| With the rapid development of the construction of crude oil storage tanks in China, it has attracted wide attention with the serious harm caused by the corrosion of the tank bottom. Corrosion monitoring technique provides corrosion performance in real-time and sends out early warnings of costly corrosion damage. The paper studied the EIS of the coating system which consisted of epoxy zinc-rich coating as a primer and bituminous epoxy coating as top coat in accumulated water from crude oil storage tank, and developed a kind of coulostatic corrosion monitor which used for corrosion detection of the bottom of the oil tank. The detailed research and results were summarized as follows:The coating system commonly uesd in the crude oil storage tanks was selected. The coating system on the surface of the carbon steel consisted of two parts, epoxy zinc-rich coating as a primer and bituminous epoxy coating as top coat. The paper studied the EIS of the coating system in accumulated water from crude oil storage tank, and put forward the equivalent circuit models of the coatings during the course of immersion. The relation between the characteristics of EIS and the structure of coating system was discussed. The results showed that it can reflect the corrosion process of the coating system from the characteristics of EIS, and provide reference for the maintenance of the coatings on the bottom of the crude oil storage tank.Coulostatic test technology has the advantages of high testing speed, no effects with the solution resistance and continuous real-time monitoring, and the instrumentation is simple in principle. The paper developed a kind of coulostatic corrosion monitor. The hardware system included four parts, which were CPU and the communication circuit, electrochemical interface circuit, signal amplification circuit and A/Dã€D/A conversion circuit. The interaction between the circuits was completed by bus. The circuits debugged successfully formed the hardware system.The Software development used structured design. The structure of the main program was clear, and the Software completed the corresponding function by calling the subfunction. All program modules had been linked into an executable files after compiled separately, then copied to EPROM. The program of PC was written by Visual Basic which is a visual programmable language with the character of user-friendly interface and easily-operation. The program of the microcomputer application system was written by assembly language. The Coulostatic test can be controlled by MCU or PC. The Communications between PC and monitor was realized through serial communication interface, and by software polling in accordance with common protocol. The simulation experiment based on equivalent circuit was carried on and the results can satisfy the request of the corrosion monitoring in industry. |
