Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《中国腐蚀与防护学报》
Abstract： 316L stainless steel is widely used for enhancing the pitting resistance of pipelines in gas field. The corrosion environment is complex and diversified in different working districts of gas field. Therefore, it is necessary to develop a model for predicting the pitting resistance of pipelines serving in different corrosive environments. Critical pitting temperature (CPT) is considered as a criterion for evaluating the pitting resistance of stainless steel. Based on a survey on the operation situations of gas field, the relevant data of CPT for 316L stainless steel is acquired by potentiodynamic polarization method in solutions with various Cl- concentrations and pH values, which are selected to correspond with the real environments in operation. Then, an artificial neutral network (ANN) model is developed to predict the CPT, and therewith to compare with the measured data. The results show that the CPT decreases with the increase of Cl- concentration, but on which pH value has little influence. The developed ANN model has good ability to predict the CPT of 316L stainless steel, and can be used for the prediction of CPT in complex environments in gas field. It is also revealed that there is no interactive effect between Cl- concentration and pH value, and Cl- concentration was the main influencing factor on the CPT. Therefore, Cl- concentration will be peculiarly concerned with for the implementation of a corrosion control project in gas field.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract： Incident involving failure occurred for a 40 months old upright type tee of gas filed gathering and transmission pipeline in a west natural gas field. The tee consisted of a main pipe of 16Mn steel and branch pipes of bimetal composite of 316L stainless steel+L416 steel. Examinations were performed to identify the cause of the failure, which include visual physical inspection, pipe thickness measurement and acquiring the galvanic corrosion behavior of 16Mn steel and 316L stainless steel in an oxygen-free medium containing chloride ion concentration 150 g/L with CO2 partial pressure 0.1 MPa at 65 ℃ using electrochemical methods, as well as Computational Fluid Dynamics (CFD) analysis of the tee with assumed angles as 90°, 45°and 30°respectively between the branch pipe and main pipe along the direction of inlet using the FLUENT software. Investigations revealed that for the present tee design, there existed galvanic couple of the metallic materials and the straight cutting structure of the tee caused the fluid changes radically. Gas field water gradually adhered to the inner side of the pipe due to the low velocity that caused by the vortex which was formed nearby the pipe explosion site. Corrosion then ensued as CO2 dissolved in the water. The area around the explosion site suffered from large wall shear stress caused by the fluid scouring action. Because of the synergy of galvanic corrosion and fluid flow erosion the pipe gradually thinned, and then perforated.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract： Epoxy coatings with different additives of phytic acid were applied on rust and sand-blated Q235 carbon steels respectively. The adhesive strength and corrosion perfromance of these coatings were studied by means of adhesion measurement and electrochemical impedance spectroscopy (EIS). The results showed that the adhesive strength, corrosion resistance and the barrier effectiveness of the epoxy based coatings could be enhanced by the addition of phytic acid in the epoxy varnish. Moreover, phytic acid could inhibit the corrosion of the metal beneath the coating. The coating containing 3% phytic acid had the best corrosion perfromance.
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-12 Cooperative journals: 《中国腐蚀与防护学报》
Abstract：本文初步回顾了近年来电化学噪声分析方法的若干研究工作，举例介绍了电化学噪声数据直流漂移、电化学噪声时-频分析、非线性分析和模式识别等分析方法的优缺点，并对电化学噪声分析方法的发展方向进行了展望。
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