Steel Corrosion in Submerged Concrete Structures-Part 2: Modeling of Corrosion Evolution and Control

A predictive model that simulates the sequence of events leading to the development of a stable corrosion distribution pattern in the submerged zone of a reinforced concrete column in a marine environment is described. The model incorporates potential dependent threshold (PDT) features that update the corrosion projection as additional parts of the system begin to actively corrode. Results are consistent with field observations reported in Part 1 and supported the interpretation that the passive state of a large portion of the steel can be preserved in the presence of high chloride concentration at rebar depth, even if typically assumed chloride threshold values were exceeded. In contrast, severe localized corrosion may take place elsewhere in the submerged region despite limited oxygen availability there. The calculations indicated that high concrete resistivity, which is typical in low-permeability concrete chosen for achieving long service life in the above water region, may under some circumstances promote unintended corrosion vulnerability of the submerged region by lowering the extent of beneficial macrocell coupling there. The model projected that sacrificial anode cathodic protection for partially submerged marine reinforced concrete structural elements could effectively control corrosion in the submerged region and to some extent in the lower elevation regions above water.