Wavelet Transform-Based Analysis For Electrochemical Noise Of Metal Corrosion

It's urgently required to loose the destruction and loss caused by corrosion to a minimum either from the economic or social considerations, which can make the equipment and metal device work for long securely. It's important to improve the technology of material choice and antisepsis design, however, developing the method to measure corrosion plays a practical role in understanding the status, speed and rule of corrosion. The development of electrochemical noise technology is closely relative to the development of electronics, computer and mathematics technology.Electrochemical noise technology induces constant electric quantity, generates disturbance in the corrosive system in a very short time using the electric charge with known quantity as the stimulant signal, records the relation curve between polarized electric potential and time, and gets the electrochemical parameters after the analysis and process.The signals obtained by computer are affected by noise drastically since the electrode response signal induced by the coulostatic perturbations is faint. The noise degrades the accuracy and precision of the analysis and detection. Signal denoising is therefore highly desirable.Wavelet transform is a time-scale (time-frequency) method, it is a multi-resolution analysis method, and it has good ability to express both time and frequeny domain character.In this paper, based on time-frequency multi-resolution analysis theory, wavelet method is respectively proposed to separate noise from coulostatically induced transients. A method of denoising based on wavelet thresholding for coulostatically induced transients is presented. In this method, noisy data could be extracted by reducing the wavelet coefficients under a quantity equal to the threshold value. Some key factors such as thresholding policy are further discussed.Secondly, use EDP method to analyse stress corrosion cracking noise. EDP is useful in identifying the complex signal. According to the signal energy distribution plot, the signal which corresponded to different type corrosion can be extracted from the records based on wavelet transform, and then the extent of the corrosion can be calculated.