Modification of Rust Layer on Carbon Steel with Reactive Actions of Metallic Cations for Improved Corrosion Protectiveness Available to Purchase

In the present work, the modification of a rust layer on a carbon steel surface was examined during a cyclic corrosion test. The rust layer grown in a coastal region of Japan was used as a model rust layer. The x-ray diffraction analysis of the model rust layer revealed that the layer consisted of α-FeOOH, β-FeOOH, γ-FeOOH, and Fe₃O₄. During the cyclic corrosion test, an additional immersion of the surface in solutions containing metal cations such as Mg²⁺, Al³⁺, Cu²⁺, or Ni²⁺ was performed. The additional immersion in the cation-containing solutions modified the model rust layer, that is, the fraction of stable α-FeOOH increased in the rust layer. Furthermore, the modification of the model rust layer could suppress the corrosion of steel. The decreased corrosion rate was attributed to the suppressed cathodic reduction of the rust layers due to the presence of the stable α-FeOOH in the rust layers.