| Sulfuric acid manufacture device using sulphur and hydrogen sulfide is important to Petro China Yue Yang branch caprolactam production equipment. Smooth and safe running of sulfuric acid device can not only ensure the completion of the production plan, but also ensure the maximum economic benefits of the company.With the assistance of research team in the plant, the design data of the sulfuric acid plant, working conditions of the devices, and the corrosion products from the equiments have been investigated and collected.Using XRD, EDS, SEM and chemical analysis, corrosion products collected on the spot are analysed. With the calculation results of the thermodynamics software Factsage, and the analysis of the corrosion products, the causes leading to the corrosion of the sulfuric acid equipments havd been discussed in this paper. With the benefits of the latest researches on the corrosion mechanisms of equipments corrosion and analysis of the real cases, key factors to the corrosion of the equipments have been found and protective measurements are put forward in anti-corrosion suggestions. Mile steel Q235 and 20#, alloy 316L and ND steel have been tested by the electrochemical tests, immersion corrosion test, galvanic corrosion test in order to get the datas of corrosion resistance of the steels. Further studies in the corrosion mechanisms of steels in sulfuric acid have been taken, providing selection of the steels in equipment construction in the future.Corrosion happens in all of the equipments of the sulfuric acid including sulphur filler, heat exchangers and et al. The corrosion of E304 heat pipe economizer is the most severe.The main causes leading to corrosion of the sulphur filler has been found. First, the equipment is coverd by the sulphur dust on the surface. Second, Liquid membrane is formed, when vapor condensed into water. Third, the device is not coated with any protective coatings and exposed to industrial air. Through software simulation study and comparing with different types of experiment results, the main cause of the corrosion of the suphur filler was the atmospheric corrosion.E301 Superheater expansion joint is subjected to the sulphur corrosion by sulfur steam and produced sulfide at high temperature. Afterwards the sulfide reacted with sulfuric acid and caused sulfide cracking corrosion. Chemical corrosion happened in E303 medium temperature superheater by its working conditions. E304 heat pipe economizer is subjected to dew point corrosion caused by sulfuric acid by the inappropriate selection of equipment constructive steel, the unreasonable design of the equipment and the poor control of the production process. By immersion and electrochemical tests, it is found that when sulfuric acid concentration is lower than 60wt%, the corrosion rate of the metal increases with risen of temperature and concentration. ND steel and 316L have better corrosion resistance than carbon steel Q235 and 20 # steel. It was found that at 20℃, 316L has excellent corrosion resistance in all different concentrations of sulfuric acids. ND steel has better corrosion resistance than 316L in sulfuric acid at 60℃. in all kinds of tests, Q235 is superior to 20 # steel in corrosion resistance. But when ND steel, 316L attach to general structural steel such as 20# and Q235A in sulfuric acid, the galvanic corrosion will lower the corrosion resistance of the alloy steel, and increase the corrosion rate of the alloy steel, indicating that galvanic corrosion does weaken the corrosion resistance of all the tested steels.Against the mechanisms of the corrosion and causes of the corrosion, Anti-corrosion measurements are put forward in this paper. A Further look in relating research has been proposed in the end of this article.
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