In order to characterize the properties of film/metal interfaces formed between plasma-polymerized amorphous silica-like (a-SiO2) films and metal substrates, lap joints and wedge test specimens were made from aluminum and titanium adherends that were pretreated with plasma-polymerized a-SiO2 primer films. High breaking strengths of all the lap joints due to cohesive failures within the adhesive indicated that the adhesivela-SiO2 and a-SiO2/metal interfaces were very strong. In addition, since failure was cohesive within the adhesive, the different interfacial structures at the a-SiO2/aluminum and a-SiO2/titanium interfaces were cohesively strong. In order to maximize the environmental stress placed upon the a-SiO2/metal interfaces, the a-SiO2 primer films on the metal adherends were pretreated with silane primers before adhesive bonding. This ensured that differences in environmental durability at the a-SiO2/metal interface, if any, would be observed. However, no interfacial failures of pretreated substrates was observed, indicating that the a-SiO2/aluminum and a-SiO2/titanium interfaces had very high environmental durability. This correlated well with the results obtained in Parts I and II of this work, which supported the formation of strong Al-O-Si and Ti-O-Si bonds at the a-SiO2/metal interface.