  In this paper we advance a stiff solution dynamics [SSD] model to study the
regulation of local chemistry near a corroding metal by reaction and diffusion
processes in the electrolyte. Using this model we compute the detailed
space-time dynamics of the concentrations of metal ions, its hydroxy complexes,
H+ and OH- ions near the corroding metal. The time for the onset of passivity
for Fe and Zn is presented for free corrosion condition, different impressed
currents and initial pH values. The theory advanced provides much physical
insight into corrosion and passivity of metals and motivate
spectro-electrochemical studies.
