SY/T 0037-1997 Cathodic debonding test method for pipeline anticorrosion coating
Some standard content:
1 Scope
Petroleum and Natural Gas Industry Standard of the People's Republic of China Cathodic Debonding Test Method for Pipeline Anticorrosion Coating
Approval Department: China National Petroleum Corporation Date of Approval: 1997-12-31
Effective Date: 1998-07-01
This standard specifies the accelerated test method for determining the cathodic debonding performance of pipeline anticorrosion coatings. SY/T0037-1997
Replaces SYJ37--1989
This standard is applicable to the determination of the comparative performance of cathodic debonding of the outer anticorrosion coating of steel pipes with electrical insulation properties. These anticorrosion coatings are applied to buried pipelines with or without cathodic protection. This test method includes two test methods, A method and B method, which can be selected, but must be indicated in the test report. 2 Referenced Standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard was published, the versions shown were all valid. All standards are subject to revision, and parties using this standard should explore the possibility of using the latest version of the following standards. SY0066-1992 Nondestructive measurement method for thickness of pipeline anticorrosion layer (magnetic method) 3 Method Overview
3.1 The test piece is immersed in a highly conductive alkaline electrolyte, and the anticorrosion layer is subjected to electrical stress. The electrical stress is obtained by a magnesium anode or a forced current device. Before the test, the anticorrosion layer should be drilled into a defect hole. 3.2 In method A, a magnesium anode is used to provide a potential difference between the test piece and the anode, and no electrical monitoring is performed during the test. After the test, the test results are determined by visually checking the peeling area, that is, the effective adhesion of the anticorrosion layer to the metal surface is evaluated by checking the relative adhesion of the anticorrosion layer.
3.3 In method B, a magnesium anode or a forced current device is used to generate electrical stress, and the current and potential in the circuit are monitored by an instrument during the test. The test results are judged by visually checking the peeling area or detecting the current of the test piece, or both, but there is no correlation between the two methods. The current density value passing through the test piece in this test is much larger than the current density value required for the actual buried pipeline cathodic protection. Therefore, the current passing through the test piece can only be used as a relative indicator for qualitatively judging the peeling of the anti-corrosion layer. 3.4 To ensure the reliability of the test results, any reduction in the relative adhesion of the anti-corrosion layer considered in this test must be caused by electrical stress, and rain is not caused by other reasons. 3.5 The measured value adopts the legal measurement unit and is rounded to three significant digits. 4 Significance and Use
4.1 During the transportation and laying of the pipeline, it is almost inevitable that the anti-corrosion layer will be damaged. After the pipeline is buried, the anti-corrosion layer of the pipeline may be corroded at the damaged part due to the action of soil electrolytes. Normal soil potential and applied cathodic protection potential will cause the anti-corrosion layer to produce new leaks or loosen at the leaks. This test method provides a condition for accelerating the loosening of the anti-corrosion layer, which is used to determine the anti-loosening performance of the anti-corrosion layer.
4.2 The anti-cathodic stripping ability is a performance indicator obtained based on the comparison of the test pieces. Since all types of insulation that are currently used have peeling to some extent, the advantage of this test is that it provides a means of comparing one type of coating with another. Bond strength is more important to the inherent characteristics of some coatings than other properties, and even if two different coatings have the same peeling, it does not mean that they have lost the same anti-corrosion ability. 5 Reagents and materials 5.1 Electrolyte: It is prepared by adding 1% by mass of industrial pure anhydrous sodium chloride, anhydrous sodium sulfate, and anhydrous sodium carbonate to tap water, and it must be prepared before use. 5.2 Sealing materials for the ends of the test piece: Asphalt products, paraffin, epoxy resin, synthetic rubber or plastic can be used. 5.3 Test tank cover: It can be made of plywood or plastic board. Holes should be left on the cover for the test piece, anode, etc. to pass through. 6 Instruments and Equipment
6.1 Instruments and Equipment Common to Method A and Method B 6.1.1 Test Tank: A non-metallic tank made of non-conductive material or a metal tank lined with non-conductive material. The size of the tank shall meet the following requirements.
6.1.1.1 The specimen shall be suspended vertically in the tank, and the distance between its lower end and the bottom of the tank shall not be less than 25 mm. 6.1.1.2 The distance between the specimens, between the specimen and the anode, between the tank wall, and between the reference electrode and the anode shall not be less than 40 mm. 6.1.1.3 The volume of the test tank shall be determined in accordance with the requirements of 6.1.1.1, 6.1.1.2 and 7.4, and the height of the tank shall be such that the test section of the specimen can be immersed in the electrolyte
6.1.2 Magnesium Anode: Made of magnesium alloy, its potential in the electrolyte prepared according to 5.1 shall be between -1.45 and -1.55 V (CSE). The surface area of the anode shall not be less than 1/3 of the total immersion area of the test piece. The end of the magnesium anode shall extend out of the test tank cover. 6.1.3 Connecting wire: Insulated copper wire with a nominal core cross-section of not less than 2mm2. 6.1.4 Tools for drilling and visual inspection: Ordinary drill bits for drilling, with diameters as specified in 7.2; sharp knives with safety handles for visual inspection. 6.1.5 DC voltmeter: Internal resistance greater than 10MQ, range of 0.01~5V. 6.1.6 Reference electrode: Copper/copper sulfate (saturated) electrode, diameter should not exceed 19rnm, its potential relative to the standard hydrogen electrode is -0.316V. Saturated calomel electrode can also be used, but the observed reading must be added with -0.072V to convert it into a value relative to the copper/copper sulfate (saturated) electrode.
Note: In this standard, it is stipulated that the electromotive force of a primary cell composed of a standard hydrogen electrode as the cathode and a given electrode as the anode is the electrode potential of the given electrode. According to this regulation, the potential of the copper/copper sulfate (saturated) electrode and the saturated calomel electrode relative to the standard hydrogen electrode is negative. 6.1.7 Magnetic thickness gauge: measuring range is 1μm~～20mm, accuracy is ±2% of the range. 6.1.8 Mercury thermometer: range is 0~100℃, minimum graduation value is 1℃, length is 300mm6.1.9 Megaohmmeter: rated output voltage is less than 1000V, range is 0～2000MQ. 6.1.10 Metal electrode: stainless steel electrode can be used. Brass terminal; the diameter of the terminal should not be less than 6mm. 6.1.11
Plane planimeter: accuracy is 0.5%.
6.2 Instruments and equipment added in method B
6.2.1 DC voltmeter: internal resistance is greater than 10MQ, resolution is less than 10μV. Standard resistor: (1±0.01)2, power is not less than 1W. 6.2.2
6.2.3 Zero resistance ammeter: This meter should be able to measure DC current below 10μA. 6.2.4 DC regulated power supply: The output voltage is (3±0.01)V. 6.2.5 Auxiliary anode: A metal electrode with low consumption rate should be used, connected with a sealed insulated copper wire, or the upper end of the anode should be extended outside the slot cover. 6.2.6 Variable resistor: A 100Q winding potentiometer can be used, and its power should not be less than 3W. 7 Test piece
7.1 The test piece should be taken from an anti-corrosion pipe that can represent the industrial production situation, and one end should be sealed. 852
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7.2 One or three artificial defect holes should be drilled on each test piece, and three holes are recommended. Figure 1 shows the recommended size of the test piece. For single-hole specimens, the hole should be drilled in the middle of the immersion section; if three holes are drilled, the orientation of the holes should differ by 120°, the middle hole should be drilled in the middle of the immersion section, and the other two holes should be located 1/4 of the distance from the immersion line and the bottom of the specimen. Each hole should be drilled until the cone is completely inserted into the steel pipe wall and the edge of the cone is flush with the outer surface of the steel pipe. The diameter of the drill bit should be greater than three times the thickness of the anti-corrosion layer and should not be less than 6mm. The pipe wall must not be drilled through. For small-diameter specimens, a standard 60° drill bit can be used to start drilling, and finally a drill bit with the conical tip ground off can be used to complete the drilling. Sealed wire connector
12.7mm hole for pin
Comparison hole after test
Submerged wire
Detection hole on anti-separation layer
Detection hole
End seal
Plug or cover
Number in the figure
Detection hole
Recommended size
490.22±12.70
245. 11±12. 70
120.65±6.35
144.30±6.35
≥233.36
≥762
Figure 1 Recommended specimen dimensions
DD cut surface
Comparison hole after test
CC shaved surface
BB flipped surface
Testing hole
AA surface
SY/T 0037—1997
7.3 The end of the pipe extending out of the test slot cover can be supported by a pin passing through the upper end hole and connected to a separate wire for power supply and measurement. All connection points should be firmly connected by soldering, brazing or bolts, and protected and sealed with insulating materials. 7.4 The area from the end seal edge of the test piece to the flooding line is the test area, and the end seal area should not be regarded as the test area. The test piece can use an anti-corrosion pipe of appropriate diameter and length, but the immersion area should not be less than 2.3×10*mm2. When conditions permit, an area of 9.3×10*mm2 is the most suitable.
8 Test piece preparation
8.1 Before making an artificial defect hole, the continuity of the anti-corrosion layer and the effectiveness of the end seal should be checked according to the following requirements. 8.1.1 Immerse the test piece and the metal electrode in the electrolyte, connect one end of the megohmmeter to the test piece, and the other end to the metal electrode, measure the apparent resistance of the test piece, and then swap the connectors of the megohmmeter and measure again. The test result is expressed in megohms (M2). 8.1.2 Disconnect the test piece from the megohmmeter, immerse it for 15 minutes, and then test the apparent resistance of the piece again according to the requirements of 8.1.1. 8.1.3 If the apparent resistance of the test piece decreases significantly after 15 minutes, it indicates that there is a leak in the anti-corrosion layer or the end seal. If the leak is on the anti-corrosion layer, the test piece should be scrapped; if the leak is at the end seal, it should be repaired. After the repair is completed, retest according to the requirements of 8.1.1 and 8.1.2. 8.1.4 The lowest resistance value after immersion for 15 minutes should not be less than 1000M2. If the apparent resistance remains a stable value of less than 1000MQ in the tests before and after immersion for 15 minutes, it can be considered that there are no cracks or defects in the anti-corrosion layer and the test piece can still be used. All resistance test values should be listed in the test report.
8.2 Measure the thickness of the anti-corrosion layer of the test piece according to the provisions of SY0066, and record the average, minimum and maximum values of the thickness of the anti-corrosion layer and the thickness of the anti-corrosion layer at each artificial defect hole.
8.3 Record the original diameter of the artificial defect hole. 9 Test steps of method A
9.1 As shown in Figure 2, immerse the test piece and the anode in the electrolyte and connect them. The middle defect hole or the single defect hole should face away from the anode. Mark the position of the flooding line on the test tank and add water every day to maintain the liquid level. The temperature of the electrolyte should be maintained between 21 and 25°C. 9.2 Before the start and end of the test, the potential between the test piece and the reference electrode should be measured. During the test, the temporary wiring shown in Figure 2 is used, and its potential value should be between -1.44 and -1.55V (CSE). The reference electrode is immersed in the electrolyte only during measurement. 9.3 The test period should be 30d, and can also be 60d or 90d. 9.4 The following tests should be performed immediately after the test ends. 9.4.1 Take out the test piece and rinse the submerged area gently with warm water. Visually check whether there are new leaks in the submerged area and the loosening of the anti-corrosion layer at the edges of all leaks (including artificial defect holes). Record the condition of the anti-corrosion layer, such as color, bubbles, cracks, attachments, etc. 9.4.2 Use the position recommended in Figure 1 and the drilling method of artificial defect holes in 7.2 to drill a new comparison hole on the non-submerged anti-corrosion layer above the submerged line, about 1/2 away from the test tank cover and the submerged line. 9.4.3 Take the comparison hole and the artificial defect hole as the origin, and use a sharp knife to make incisions on the anti-corrosion layer around the hole according to Figure 3. Pay attention to ensure that the anti-corrosion layer is completely cut through to the surface of the steel pipe. 9.4.4 Use the tip of the knife to try to lift the anti-corrosion layer at the comparison hole and the artificial defect hole. Take the adhesion degree of the anti-corrosion layer at the comparison hole as a reference, and define the area of the anti-corrosion layer that is easier to lift or peel than the comparison hole as the peeling area. 9.4.5 Cover the artificial defect hole with translucent coordinate paper to draw the outline of the lifting area, and use a plane planimeter or the method of calculating the number of grids on the coordinate paper to obtain the lifting area of the artificial defect hole. Use the same method to obtain the lifting area of the comparison hole, and the difference between the two is the peeling area. 854
Gun-connected lugs
Connecting wire
Submerged wire,
Test section
Sealed end of test piece
Test apparatus for method A
DC voltmeter
Temporary wiring
Reference electrode
Test tank cover
Sealed in the power plant
Anode wire
Artificial defect hole
Magnesium anode
Test tank
Electrolyte
Figure 3 Cutout shapes of comparison hole and artificial defect hole 10 Test steps for method B
In addition to the tests in accordance with 9.1 to 9.3, the test should also be carried out in accordance with the following requirements. 10.1
SY/T 0037—1997
10.2 If a magnesium anode is used, the wiring shall be carried out according to Figure 4. If a forced current device is used, the wiring shall be carried out according to Figure 5 for a single specimen and according to Figure 6 for multiple specimens.
10.3 Without disconnecting the anode and the specimen, use a DC voltmeter to measure the potential E2 between the specimen and the reference electrode.10.4 Measure the current I1 between the specimen and the anode. It can be determined by measuring the voltage drop on the standard resistor with a DC voltmeter, or by a zero-resistance ammeter. That is, first connect the zero-resistance ammeter to both ends of the switch in the test circuit, and then disconnect the switch for measurement. After the measurement is completed, the switch should be reconnected and the ammeter should be removed. 10.5 Measure the polarization potential E1: Connect one end of the DC voltmeter to the reference electrode and the other end to the test piece. Disconnect the connection between the anode and the test piece. Watch the voltmeter closely. As the pointer of the voltmeter drops, it will pause at the polarization value. The voltage value at this pause point is E. 10.6 The electrical measurement value at the beginning of the test should be the average of the measurement results on the second and third days after immersion. The electrical measurement value on the day of immersion shall not be used for the calculation of characteristic values.
10.7 Electrical measurements should be made during and at the end of the test. The measured value should be the average of the measurement results on the specified date and the previous day. 855
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Immersed line
Artificial defect push
Figure 4 Test device for method BWww.bzxZ.net
DC voltmeter
Zero resistance ammeter
Test fine cover
Reference electrode
Magnesium anode
Electrolyte
Test tank
Immersed line
Artificial defect hole
DC voltmeter
DC voltmeter
1Q resistor
Test tank Benefit plate
Reference electrode
Auxiliary anode
Electrolyte
Test tank
Figure 5 Test device for method B when measuring a single specimen by the forced current method 10.8 The power supply of the DC regulated power supply shall not be interrupted. If there is an interruption, it should be noted in the test report. 10.9 Test according to 9.4.
11 Test report
11.1 The test report of method A should include the following: a) Complete identification information of the test piece:
① Name and anti-corrosion grade of the anti-corrosion layer,
② Outer diameter, length and wall thickness of the steel pipe,
③ Source, production date and batch number of the anti-corrosion pipe; ④ Maximum, minimum and average value of the thickness of the anti-corrosion layer and the thickness at the artificial defect hole;
③ Test area;
③ Diameter, area and number of initial artificial defect holes; ① Resistance measurement value of the continuity of the anti-corrosion layer and the effectiveness of the end seal. b) Date of start and end of the test, number of test days. c) The peeling area (mm) of the anti-corrosion layer on each test piece and its equivalent circle diameter (mm). If the test piece has multiple artificial defect holes, it is expressed as an average value. The equivalent circle diameter D is calculated using the following formula.
D= (A/0.785)1/2
--the area of one artificial defect hole, mm2. Where: A-
d) Other relevant information.
11.2 The test report of method B shall include the following: (1)
a) All data in the test report of method A. b) Electrical measurement results at the beginning of the test, on the specified dates during the test, and at the end of the test, including:
① The current IEI between the test piece and the anode in microamperes (μA)] and its negative logarithm -IgI [I, in amperes (A)]; 856
3W voltage divider
Auxiliary anode
Comparative electrode
Note: ① During the test, first adjust the DC power supply voltage to below 3 V, and then adjust each variable resistor so that the voltage at the A-C terminal is 1.5 V.
② During the test, the current is measured at the A-B terminal and the voltage is measured at the A-C terminal.
When multiple test pieces are measured by the forced current method
Test device of method B
② The difference between the potentials E2 and E: that is, △E-E, -E? The change values of △E, I and -lgI from the beginning to the end of the test. c) The number and time of interruptions of the DC regulated power supply. 12 Precision
SY/T 0037—1997
12.1 Precision data should be obtained from two adjacent test pieces on the same pipe with the same surface pretreatment and coating process and uniform anti-corrosion layer materials.
12.2 The test results should meet the repeatability requirements, otherwise the test should be repeated. When the test results are important or there is doubt about the results of a certain test, a reproducibility test should be performed.
12.3 The repeatability and reproducibility indicators of method A are as follows: Repeatability - When the difference between the equivalent circle diameters calculated by the same tester according to formula (1) is not greater than 12.7mm, the test result is credible.
Reproducibility
When the difference between the equivalent circle diameters obtained by the two laboratories is not greater than 25mm, the test result is credible. 12.4 In addition to meeting the requirements of 12.3, the repeatability and reproducibility indicators of method B should also meet the following requirements: Repeatability - When the difference between the values of -lgI, [I in ampere (A)] obtained by the same tester is not greater than 1, the test result is credible.
Reproducibility-----When the values of 1gI [I in ampere (A)] obtained by two laboratories differ by no more than 1, the test result is credible.
Appendix A
(Appendix to the standard)
Data sheet and report (format) for cathodic disbonding test of pipeline anti-corrosion coating A1 Common data sheet for Method A and Method B
1) Specimen number
First letter of specimen
2) Pipe
3) Anti-corrosion layer
Coating method
Thickness of anti-corrosion coating of specimen:
Thickness of anti-corrosion coating at artificial defect hole:
4) Test record
Start date
Number of test days
Report number
Report date
Manufacturer
Anti-corrosion grade
Production date
Coating equipment
End date
Test area
SY/T 0037--1997
Original diameter of artificial defect hole (mm)
Raised area of artificial defect hole (mm2)
Raised area of comparison hole (mm2)
Stripping area (mm2)
Equivalent circle diameter (mm)
Test time
At the beginning
After 15min
Data table for method B (see Table A3)
Data table for cathodic stripping test
2 Data table for apparent resistance test
Table A3 Cathodic disbonding test data sheet
Potential relative to the reference electrode
Test duration
Date and time
Change in the appearance of the test piece from the start to the end of the test: 858
Actual current 1
Each person
Defect hole
(average value)
Resistance value
Average value on the specified date
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