Due to new constraints in environmental legislation, it is necessary to develop suitable methods for the evaluation and the qualification of new protective paint systems. In particular, the need is high for investigating the protection performance of paint systems used in aggressive environments, such as environments of corrosivity category C5-M. The investigating method should be sensitive and relatively quick, give reproducible results and correctly discriminate paint systems. This paper presents results obtained on paint systems in the accelerated corrosion test according to ISO 20340 [1]. The evaluation technique as well as the criteria used for the acceptance of the aging test is discussed. From the results, it is clear that there is a need to develop or adapt sensitive tools to determine underfilm corrosion at early stages. In this view, the scanning Kelvin probe appears to be a promising tool to study the kinetics of delamination at the paint/metal interface.