Potential distribution characteristics of mild steel in seawater

Potential distribution of mild steel immersed in seawater for various periods was investigated by SMRE (scanning micro-reference electrode). For the coupons immersed horizontally, the edge was cathode while the middle was anode. When immersed vertically, the top of the coupon was the main cathode. After a period of immersion, the bottom became the main cathode. No matter how the coupons were placed, the composition of corrosion products in the cathodic area was β-FeOOH and Fe3O4 while in the anodic area was mainly γ-FeOOH. Relationship between potential distribution and corrosion products was discussed and the reasons for this phenomenon were analysed.

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► The edge was the cathodic area and the middle was the anodic area.
► The composition of corrosion products in the cathodic area was β-FeOOH and Fe3O4 while in the anodic area was mainly γ-FeOOH.
► Potential difference makes corrosion products different.