Use of 8-hydroxyquinoline corrosion indicator in investigation of epoxy coated St-37

Fluorescent indicator can be used to detect the underlying corrosion on metal substrate based on forming complex with metal ions such as those generated from corrosion reactions. In the present work 8hydroxyquinoline (8HQ) was chosen as fluorescent indicator. The ion sensitivity of the indicator was investigated by fluorescent spectroscopy. Fluorescence emission intensity was observed to increase with increasing iron ions concentration. By incorporating 8HQ in to epoxy coated- St-37 system, it provided an early warning of corrosive conditions at the metal surface. The initial state of the coating system was nonfluorescent under UV light and it changes to fluorescent at the corrosion site. Bright corrosion sites were detected by fluorescent microscopy.