Properties of Protective Films Formed on an Iron Surface by Dialkyl Phosphate as a Corrosion Inhibitor

Abstract

Abstract The properties of films formed on an iron surface by di-n-dodecyl phosphate were studied. The inhibition effects for iron specimens treated with dodecyl phosphate were estimated from the losses in weight of iron specimens in 5% NaCl aqueous solutions. The Fe Lα, Lβ X-ray emission spectra of the iron surface were obtained by electron microprobe X-ray analysis. The value of the intensity ratio, Fe Lβ/Lα, of the untreated iron specimen was 0.17, while that of the treated iron specimen was 0.28. The infrared spectrum of the treated iron surface was similar to that of tribasic orthophosphate. The content of Fe in the film formed on the iron surface by di-n-dodecyl phosphate was from 4.3% to 6.98%. From these results, it was inferred that di-n-dodecyl phosphate reacted with iron atoms at the iron surface in a cyclohexane solution and that the main component of the film formed on the iron surface was [(RO)2POO]2Fe or [(RO)2POO]3Fe.