Study of Cleaning Products Effect on Corrosion By Means of RGB Video-Electrochemical Techniques
Authors: Agrisuelas Jeronimo , Catala Marisa , Cuenca Alejandro , Lopez Celia , García Jose , Lorenzo Fernando , Vicente Francisco 
Published: February 2020

A digital endoscope camera with a USB connection was used to capture full-colored digital videos during spontaneous and electrochemical forced corrosions of technological metals digital videos at suitable regular intervals using a free software. The set of images, which included the complete interval time of the experiences, were automatically read and converted into intensity arrays by Mathcad® v14 software. After selecting the area under study, cropped images were decomposed into red, green and blue components as intensity subarrays using the Image Processing Functions included in the software. Values of arrays were classified between 0 and 255 intensity levels. Electrochemical experiments were performed with a PAR 273A potentiostat/galvanostat. The electrochemical cell was a 2×2 cm high-transmittance glass cell (Hellma, OG quality). Digital endoscope camera (EPA-503278) with USB connection was used to capture 640×480 color digital videos up to 30 framessecond. Digital images obtained from video were jpg RGB 8 bits per channel. The electrochemical cell was illuminated in a home-made white box with a T5 6400K fluorescent tri-phosphor lamp (color rendering index 80). An electrode of reference Hg/HgSO4/ K2SO4 (saturated) was used [1],

The results of this work shown as an example are the effect of some types of commercial industrial cleaning products that differ in the contents of aggressive substances such as peroxides, hypochlorite or chloride ion on three types of metallic materials widely used in industrial factory: aluminum, steels stainless steel and brass. The reference electrode Hg / HgSO4 / K2SO4 (saturated) was used.

For comparative purposes, the quantification of the potential for zero intensity prior to the anodic dissolution provides an approximate value of the corrosion potential. The height of the anodic dissolution peak gives an approximate value of the apparent corrosion rate. Both measures in potentiodynamic regime involve a rapid evaluation of the corrosion kinetics of the metal in the test media. The intensity changes in red (R), green (G) and blue (B) give a quantitative idea of changes in surface composition or within the dissolution. When convenient, the experiment can focus on the potential range of the anodic oxidation signal, at a maximum rate of 1 millivolt per second, and then calculate the exchange current (corrosion), the equilibrium potential (corrosion potential) and the slope of Tafel by a classical way.

Color histograms of RGB intensity subarrays showed the statistical distribution of Intensities-Red, green and blue component analysis from RGB digital image video opens up a new direction to evaluate and quantify the electrochemical corrosion of large electrode areas and to improve the inhibitors of corrosion and surface treatments fields.

RGB digital image video is a very versatile and low cost optical technique for investigating the electrochromic and corrosion processes. This mixed electrochemical-optical methodology can be especially indicated for the characterization of large surface samples, even dark substrates [2].

[1] J. Agrisuelas, J. J. García-Jareño, F. Vicente Spatiotemporal colorimetry to reveal electrochemical kinetics of poly(o-toluidine) films along ITO surface. Electrochim. Acta, 269 (2018) 350-358

[2] J. Agrisuelas, J.J. García-Jareño, E. Perianes, F. Vicente, Use of RGB digital video analysis to study electrochemical processes involving color changes, Electrochem. Commun. 78 (2017) 38–42.

This work was supported by Betelgeux -IVACE IMDITA2016/155 and MINECO-FEDER CTQ2015-71794-R