Corrosion Behavior Of Steel In Four High-sulfur And High Acid Crude Oil Fractions

With crude oil quality deteriorating continuously, acid and sulfur content rising, corrosion of crude oil and its fractions enhanced. Current research on corrosion behavior of high temperature crude oil mainly is naphthenic acid corrosion and sulfur corrosion.And in the top of the tower H2S-HCl-H2O system cause serious partial corrosion and rapid corrosion.The corrosion behavior of four steels used for crude oil distillation unit in high temperature crude oil fractions was studied through simulating the corrosive environment in atmosphere-vacuum distillation unit by using autoclave and weight loss method combined with the means of SEM and EDS analysis. In this study the effects of the crude oil fractions, material, and temperature on the corrosion behavior were analyzed. And analysis on the corrosion product film on the surface, high sulfur crude oil with high acid value of four kinds of material corrosion influence rule, and morphology and the chemical composition of the corrosion product film on the corrosion mechanism. The electrochemical corrosion behavior was studied by electrochemical tests in condensed waterAcid and sulfur can produce stronger corrosion of materials. The corrosion resistance degree:316L＞304＞1Cr5Mo＞20.Element Cr and Mo in the alloy steel are conducive to anti-corrosio. Corrosion rate of the four steel increased with the increase of the temperature, when the temperature is higher than200℃, the corrosion rate of20steel and1Cr5Mo steel increased rapidly, while the stainless steel at200℃corrosion rate increases with the temperature change is not obvious. When the temperature reached280℃sulfur began to participate in the reaction.Near the naphthenic acid boiling point temperature, increasing the reaction pressure will affect naphthenic acid gas liquid phase change.It makes the metal surface to form a layer of oily film that naphthenic acid concentration is higher.It significantly increased the corrosion rate of steels.In varying degrees, condensed water solution of H2S accelerated the corrosion of four kinds of materials. Corrosion product film have played an important role in accelerated corrosion. Especially20steel and1Cr5Mo steel are obviously. The impedance of the stainless steel has been as film-forming temperature increases.