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Crude oil tank bottom corrosion is always a major problem in China's petrochemical enterprises one of the issues. Crude oil itself is not highly corrosive, the problem mainly from crude oil mixed with water and corrosive impurities, heavy oil floats over a long period of water deposited on the bottom of the tank. Deposition of complex components in water, but also contains a variety of microorganisms; floating roof tanks uprights shock and vibration, fluid turbulence phenomena, and also allows the corrosion plate adds mechanical factors; floating roof tanks under the floor uprights severe corrosion, and and crevice corrosion significantly correlated. In this thesis, oil jars bottom water corrosion mechanism launched a systematic and comprehensive study, as follows: Test methods studied by electrochemical Cl - , S 2 - , temperature, pH value on the polarization behavior of A3 steel and carbon steel materials tested different polarization curves of the water during the deposition. The results show that the deposition of carbon dissolved in the water in the active state; Cl - ions will not only accelerate the anodic dissolution of carbon steel, but also affect the behavior of carbon cathode: S 2 - ions both may play a protective role, but also may accelerate the corrosion properties of the medium and the generation which forms sulfide closely linked; neutral and alkaline media corrosion of carbon steel is not, and medium acidity and temperature will accelerate corrosion. Simulation test device was designed to study the different loading cases, the impact of vibration on carbon steel corrosion and crevice corrosion test carried out. The results show that a simple pressure no serious corrosion of carbon steel, but the vibrations can accelerate corrosion and wear, debris and accumulation of corrosion products, resulting in uneven distribution of this region, resulting in severe localized corrosion. Simply containing SRB (SRB) medium corrosion of carbon steel is not obvious. AC impedance studies have found, Fe 2 ion content of carbon steel corrosion SRB great impact, when Fe 2 ion content in 2-20mg · L -1 , the main form of corrosion of steel surface pitting, in the absence of Fe 2 ions or Fe 2 ion concentration is high (120mg · L < sup> -1 ), the steel surface to uniform corrosion mainly produces no pitting. Meanwhile, the study also uses dynamic polarization curves of bacterial corrosion product - sulfide film formation process in pitting the role, and found that when the potential is greater than-0.17V (break potential), the steel surface into the stable pitting area . Through the mechanism of corrosion, oil tank bottom corrosion perforation corrosion caused mainly by the physical and chemical abrasion damage, followed by crevice corrosion and bacterial corrosion caused by SRB synergistic corrosion. In the mechanism, based on the crude oil tank bottom can be taken on the various protection schemes are compared, that the paint is most suitable sacrificial anode joint protection and paint protection for the joint selection carried out further research and found that guide the University, Zhejiang University Master Thesis will accelerate the use of electrostatic coating sacrificial anode dissolution, the impact protection efficiency, according to the oil tank bottom in a special environment, long-term immersion in the deposition of the water, so you can consider using an insulating coating, which can save the amount of sacrificial anodes and achieved good protective effect.
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