Magnetic Field Effects on the Corrosion of Artificial Pit Electrodes and Pits in Thin Films

The effect of magnetic fields on localized corrosion was explored for one-dimensional artificial pits that are used to simulate pitting corrosion, and for two-dimensional pits in thin metal films.It was found that the pitting dissolution of ferromagnetic electrodes was significantly affected by the presence of a magnetic field.The presence of magnetic fields can lead to local stirring in the vicinity of artificial pits in ferromagnetic metals ͑iron, cobalt, or nickel͒ and pits in FeCo thin films, through the effects of the high field gradient force and the Lorentz force, causing an increase in the diffusion-limited current when the field is applied parallel to the dissolving surface.When the field is applied perpendicular to the dissolving surface, the field gradient force draws paramagnetic corrosion products toward the metal surface, protecting the metal from dissolution.The field gradient is, however, absent for paramagnetic stainless steel artificial pits, and the Lorentz force itself ͑in a field of 0.35 T͒ is insufficient to cause stirring within the pit cavities.Fields that are changing show a considerably bigger effect than static fields.