Methods of seismic assessment of RC that find their way to practical application (see for example Eurocode 8-III) are calculation-intensive requiring extensive information about the layout and amount of reinforcement, in order to evaluate the dependable deformation capacity of the structural members to predict the performance in a future seismic hazard. Very little reference is made by the Assessment Guidelines to the condition of reinforcing materials, and the effect this may have on residual capacity, hierarchy of likely failure modes and the resulting implications on seismic performance. In fact, this is not a straightforward problem, as it induces an important level of uncertainty on the rather complex problem of calculating the response of poorly detailed reinforced concrete members under cyclic load reversals. This objective is pursued in the present study. The deprecating effects of corrosion-affected reinforcement on the mechanical response of a sample reinforced concrete element with substandard detailing representative of old practices and subjected to either moderate carbonation, or to cyclical chloride exposure for a period of 50 years (a sample of conditions in coastal urban areas build in the 70’s) is the reference case study. The column is examined under cyclic load reversals simulating low, moderate and intense seismic activity. The performance, expressed in terms of shear vs drift capacity is introduced in the available methodologies of rapid assessment of reinforced concrete structures showcasing the limitations and uncertainties of the existing state of the art in the field of seismic assessment of existing structures.