Optical interferometry as electrochemical emission spectroscopy of copper alloys in seawater

Abstract

In the present investigation, holographic interferometry was utilized for the fast time to determine the rate change of the number of the fringe evolutions during the corrosion test of a pure copper, 99% Cu, and an aluminium brass, 76% Cu +22% Ni +2%Al, in natural seawater. In other words, the anodic dissolution behaviours (corrosion) of the pure copper and the aluminium brass were determined by holographic interferometry, an electromagnetic method. Thus, the abrupt rate change of the number of the fringe evolutions during corrosion tests of both the copper alloys is called electrochemical emission spectroscopy. The corrosion process of both copper alloys was carried out in the seawater at room temperature. The electrochemical emission spectra of both copper alloys in seawater represent a detailed picture of the rate change of the anodic dissolution of both copper alloys throughout the corrosion processes. Furthermore, the optical interferometry data of the both copper alloys were compared to data obtained from the common methods of electrochemical techniques of corrosion measurements, namely, the linear polarization method and electrochemical impedance spectroscopy. The comparison indicates that there is good agreement between the data ofthe electrochemical emission spectra of both copper alloys with data of the electrochemical techniques in seawater. In both techniques of electrochemical emission spectroscopy and electrochemical techniques, the corrosion behaviour of the pure copper was observed to be higher than that of aluminium brass. Consequently, holographic interferometry was found very useful for monitoring the anodic dissolution behaviours ofmetals, in which the number ofthe fringe evolutions ofboth copper alloys can be determined in situ.