Effect of intermittent and continuous direct current electric fields on the initial corrosion of steel in simulated marine environment

Abstract

Increasing cases of accidents caused by the corrosion of new energy power equipment have appeared in coastal areas. The corrosion of coastal power equipment is not only influenced by temperature, humidity, and corrosive ions, but also by strong electric fields. To further understand the effect of electric fields on the atmospheric corrosion of metals in the context of new energy, the effect of an intermittent direct current electric field and a continuous direct current electric field on the corrosion of carbon steel was investigated using weight loss curves, polarisation curves, X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), and Energy Dispersive Spectroscopy (EDS) techniques. The main corrosion products include Fe3O4, γ-FeOOH, and α-FeOOH in the Cl− solution. The results demonstrate that the continuous electric field (CEF) promotes the growth of γ-FeOOH and inhibits the transformation from γ-FeOOH to α-FeOOH, leading to the formation of a loose corrosion layer. This layer is conducive to the diffusion of dissolved oxygen and accelerates steel corrosion. Due to the short action time of the electric field in the intermittent electric field (IEF), γ-FeOOH cannot crystallise continuously and gradually transforms to α-FeOOH, which leads to poor penetration of the rust layer. Additionally, the time with no electric field is short; therefore, the precipitation and adsorption of chloride ions cannot be realised, and the IEF slows the corrosion rate.