Holographic interferometry, an electromagnetic method, was used to study corrosion of carbon steel, aluminum and copper nickel alloys in NaOH, KC1 and H2SO4 respectively. The technique, called electrochemical emission spectroscopy, consisted of in-situ monitoring of changes in the number of fringe evolutions during the corrosion process. It allowed a detailed picture of anodic dissolution rate changes of alloys. The results were compared to common corrosion measurement methods such as linear polarization resistance and electrochemical impedance spectroscopy. A good agreement between both data was found thus indicating that holographic interferometry can be a very powerful technique for in-situ corrosion monitoring.
In recent works conducted by the author [1-16], all optical transducer was developed for materials testing and evaluation of different electrochemical phenomena. The optical transducer was developed based on incorporating methods of holographic mterferometry for measuring microscopic deformations and electrochemical techniques for determining electrochemical parameters of samples in aqueous solutions. In addition to the optical transducer being as an electrometer for measuring different electrochemical parameters but also, it was used as a 3D-interferometric microscope for detecting different micro-alterations at a metal surface in aqueous solution, at a microscopic scale. In previous studies, the optical transducer was applied successfully in determining the mechano-chemical properties in aqueous solutions by detecting micro-deformations and measuring the corresponding current density by the optical transducer fl-5] It was also used as an optical corrosion-meter [6-8] by measuring:
? cathodic deposition and anodic dissolution layers of metals in aqueous solutions.
? cathodic and anodic current densities which correspond to the cathodic deposition and anodic
dissolution layers, respectively.
? uniform corrosion and localized corrosion on metal surfaces and on substrates covered by organic coatings or under crevice assemblies [8-14].
It was also used to document adsorption and desorption phenomena of chemical species on metal surfaces in aqueous solutions [12]. Finally, the optical transducer was applied as an electrometer for measuring the double layer capacitance, the alternating current impedance and the corresponding oxide layer thickness of metals in aqueous solution [~5-16~.
The objective of the present work was to determine the rate change of the number of the fringe
evolutions during the corrosion test of carbon steel, aluminum and copper nickel alloys in NaOH, KC1 and H2SO4 respectively. The technique, called electrochemical emission spectroscopy, consisted of in- situ monitoring of changes in the number of fringe evolutions during the corrosion process. It allowed a detailed picture of anodic dissolution rate changes of alloys. The results were compared to common corrosion measurement methods such as linear polarization resistance and electrochemical impedance spectroscopy [171. A good agreement between both data was found thus indicating that holographic interferometry can be a very powerful technique for in-situ corrosion.
THEORETICAL ANALYSIS
In a mathematical relationship derived by the author elsewhere [7-s], one can measure the corrosion current density (J) of metallic samples in aqueous solutions according to the following mathematical model [7~sl:
Equation (1)
Where J is the corrosion current density of the based metal
Holographic Imerferometry, Electrochemical Impedance (E.I) spectroscopy,
Electrochemical-Emission Spectroscopy, linear Polarization, Corrosion, and He Ne L
