In a previous study , a mathematical model relating surface and bulk behaviors of metals in aqueous solution has been developed. The model was established based on principles of holographic interferometry for measuring microsurface dissolution, i.e. mass loss , and on those of electrochemistry for measuring the bulk electronic current, i.e. corrosion current. In the present wok , an optical corrosion-meter was built based on the above model. The corrosion meter consists of an electrochemical cell in which coated metallic samples are tested in aqueous solutions. Furthermore, the corrosion meter has a holographic camera with a thermoplastic film for in situ processing holograms in order to obtain real time-holographic interferoms of the sample in the electrochemical cell.
During experiments, the samples remain in aqueous solution without any physical contact. In the meantime, corrosion data can be obtained from the interpretation of the interferograms of the sample as a function of the elapsed time of the experiments. Also, the open circuit potential of the sample is measured with respect to the interferometric data. Consequently, corrosion current density of Epoxy coated Aluminum, stainless steel, and low carbon steel in lM KCI, lM NaCl, and lM NaOH solutions were obtained by using the optical corrosion-meter. A comparison between the corrosion data of the different alloys slowed that the corrosion current density of the coated stainless steel in 1M NaCl is nearly three fold higher than that of the coated carbon steel in 1 M NaOH. In contrast, the coated Aluminum sample shows no sign of corrosion in 1M KCI .
In recent works published elsewhere, different techniques of optical interferometry have been found very useful in many applications in the field of electrochemistry for example, the technique of holographic interferometry was used to monitor the mechanochemical behavior, i.e. stress corrosion cracking, corrosion fatigue, and hydrogen embrittlement, of metallic electrodes in aqueous solutions 1?5.
The technique incorporates holographic interferometry for measuring microscopic deformation and electrochemical techniques for determining the corrosion current of metallic samples in aqueous solutions .
The objective of the present work was to monitor and measure corrosion of different metallic samples under coating in typical corrosive solutions by the technique of holographic interferometry . Furthermore, the work aimed to develop an optical corrosion-meter to measure the corrosion current density of an aluminum , stainless steel, and low carbon steel coated with epoxy -based coating in 1M KCI, 1M NaCl, and 1M NaOH solutions, respectively.
