Study On Corrosion Of Coastal Steel Storage Tanks Influenced By Various Environmental Factors

With the rapid development of the oil industry and the energy demand,the reserves of crude oil and refined oil are widely concerned,and the reserves of other types of oil are also increasingly demanding.Most of the national oil reserve bases had established in China since 2003 are in coastal areas,and the corrosive environment is senior than inland.The service life of storage tanks is shortened.This can cause serious economic losses,even in the safe operation of a huge hidden dangers.Storage tank is not only an important part of the oil storage and transportation system,but also the main equipment indispensable to the production process.Therefore,it is of great practical significance to improve the design capability and construction level of China's tank design by providing a theoretical guarantee for the design,construction and selection of steel storage tanks in China by exploring the corrosion behavior under the influence of various environmental factors of coastal steel tanks.In this paper,the electrochemical experiment method was used to study the corrosion behavior of 16 Mn and Q235 materials used for steel tanks under different environmental conditions,such as oil,chloride ion,sulfur ion and bacteria.The experimental results show that the corrosion behavior of 16 Mn steel in petrol,diesel oil and heavy oil is controlled by the cathode reaction,because of the oxygen has different solubility in different oil.The corrosion rate of in petrol is the largest,followed by diesel,and the heavy oil.The corrosion current density of Q235 steel decreases with the increase of Cl-content in solution.When the Cl-concentration is more than 10g/L,the corrosion rate decreases with the increase of Cl-.The corrosion rate of 16 Mn steel in Cl-solution increases firstly and then decreases with the increase of concentration.In different concentrations of S2-solution,the corrosion rate of Q235 increases with the increase of S2-ion concentration firstly,and then decreases with the increase of S2-ion concentration.And the anode curve becomes more and more passive.When the concentration of S2-ions is more than 2.5%,the anode has a obvious passivation zone.With the increase of S2-ions,corrosion rate continues is accelerated.When the S2-content in solution more than 2.5%,although the corrosion current is still increased,the change is not obvious,A protective layer of the corrosion product is formed on 16 Mn steel.Cl-concentration has a significant effect on the corrosion behavior of Q235 steel in SRB medium.When the Cl-content in the solution is less than 50g/L,with the increase ofCl-content,Cl-with SRB promoted the corrosion of Q235 steel,and the corrosion rate of Q235 steel was accelerated.When the Cl-content is higher than 50g/L,the increase of salt concentration inhibits the growth of sulfate-reducing bacteria,and the corrosion rate of Q235 decreases with the increase of Cl-concentration.Different petroleum hydrocarbon degradation bacteria have different effects on the corrosion behavior of 16 Mn steel.16 Mn steel in ASW-3 in the largest corrosion rate,followed by ASS-2 and ASW-1 the slowest.In ASW-1 medium,with the growth and shedding of biofilm,the corrosion rate of 16 Mn steel decrease firstly and then increase;The corrosion rate of 16 Mn steel in ASW-3 medium change little;In ASS-2 medium,with alkali accumulation in the metabolic process,the corrosion rate of 16 Mn is significantly increase and corrosion rate becomes faster in 7days.