Wet chemical anodic oxides may represent an alternative way of forming passivating dielectric layers for silicon solar cells. In this paper we describe the requirements to achieve anodisation using a field-induced process which involves forward-biasing a p-n junction to make an n-type silicon wafer surface anodic. Although potentially very large currents can be achieved using this method, it is shown that the anodisation current is practically limited by the resistances in the electrochemical circuit. Furthermore, depletion regions can form at both surfaces when the wafer is under forward-bias. This can be addressed by either ensuring that the surfaces are sufficiently-doped for ohmic contact or by using light to generate a photocurrent in the depletion regions of the wafer.