To explore the application of fluorescence elements in the field of corrosion monitoring, Ce doped YAG (Y3Al5O12) powder and coatings are prepared respectively. The effect of immersion duration in nitric acid is studied on the luminescent intensity. The results show that the YAG: Ce powder is mainly YAG phase. While the plasma sprayed coatings are dominated by YAG and YAP (YAlO3). The porosity and diffraction peak intensity of YAG: Ce coatings increase with the immersion duration in nitric acid. Meanwhile, the diffraction peak position moves for the coatings after they are immersed in the acid. The luminescent intensity of coatings increases firstly, and then decreases, and finally increases with the increment of immersion duration. The luminescent intensity of coatings is influenced by the porosity, crystallinity and phase composition of coatings etc.