Study On The Vapor Phase Inhibitor For Leave Unused Equipment Of Refinery

Corrosion and protection of idle equipment in refineries was considered as a big problem confronting the technician of this field. The application of vapor phase inhibitor shows that is more effective, and be available in use, comparing to the others of filling with nitrogen, oil, and drying agent. In the civil market, however, the vapor phase inhibitor for equipment in refineries is still lacking, so it is eager to develop such products.In this paper, a new vapor phase inhibitor (V2) used for idle equipment was tested based on selecting tests and mixing tests. Its performance was evaluated by static powder, dynamic powder and other common methods, good results were also achieved in actual plant test. Anti-corrosion mechanism of V2 vapor phase inhibitor was investigated by electrochemical analysis.Selecting tests showed, Although both Cyclohexylamine carbonate salt and Ammonium carbonate had excellent static or dynamic protecting effects for A3 steel, and there is not any rust appearance to be found in the surface of coupon sample, yet the volatilizing and weight loss is heavy; Dicycolhexylamine nitrite couldn't protect A3 steel effectively, corrosion was emerged in testing conditions; good inhibiting effect was get by the associated use of Sodium nitrite and Hexamethyleneteramine due to their synergistic inhibiting effects.Mixing tests results showed that V2 vapor phase inhibitor, which consisted mainly of inorganic ammonium salt and organic ammonium salts, was good in the property according to static and dynamic tests, its inhibiting effect was high to 98.5%, and would not cause corrosion when touched with steel. It volatilized quickly in short time and could maintain a long time, which prevented the equipment from corrosion not only in early but also relative long period.Results of sealing and keeping tests, electrochemical tests showed that the protecting efficiency of V2 vapor phase inhibitor to A3 steel and 16Mn steel was higher than any single ingredients, which proved that the ingredients in V2had obvious synergistic inhibiting effects each.Electrochemical tests were performed using self-designed cell, the proper design ensured good reappearance and average corrosion in surface. Advantage technology was adopted to reduce measure errors and promote accuracy and reliability.Electrochemical study showed, due to the fact of V2, the corrosion potential of 16Mn steel would drift +260mV, and corrosion current would drop from 172uA/cm2 to 4.86uA/cm2. Electrochemical inhibiting effect is 97.2%, so the mainly effect of V2 is to prevent anodic process, it is belong to anodic vapor phase inhibitor.Actual plant tests showed V2 was available for the protection of idle device in refineries, the inner surface of equipment and tower plate were not corroded, with the more than 10 month duration test, the coupon was shiny and corrosion rate is < 0.001 mm/a, inhabiting efficiency is >99%. In the other hand, V2 is cheaper than other products, so it can be commercially promising in the future. Such inhibitor also can be used for other steel equipments as well.