The Research On Corrosion Behavior Of Steel Galvanic And Acoustic Emission

The construction of oil storage tank, not only promotes the rapidly development ofChina’s economy, but also brings the potential risk at the same time. The storage medium hascharacteristics of high temperature, high pressure, and high corrosion resistance etc. Especiallythe bottom of the tank is prone to rupture caused by corrosion damage. Acoustic emissiondetection technology is a new nondestructive detection technology, it has been widely used inthe tank bottom corrosion detection. This article mainly research on the mechanism of tankbottom corrosion, the characteristics of corrosion acoustic emission signal generation, andaccording to the characteristics of the acoustic emission signal to judge the corrosion process.This paper introduces the principle of the tank bottom corrosion mechanism and acousticemission signal generation. Due to the tank bottom withstand the weight of oil and its ownweight long time, at the same time, as the bottom plate and foundation such as changes indeformation, resulting in the tank bottom and the rain, dew or other electrolyte in directcontact with the electrochemical corrosion. Aiming at the tank material, the environment, andthe common corrosion types, this paper studies the acoustic emission mechanism of galvaniccorrosion of steel plate.Comprehensive analysis of galvanic corrosion mechanism and the principle of theacoustic emission signal generation, construct the simulation model by using the COMSOLfinite element simulation software. Simulate the expansion path and energy distribution of thelocal corrosion of steel plate flaw, descript the exchange current density during corrosion,galvanic corrosion velocity and electrode potential directly. The factors of the galvaniccorrosion are more complex, this paper aiming at the electrode material cathode and anodearea ratio simulation study. The results showed that, the maximum electrode current incoupled, so the metal dissolution at the point of maximum peak. Anodic exchange current incoupled at the electrode surface, due to the presence of pressure drop, so the way more farfrom the point, the exchange current density more law. With the loading time, exchangecurrent density at each point of the galvanic corrosion electrode has no obvious change. Underthe same conditions, galvanic corrosion phenomenon caused by anode area, the area greaterthe phenomenon more obvious. It means the unit time galvanic corrosion rate increases, but the two factors are not linear relationship. Analysis the result of the simulation, comparing theprinciple of the corrosion, verify the correctness of the simulation model, provide a theoreticalbasis for the experiments.According to the need of the subject the PIC-2acoustic emission detection system ofsteel were used in the air, in the10%Sodium Chloride Solution and the Steel-plate in the10%Sodium Chloride Solution by long continuous real-time detection. The results showed that, thecorrosion more serious, the more number of detected acoustic emission events produced bysteel plate unit time. Compared with the simulation results of galvanic corrosion, the resultsshow that the number of detected acoustic emission events in unit time could judge the rate ofgalvanic corrosion, and the quantity change could judge the trend of galvanic corrosion.