Finite Element Modelling of the Electrokinetic Mechanism of CRUD Deposition in Accelerating Flow

An electric model using the finite element method (FEM) has been generated to verify the electrokinetic phenomenon that has been postulated to be responsible for the localised corrosion deposition (CRUD) in the nuclear industry. The model shows that the acceleration of a resistive fluid through a micrometre scale pipe restriction leads to the spatial separation of anodic and cathodic sites. Specifically, an anodic region is formed at the inlet and it is spatially followed by a cathodic region; a second anode also forms next to the adjacent cathode. The streaming current in the electrical double layer (EDL) links the anode and cathode and it is also responsible for the generation of the current loops between the solution and electrode (the metal). The model predicts the local electrochemistry effect to deposition morphology of CRUD seen in power plants and in simulated experiments.