Coupled erosive behavior of naphthenic acid and sulfur at high temperatures

Naphthenic acid and sulfur exist simultaneously during the refining process, and so its coupled coordination corrosion affects the manufacture of oil refining enterprises. By simulating the corrosion of oil field, the coupled coordinated corrosion research of naphthenic acid and sulfur was carried out in high-temperature reactor, and then the corrosion products were analyzed by EDS and XRD. The results show that at high temperature, in sulfur only medium, the corrosion rate of two kinds of steels increases firstly and then decreases with the increase of mass fraction of sulfur; in the condition of coupled coordinated corrosion, when sulfur content is 1% (mass fraction), with the increase of acid value the corrosion rate of Q235 increases all the way, and the increase tendency of corrosion becomes bigger when acid value is over 9 mgKOH · g-1; while the corrosion rate of 316 steel increases firstly, decreases secondly and then increases, so 316 steel has two critical acid value of 9 mgKOH · g-1 and 12 mgKOH · g-1; when acid value is 9 mgKOH · g-1, with the increase of mass fraction of sulfur the corrosion rate of 316 increases firstly and then decreases, while Q235 increases all the way; after analyzed the corrosion films, found that the corrosion film of Q235 steel has crumbly Fe7S8; sulfur content, acid value and temperature affect the corrosion membrane morphology of coupled coordinated corrosion.