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

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 spectroscopic techniques (energy dispersive X-ray (EDX), X-ray photoelectron (XPS), and far-infrared reflection absorption (RAIRS) spectroscopies) and polarised neutron reflectometry (PNR). Although there was no observable affinity of BEHP to the steel surface in dry solvent, a layer of rough iron (III) phosphate formed in water-saturated dodecane. The phosphate-reacted steel surface showed some resistance 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 a viable phosphating agent for steel surfaces. [Display omitted] •Bis(2-ethylhexyl) phosphate indifferent to steel/iron surface in dry dodecane•Organic phosphate-steel reaction immediately initiated on addition of water.•Iron (III) phosphate layer forms from reaction and provides corrosion protection.