The process of transition from the passive to the active state by removal of the passivating film. A necessary condition for activation is an electrode potential negative to the equilibrium potential of formation of the passivating film. Activation is achieved by cathodic currents, by a reduced substance in the adjacent solution, or by contact with an electronic conductor having a suitably negative corrosion potential.
See also: passive state (in electrochemical corrosion), active state (in electrochemical corrosion)
PAC, 1989, 61, 19. 'Electrochemical corrosion nomenclature (Recommendations 1988)' on page 21 (https://doi.org/10.1351/pac198961010019)