Atomic Layer Deposition of TiO2 Thin Films on the Inner Walls of Steel Tubes Increases Anti-coking Properties

To suppress catalytic coking, TiO 2 passivation films were deposited on the inner walls of SS316 stainless steel tubes by atomic layer deposition (ALD). Indentation test results showed a platform on the indentation curve of TiO 2 films grown over 2000 ALD cycles due to internal stress-induced microcracks. In coking experiments, the TiO 2 -coated tubes exhibited a higher heat flux and lower pressure difference than bare ones. Analysis of the coking surface revealed that TiO 2 thin film passivation can reduce the size and number of particulate deposits. At the same time, passivation treatment inhibits the formation of filamentous carbon and improves anti-coking performance by reducing the ability of the tube to adsorb amorphous deposition products. The coking surfaces of TiO 2 -coated tubes had less graphitization, indicating that the coking products had fewer defects and lower activated carbon contents.