Atomic Layer Deposition of TiO₂Thin Films on the Inner Walls of Steel Tubes Increases Anti-coking Properties

To suppress catalytic coking, TiO2 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 TiO2 films grown over 2000 ALD cycles due to internal stress-induced microcracks. In coking experiments, the TiO2-coated tubes exhibited a higher heat flux and lower pressure difference than bare ones. Analysis of the coking surface revealed that TiO2 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 TiO2-coated tubes had less graphitization, indicating that the coking products had fewer defects and lower activated carbon contents.