The corrosion of mild steel in contact with seawater and sand

This paper presents selected results from an experimental study of the corrosion of mild steel in contact with chemically inert particles and seawater. Mild steel coupons were buried in particulate media in coupon containers and then immersed in seawater tanks for set periods of time. The full study considers a number of parameters including burial type, pollution level, particle size, and exposure period. The present paper presents mass loss and pit depth results for coupons buried in sand (either completely or partially) and immersed for up to 8 months in seawater dosed with nutrients. The results are compared with corrosion loss and pit depth observations at 20 years exposure on seabed chains in the North Sea. For the present study the coupons partially buried in sand showed the greatest mass loss and the deepest absolute penetration. Coupons that were completely buried showed the least mass loss. The greater mass loss was associated with greater access to oxygen available at the surface of the metal. Reasons and implications are discussed.