A pitting model has been developed which provides an explanation of why acetates affect CO2
pitting corrosion. The pitting diffusion model is based on the diffusion of iron ions from the bottom to the
top of the pit. To maintain electro-neutrality, negatively charged ions must migrate into the pit. For the
pit to continue propagating, it must be more acidic at its bottom than at the top. The model has shown
how acetates allow this to happen.
The new model can be used to predict if CO2 pitting corrosion will occur provided parameters
such as temperature, salt concentration, in-situ pH and acetate concentration are known. A method is
presented which allow for the calculation of in-situ pH from laboratory information.
Keywords: CO2 pitting corrosion, acetic acid, acetates, salt, in-situ pH