Method for testing electrochemical corrosion of welded pipe seam in high-stress state and sample of welded pipe seam

Abstract

The invention relates to a method for testing electrochemical corrosion of a welded pipe seam in a high-stress state, which utilizes an electronic universal testing machine, an electrolytic cell component comprising a working electrode, an auxiliary electrode, a reference electrode, a salt bridge and the like, and an electrochemical workstation. Under a load stress of between 0 and 800 MPa, the stress change caused by stress relaxation is corrected regularly by a constant potential method or a constant current method to test the circumferential tensile stress of the welded pipe seam and the circumferential tensile stress of the working electrode. A tensile sample is wide and thick at both ends and narrow and thin in the middle part and is provided with connection holes at both ends. A groove corrosion depth d1 and an average corrosion depth d2 of the working electrode are tested under different loads, so a groove corrosion susceptibility coefficient alpha, alpha=d1 / d2, of the working electrode in practical application can be obtained. The method has no stress relaxation, and the stress is convenient to regulate during test; the sample is free from generating plastic deformation or detachment under the load of high stress, and can be used for corrosion test under the condition of high stress; and the electrochemical workstation can be made full use for testing.

Description

technical field [0001] The present invention relates to a field of electrochemical corrosion measurement used in atmospheric erosion, corrosion or anti-corrosion measurement, specifically, the present invention relates to a method for measuring electrochemical corrosion under high stress state, more specifically, the present invention relates to a Method for measuring high stress state electrochemical corrosion of welded pipe welds and the specimens used. Background technique [0002] At present, due to the improvement of production technology and technology, welded pipes are more and more used in oilfield casings. The difference between welded pipe and seamless steel pipe lies in the weld performance of the two, especially in the corrosion resistance of the two. Now the electrochemical anodic oxidation method is generally used, and the groove corrosion sensitivity coefficient is determined by accelerated corrosion treatment. [0003] The stress state of the weld seam and ...

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Problems solved by technology

[0005] But, the problem that described method exists is: the method that adopts stress ring to load stress can not accurately display loading stress

[0007] The stress area of ​​the externally processed sample is large, and the stress area of ​​the thread is small. When high stress is applied, plastic deformation or even slippage will occur, and corrosion tests under high stress conditions cannot be carried out;

[0008] Although the electronic universal testing machine can accurately apply and adjust the target stress, there is a problem of electrical conductivity when this testing machine is connected to an electrochemical instrument, and the electrochemical workstation cannot be fully used for measurement;

[0009] In addition, the tensile specimens used in the above methods are prone to slippage during clamping, and cannot be loaded with high stress or damage the specimens

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