GB/T 13671-1992 Electrochemical test method for crevice corrosion of stainless steel
Some standard content:
UC: 669. 14. 018. 827 : 620. 193. 4U05
National Standard of the People's Republic of China
GB/T 1367192
Stainless steels-Method of eleclrochemicallest for crevice corrosion
Published on September 22, 1992bzxZ.net
State Administration of Technical Supervision
Implemented on July 1, 1993
WNational Standard of the People's Republic of China
Stainless steels-Methnd of electrochemicaltest for crevice corrosion
Subject content and scope of application
GB/T 13671—92
This standard specifies the principle, test instrument, sample preparation, test conditions, test steps and test report content of the electrochemical test method for crevice corrosion of stainless steel.
This standard is applicable to the evaluation of the crevice corrosion resistance of stainless steel in an oxide environment, especially for the comparison of different steel grades or different states. This standard is also applicable to the evaluation of the crevice corrosion resistance of metal materials implanted in human body surgery. 2 Reference standards
GB 626
Chemical reagents Nitric acid
GB1266
Chemical reagents Sodium chloride
GB 2477
Abrasive particle size and composition
3 Principle of test method
3.1 Use an existing artificial chain variable tool to connect a 1 cm stainless steel test surface with a nylon mesh artificial crevice, and place it in a constant temperature sodium chloride solution. Use a constant potential method to polarize it to 0.800 V\ to induce crevice corrosion. Note: ) The potential of the ground and the middle electrode of the 20-times-high electrode is the reference electrode, the same below. 3.2 After the crevice corrosion is induced, the potential is reduced to a preselected passivation potential. If the material is sensitive to crevice corrosion at this potential, the corrosion will continue to develop; otherwise, the sample will undergo re-passivation. 3.3 The most positive potential at which the crevice corrosion surface can be re-passivated is used as the criterion for evaluating the crevice corrosion resistance of the material. 4 Test apparatus
4.1 T crevice fixture, including organic glass fixture seat and gland, polytetrafluoroethylene gasket, nylon mesh and glass ball, see Technical Note A (Supplementary)
4.2 Single-channel constant potential instrument. One, or two single-channel potentiostats and external potential setters, or one dual-channel domain potentiostat. 4.3 XY recorder.
4.4 Glass electrolytic cell.
4.5 Constant temperature water bath.
4.6 Platinum auxiliary electrode.
4.7 Saturated calomel electrode and salt bridge.
5 Sample preparation
5.1 Sample size (mm): 10×10×8 or 11.3×8, 5.2 The sample material should be fully representative, that is, the chemical composition, heat treatment process and performance should be consistent with the use state. State Technical Supervision Bureau approved on September 22, 1992, implemented on July 1, 1993
WGB/T 13671--- 92
5.3 The sample is prepared by the machine processing method, and the test surface orientation should be consistent with the use state. Parallel test mixing is not less than three. 5.4 The test surface and the adjacent peripheral surface are carefully sanded with water sandpaper from coarse to fine, and finally polished and degreased with W28 water sandpaper in accordance with the provisions of (B2477).
5.5 The sample is passivated in 20%~30% chemical insulated nitric acid at 60℃ for 1h. 5.6 Connect the measuring wire to the reverse side of the test surface by soldering or spot welding. 5.7 Use rotten resin or other insulating resin to grid the sample, and expose 1 cm of the test surface (Figure 1). Medical quick test
Sample: 2 Insulating resin = 3 Plastic tube: 4 Conductor 5.8 Finally, the test surface is polished with W28 water sandpaper and cleaned with acetone and anhydrous ethanol. 6 Experimental
6.1 The test solution is 3.5% sodium fluoride solution. It is prepared by dissolving 35% analytical grade sodium fluoride in 965mL of distilled water or deionized water in accordance with GB 1266. The test temperature is 30±1℃6.2 The test solution for surgical implant metal materials is 9 g/L sodium chloride solution. The test temperature is 37 ± 1'C. 7 Test steps
7.1 Heat the electrolytic cell containing the test solution in constant temperature water to the test temperature and then keep the temperature constant. 7.2 Assemble the sample, put the sample into the fixture, soak the nylon mesh and the whole piece of polytetrafluoroethylene in the test solution, and then cover the test surface in turn, put the glass beads, and tighten the fixture. The pressure is positive when the hand does not move (see Figure 2). Figure 2 Assembled gap sample
1 Clamp pressure: 2 Clamp seat; 3 Glass beads; 4--Vinyl gasket + 5-Nylon mesh + 6-Embedded sample 2
WGB/T 13671
7.3 Place the assembled sample, auxiliary electrode and calomel electrode salt bridge into the test electrolytic cell. 7.4 Connect the measuring wires (see Figure 3 for the wiring of two single-channel potentiostats). After installation, the measuring film records the corrosion potential of the sample, V1. Figure 3 Schematic diagram of measuring wiring
1,2 Single-channel constant potential instrument: 3--Converter: 4 Electrolytic cell 5--Study electrode; 6 Reference electrode 7 Auxiliary electrode 7.5 Induce corrosion: Control the test potential at 0.800Ve and record the current-time curve. The sign of corrosion is that the current increases with time
When the current reaches 5(\u4 as shown in the a curve of Figure 4, immediately reduce the potential to V, (corrosion potential, that is, the first pre-selected potential). 7.5.1
7.5.2 The current may not reach 500μA, but increases with time as shown in the b curve of Figure 4. After 20s, reduce the potential to V1. 7.5.3 In the first 20 minutes, the current is very small (less than 4μA> or decreases with time as shown in curve c of Figure 4, and the induced corrosion time is extended. If corrosion occurs during the extended period, proceed as specified in 7.5.1 or 7.5.2 respectively; if no corrosion occurs after 16 minutes, the test is terminated, that is, the repassivation potential Vp>0.800Vn
time, and the corrosion occurs as shown in Figure 4.7.6 Repassivation of corrosion specimens: For the specimens that have been corroded, after the potential drops to the first preselected passivation potential, record the current-time curve and monitor for 15 minutes to determine whether it is repassivated. The sign of repassivation is that the current decreases with time or the current is very small (not more than 2μA, Figure 5); on the contrary, if the current increases with time (greater than 2±A) or fluctuates over a large range (more than 4μA, Figure 6), it means that there is no passivation and corrosion continues to develop. 3
W time, min
Gate 5 Passivation of the sample
GB/T 13671—92
Time, min
Figure Passivation of the sample
7.6.1 If the sample is passivated, the potential is raised to 0.00 V+ again to induce corrosion. 7.6.2 If the sample is not passivated and corrosion continues to develop, the test is terminated, that is, when the corrosion potential can no longer be passivated, 7.7 After inducing corrosion again (following the operation of 7.5), the potential is reduced to the second pre-selected passivation potential, V2. It is slightly positive than V, 0.05 (V) full scale. If V is -0.143V, then V should be -0.100 V. 7.8 Repeat 7.6 at the first preselected passivation potential. If no repassivation occurs, terminate the test, that is, V - V1. If repassivation occurs, repeat the operations of 7.5 and 7.6 until the sample no longer passivates at a certain preselected passivation potential, and terminate the test. Starting from the third preselected passivation potential V, each preselected value is 0.050 more positive than the previous one. 7.9 The potential for inducing corrosion is 0.800V and the preselected passivation potential V, V.·. are pre-adjusted in two dielectric constant potentiostats or two external devices or two channels of a dual constant potentiostat, and the potential conversion is instantaneous. 7.10 After the test is terminated, remove the sample and observe the test surface under a 20x magnification microscope to see if there is any corrosion, and make a record. 8 Test report content
8.1 Steel type number, name, chemical composition and production process 8.2 Corrosion potential V, Vua of each sample 8.3 The most positive potential V, Vxe of each test sample that can be repassivated after inducing corrosion. 8.4 The polarization current and time curves equal to and positive to the repassivation potential. 8.5. Describe the corrosion of the test surface.
WGB/T 13671-92
Appendix A
Artificial seam tunnel fixture
(Supplement)
A1 Organic glass center seat and pressure cover, see Figure A1 and Figure A2.122
A2 Polytetrafluoroethylene sheet, see Figure A3.
Organic corrugated glass fixture
Organic glass pressure gauge
A3 Textured woven nylon mesh (i.e. SP type), size ±15mm, specification 16, wire diameter 0.40mm. Not reusable. W. Glass beads, diameter 6mm.
Additional instructions,
GB/T13671—92
Figure A3 Polytetrafluoroethylene sheet
This standard is proposed by the China State Shipbuilding Corporation. This standard was drafted by Luoyin Ship Material Research Institute, Shanghai Ship Material Research Institute and Shanghai Iron and Steel Research Institute. The main contributors to this standard were Xu Xiaobei, Li Li, Xiao Jingxian, Liu Jingzhai, Zhao Aiwei and Mi Xiying.
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