The ultrasonic detection of uniform corrosion in a thin sheet of aluminum alloy 2024-T3 was investigated at an early stage of corrosion damage. The artificial corrosion, similar to the corrosion in lap joints during operational service, was achieved using a corrosive solution as described in the literature. The corrosion damage intended was relatively weak when it has not yet caused significant changes of thickness and fatigue strength. On the other hand, it has caused significant changes of the intensity of transmitted ultrasonic waves. Maybe this effect can be related to the influence of corrosion damage on the attenuation of waves at the surface layer. The main results of the research shows that even small corrosion damage can be reliably detected by the integrated system (structural health monitoring) at an early stage of its development.