Device and method for testing electrochemical repassivation performance of metal material

Abstract

The invention relates to a device and a method for testing the electrochemical repassivation performance of a metal material, and belongs to the technical field of corrosion simulation experiments and transient electrochemical testing. The device mainly comprises a vacuum-tight box, a driving motor, a belt drive system, a rotary suction disc, an abrasive material fixedly arranged on the rotary suction disc, a metal sample clamp, a rotary cylinder, a horizontal translation cylinder, a vertical translation cylinder, a water bath system, a three-electrode electrochemical testing system. The testing process is carried out in an oxygen-free protection atmosphere environment in the vacuum-tight box, an oxidation film is removed from the surface of a passive metal sample by the abrasive material fixedly arranged on the rotary suction disc, then the sample is quickly soaked into a test solution, and the process of repassivating the exposed surface of metal from which a passive film is removed is monitored. According to the device and the method, different corrosion environments can be provided for testing the electrochemical repassivation performance of the surface of the film-free metal. An experiment result is true, stable and reliable, the automation degree of the operation is high, and the device is convenient to maintain and has an experiment standardization prospect.

Description

technical field [0001] The invention belongs to the technical field of corrosion simulation experiment and transient electrochemical test, and in particular relates to a metal repassivation performance test device and an experiment method. It is suitable for the electrochemical parameter test of the growth process of the passivation film on the surface of different metals fresh and without film, and can realize the simulation of different corrosion environments. technical background [0002] The passivity shown by passive metals (such as Fe, Cr, Ti, Al and their alloys) is due to the existence of a thin (nm or μm) dense metal oxide film on its surface, which is called passivation. film. This layer of dense passivation film can effectively prevent the direct contact between the metal and the corrosive environment, thereby isolating the metal substrate from the corrosive environment. However, in practical engineering applications, the passivation film layer is prone to def...

AI Technical Summary

Problems solved by technology

At present, the research methods on metal repassivation at home and abroad include: rapid tensile strain method (Engseth P, Scully J C. Corrosion Science , 1975, 15(6): 505-519.) By applying strain on the electrode, since the toughness of the oxide film is worse than that of the base metal, the oxide film ruptures first, so that the base is exposed to the corrosive medium and the passivation process occurs, but This method severely plastically deforms the test electrode, improves the electrochemical activity of the metal electrode, changes the electrochemical properties of the test electrode, and is unpredictable and controllable for the film rupture position and exposed area; the needle tip rapid scratch method (Burstein G T, Newman R C. Electrochimica Acta , 1980, 25(8): 1009-1013.) A scratch is quickly drawn on the flat metal by the diamond tip, so as to achieve the purpose of destroying the oxide film on the surface of the substrate, but there is a large elastic force in the local area of ​​the scratch position. Plastic deformation; indentation method (Fushimi K, Takase K, Azumi K, et al.. Electrochimica acta , 2006, 51(7): 1255-1263.) is that the oxide film on the metal surface is damaged or ruptured under the pressure of the insulating needle tip, exposing the metal substrate under the film. This method also has a large elastic-plastic deformation of the metal substrate influences

The shared problem of the above experimental methods is: in the process of removing the passivation film on the surface, the first exposed surface has actually undergone re-passivation reaction with the corrosive environment, while the re-passivation process of the subsequently exposed surface has not yet started

However, another unavoidable problem is introduced, that is, when the oxide film is removed, the substrate is easily recast in a local area of ​​high temperature under laser irradiation, which will fundamentally change the original microstructure of the metal material. and repassivation properties

[0004] In summary, the existing problems in the process of removing the passivation film on the original metal surface to obtain a freshly exposed film-free surface mainly include: large elastic-plastic deformation changes the electrochemical activity, uncontrollable exposed surface area, re-passivation The starting point of the process time is uncertain, and the recasting layer changes the microstructure and repassivation performance of the metal

These issues limit the understanding of the real repassivation transient process of metallic materials and the accurate evaluation of metal repassivation performance.

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