ABSTRACT

It is well known that electronic instrumentations, i.e. Ammeter, Potential-meter, have been used for years to measure electrochemical properties of metallic electrodes in aqueous solutions. One of the disadvantages of using electronic instruments for the measurement of electrochemical properties is the invasive nature of those instruments to the electrochemical systems of the metallic electrodes in aqueous solutions. In recent work published elsewhere TM, it has been shown that laser optical interferometry can be used as an optical transducer to characterize the electromagnetic field which develops as a result of the electron conduction in metallic electrodes in aqueous solutions due to the anodic reaction, corrosion processes, between the electrodes and the aqueous solutions, The characterization of such electromagnetic field and a mathematical correlation of the electromagnetic field to any electrochemical properties, i.e., corrosion current density, double layer capacitance, alternating current impedance, and so on, would lead to the measurement of the electrochemical properties by optical interferometry, by the non-invasive method.

In the present work, the corrosion current density of a low carbon steel, a pure aluminum, a stainless steel, a Copper-Nickel alloy were obtained in 1M NaOH, 1M KC1, 1M NaC1, 1M H2SO4 solutions, respectively. The obtained corrosion data from the optical interferometry technique, as a zero resistance Ammeter were compared with corrosion data obtained on the same alloys in the specified solutions from an electronic zero resistance-Ammeter as well as from the linear polarization method. The comparison among the three techniques indicates that there is a contrast in the results among the investigated alloys. In general, the results of the optical interferometry were found in agreement with the electronic zero resistance-Ammeter as compared with the linear polarization method. As a result, the optical interferometry can be considered as a useful zero resistance-Ammeter for measuring the corrosion current density of metallic electrodes in aqueous solutions at the open circuit potential of the electrodes in the aqueous solutions.

INTRODUCTION

In recent work published elsewhere 116, a novel technique for monitoring the mechanochemical behaviours, i.e., stress corrosion cracking, corrosion fatigue, and hydrogen embrittlement, of metallic electrodes in aqueous solutions has been developed. The technique incorporates holographic interferometry for measuring microscopic deformation and electrochemical techniques for determining the corrosion current of metallic samples, As a result, the techniques of holographic interferometry have many potential applications in the field of electrochemistry yet to be explored.

In addition, mathematical models describing the cathodic deposit and anodic dissolution of 6-8 metals by holographic interferometry were derived . Furthermore, Holographic interferometry was utilized to develop an optical corrosion-meter, in which corrosion of metallic alloys can be measured in 8 aqueous solutions without any physical contact.

The objective of the present work was to measure the corrosion current density of a low carbon steel (UNS No.1020, 0.2%C, 0.45%Mn, 0.25%Si, and balanced Fe), a pure aluminium (99.7%A1), a stainless steel (UNS No.304 stainless steel, 19%Cr, 9%Ni, 0.45%Mn, and balanced ofFe),and a Copper- Nickel alloy ( 70%Cu and 30%NI) in 1M NaOH, 1M KC1, 1M NaC1, 1M H2SO4 solutions, respectively by the holographic interferometry technique. Furthermore, the work aimed to compare the obtained data of the corrosion current density of the optical interfermetry with other techniques of the corrosion 17-18 measurement

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