Fluorescence based corrosion detecting epoxy coating
Therefore, to detect the onset of corrosion, a special substance was used in the coating at various concentrations. These substance was mixed into the resins which were characterized by various techniques (FTIR, NMR, TGA and DSC). Coated specimens were immersed in 3.5% NaCl solution and evaluated for corrosion resistance by electrochemical impedance spectroscopy (EIS). Modified coatings exhibit fluorescence upon interaction with ferrous ions releasing during the early stage of corrosion. The fluorescence response of modified coating was studied by using fluorescence spectrophotometer and confocal laser scanning microscope (CLSM). Corrosion resistance of coated specimens and fluorescent spots are correlated with respect to immersion time. Scanning electron microscopy (SEM) was used to reconfirm that onset of corrosion was took place at metal-coating interface. Modified epoxy coating possessing 10% w/w modifier has shown large number of fluorescent spots at the corroded regions as an early warning for the onset of corrosion.
a Naval Materials Research Laboratory, Ambernath (E), Dist. Thane, Maharashtra 421506, India; b Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India