Fluorescent technology for corrosion prediction of aluminum alloys based on 8-hydroxy-quinoline

A fluorescent technology for corrosion prediction of aluminum alloys based on a coating containing a complex (AlQ₃) of aluminum ions with 8-hydroxy-quinoline (8HQ) was studied. The effects of aluminum ions and pH on the fluorescence characteristic of 8HQ were investigated. It was found that the intensity of AlQ₃ was increased with the concentration of aluminum ions. The 8HQ was embedded into the surface of the aluminum alloy and then further coated by a transparent epoxy coating to make samples. The samples made by this technology were exposed to a salt spray box. After salt spray tests, fluorescent spots were observed clearly under UV light whereas no obvious change was seen under visible light. The corrosion pitting on aluminum alloy substrates was observed at the fluorescent spots by an optical microscope. It was proved that the fluorescent spot size and intensity were increased with the aggravation and enlargement of corrosion area with corrosion time.