Macrocell corrosion of reinforcement in marine structures.

The paper describes the setting up and execution of a full scale field test to investigate macrocell corrosion of reinforcement in a marine structure. The test involved the monitoring of corrosion currents and potentials in a 10 metre long concrete sample suspended vertically in the sea. An anode was formed by cracking the beam in the submerged section of the specimen. The construction and monitoring processes are described and a summary of results given. From the set of tests it was concluded that a macrocell was formed in the field sample with potentials and corrosion currents settling to values of -450 mV and 120 muA respectively. It was also concluded that the submerged region of the structure can be considered as virtually cathodically inert and that most of the current is drawn from the freshly aerated zone in an intertidal zone. After 14 months exposure the sample was recovered and sectioned for analysis. Examination of the recovered samples of reinforcement from the cracked area revealed magnetite filled corrosion pits with depths up to 4 mm. (A)