Impact of magnetic field gradients on the free corrosion of iron

The influence of magnetic fields oriented parallel and perpendicular to the electrode surface on the corrosion behaviour of differently shaped iron samples in low concentrated sulphuric acid solutions has been studied. It is demonstrated, that the relative sample-to-magnet configuration, which determines the magnetic flux density distribution in front of the electrode surface, is decisive for the free corrosion activity. In a configuration generating low magnetic flux density gradients the Lorentz force driven micro-convection leads to an anodic shift of the free corrosion potential. In contrast, a configuration yielding high magnetic flux density gradients causes a cathodic potential shift and leads to a suppression of the corrosion reaction. These effects are discussed on the basis of the Lorentz force and the magnetic field gradient force acting on the partial reaction steps during the corrosion process.