that are rate-limited by charge transfer reactions, diffusion, and passivating processes.
1.3 This guide covers specimen preparation, test environment, experimental procedure, computation using the measured data, and results analysis to obtain the corrosion rate of the sample of interest.

###### Keywords

linear polarization resistance, electrochemical impedance spectroscopy, and electrochemical noise

###### Rationale

Determination of corrosion rate is important for corrosion science and engineering. Many standards utilize techniques such as linear polarization resistance, electrochemical impedance spectroscopy, and electrochemical noise which are well-developed and acknowledged in research. All these standards are based on linear electrochemical techniques. With regards to non linear electrochemical phenomena and other methods to characterize the corrosion rate, potential perturbation signals with one or more sine waves at different frequencies have been applied. In the current guide, electrochemical harmonic measurement and its analysis are presented. A single frequency sine wave perturbation with defined amplitude is applied to a metal sample at open circuit potential. The resulting current response is recorded over time and then transformed to the frequency domain by Fast Fourier transform (FFT). The amplitudes of the first, second, and third harmonics of current are then obtained to compute the corrosion current and corrosion rate as well as the Tafel Slopes based on non linear electrochemical theory.

The title and scope are in draft form and are under development within this ASTM Committee.

###### Details

Developed by Subcommittee: G01.11

Committee: G01

Staff Manager: Krista Robbins

###### Work Item Status

Date Initiated: 03-06-2023

Technical Contact: John Zhang

Item: 000

Ballot:

Status: