Method for evaluating corrosion resistance of welded joint based on potential testing technology

Abstract

The invention discloses a method for evaluating the corrosion resistance of a welded joint based on the potential testing technology. The method includes the following steps that 1, a welded joint sample is machined and then polished on a metallographic polishing machine, and the welded joint is corroded with a metallographic corrosion solution; 2, a proper welded joint corrosion solution is prepared according to the main influence factors in a service environment of the welded joint; 3, a saturated calomel electrode or a silver or silver chloride electrode is adopted in cooperation with a salt bridge, and a lower port of the salt bridge is closed with agar containing potassium chloride, wherein the caliber of the lower port ranges from 50 micrometers to 100 micrometers, and a saturated potassium chloride solution is contained in the salt bridge; 4, an experimental device is built, a drop of corrosion solution is dripped on the welded joint through a microinjector, the lower port of the salt bridge is adjusted to be immersed into the drop of the corrosion solution on the welded joint, and parallel mode or new area testing is performed; 5, indexes are evaluated. By means of the method, the problems that few evaluation methods for the corrosion resistance of the welded joint are available, and experimental testing devices are complex are solved.

Description

technical field [0001] The invention relates to the field of corrosion performance evaluation of metal materials, to the field of metal material welding technology and the field of electrochemistry, specifically a method for evaluating the corrosion performance of welded joints based on potential testing technology. Background technique [0002] Corrosion damage of steel structures is not uncommon, and corrosion failure of welded joints of steel structures is more common. The risk of corrosion damage to welded joints can be controlled to a certain extent by reasonable selection of welding consumables and control of welding process parameters. Few, China Classification Society's "Crude Oil Tanker Cargo Tank Corrosion-Resistant Steel Inspection Guidelines" mentioned a method of evaluating welded joints by metallographic step analysis, observing the junction of the welded seam and the heat-affected zone after corrosion under a microscope Whether there is a step, if there is a ...

AI Technical Summary

Problems solved by technology

The risk of corrosion damage to welded joints can be controlled to a certain extent by reasonable selection of welding consumables and control of welding process parameters. Few, China Classification Society's "Crude Oil Tanker Cargo Tank Corrosion-Resistant Steel Inspection Guidelines" mentioned a method of evaluating welded joints by metallographic step analysis, observing the junction of the welded seam and the heat-affected zone after corrosion under a microscope Whether there is a step, if there is a step and the depth of the step is large enough to form a discontinuous surface, it is judged that the corrosion resistance of the welded joint is unqualified. When judging the depth of the step, due to the uneven interface under the microscope, how to select The position of the interface causes large experimental errors. In addition, the selected welds and the junction positions of the heat-affected zone are different, and the depth of the test steps is not the same. The test error between parallel samples is relatively large.

Chinese patent CN201310339519.8 mentions a method for evaluating galvanic corrosion of welded joints by using modular array electrodes that simulate welded joints, and conducts electric spark cutting on welded joints to obtain small samples of weld seam, fusion zone, heat-affected zone, and base metal area , make an array of working electrodes, and adjust the area of ​​each area of ​​the welding joint through the number of working electrodes. This method is cumbersome in sample preparation, long in the test cycle, and high in test costs. It is not suitable for the rapid selection of welding materials and the formulation of welding process parameters. Test, Chinese patent CN201520115085.8 also mentions the method of using array electrodes to evaluate the galvanic corrosion sensitivity of welded joints. Multiple Q235 metal round rods are used to form an array electrode, and the working electrode uses a welded joint sample to realize the weld area of ​​the working electrode. , the current density distribution diagram of the heat-affected zone and the base metal area, and the sensitivity of the galvanic corrosion is evaluated by the coupled current density. Since the two poles of the galvanic couple are Q235 and the working electrode to be tested, they are different from the actual service environment of the welded joint. In addition, there are also literatures that point out the principle of potential test in the evaluation of corrosion performance of welded joints, but there are no specific evaluation indicators, and there are problems such as unclear operating procedures

[0003] In order to solve the problems of few methods for evaluating the corrosion performance of welded joints, complex experimental testing devices, unclear evaluation indicators, and inconsistencies between the evaluation results and the actual service environment results, the present invention provides a method for evaluating the corrosion performance of welded joints based on potential testing technology

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