Corrosion inhibition of steel in seawater through surface phosphate formed from oil

To assess the molecule’s effectiveness as an anti-corrosion additive, bis(2-ethylhexyl) phosphate (BEHP) was exposed to carbon steel surfaces from dry and water-saturated dodecane. The resulting changes to the surfaces were characterised using energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), polarised neutron reflectometry (PNR), and far-infrared reflection absorption infrared spectroscopy (far-IR RAIRS). We conclude that, although the BEHP molecules showed no observable affinity to the steel surface in dry solvent, a layer of rough iron (III) phosphate formed in water-saturated dodecane. The phosphate-reacted steel surface was resistant to corrosion by seawater, suggesting the formation of a cohesive barrier against corrosive species. The results support the use of BEHP as an anti-corrosion additive and suggest it is a viable phosphating agent for steel surfaces.