Characteristics of pitting corrosion in an existing reinforced concrete beam exposed to marine environment

•Corrosion pits are located next to the defects in concrete.•There are two types of pits: wide-shallow pit and narrow-deep pit.•An ellipse model is proposed to describe the shape of corrosion pits.•The growth trends of the wide-shallow pit and the narrow-deep pit are opposite.•The pitting factors are different between the wide-shallow and narrow-deep pit.