Differentiating between the diffusion of water and ions from aqueous electrolytes in organic coatings using an integrated spectro-electrochemical technique

In this work, the separate diffusion of water and ions through a polyethylene glycol diacrylate (PEGDA) coating was characterized using an integrated spectro-electrochemical technique. The ions ingress front position profile along the thickness of the coating was derived from fitting odd random phase electrochemical impedance spectroscopy (ORP-EIS) data using a physically relevant electrochemical equivalent circuit (EEC). The arrival time of the ions at the coating/metal oxide buried interface obtained from EEC and rapid uptake of water was verified using in situ attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) measurements in Kretschmann geometry integrated in the ORP-EIS set-up.