Atomic-level investigations of adsorption behavior of 1H- benzotriazole (BTAH) on Al surface are presented. Combination of reactive molecular dynamics method with experimental measurements is used for describing behavior of BTAH layer on oxide-coated Al surface upon contact with chloride-containing solution at 298 K. A thick BTAH layer formed on Al surface consists of two regions, a pseudo-monolayer at the BTAH/oxide interface and a loosely packed layer with randomly oriented BTAH molecules at the BTAH/aqueous solution interface. Physical adsorption dominates over chemisorption of BTAH to oxide-coated Al surface. Corrosion inhibition by a self-assembled BTAH layer was discovered. A protective action by the self-assembled layer was first detected by EIS data and then supported with analysis of electrochemical parameters by using equivalent electrical circuit (EEC) model to observe a strong capacitive behavior. Dissolution of BTAH layer becomes a critical factor controlling its inhibition action caused by weakening of intermolecular hydrogen bonding between BTAH molecules. Al-Cl bonds formed confirming pitting corrosion occurrence on oxide-coated Al surface. An increase in surface roughness with increasing immersion times was also observed for unmodified Al as well as for BTAH-modified Al surface.