SY/T 0094-1999 Cathodic disbonding test method for pipeline anticorrosion coatings - bonding electrolytic cell method SY/T0094-1999 Standard download decompression password: www.bzxz.net

1 Scope
Petroleum and Natural Gas Industry Standard of the People's Republic of China Cathodic Debonding Test Method for Pipeline Anticorrosion Coating
(Bonded Electrolytic Cell Method)
Approval Department: State Administration of Petroleum and Chemical Industry Date of Approval: 1999-05-17
Effective Date: 1999-12-01
This standard specifies the accelerated test method for determining the cathodic debonding resistance of pipeline anticorrosion coatings. SY/T 0094—1999
This standard is applicable to determining and comparing the cathodic debonding resistance of the outer anticorrosion coating of buried steel pipes with electrical insulation properties, and is also applicable to the determination of the cathodic debonding resistance of the anticorrosion coating when the entire test piece cannot be immersed in the test solution. 2 Referenced Standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards are subject to revision, and parties using this standard should explore the possibility of using the latest versions of the following standards. SY/T0063—1999 Test method for leak detection of pipeline anticorrosion layerSY/T0066—1999 Nondestructive measurement method for thickness of steel pipe anticorrosion layer (magnetic method)3 Method overview
3.1 This test method is to adhere the test electrolytic cell to the surface of the test piece coated with the anticorrosion layer. The shape of the test piece can be flat or curved, and it should not deform during the test.
3.2 Before the test begins, drill an artificial defect hole in the anticorrosion layer, and then make the anticorrosion layer on the test piece subject to electrical stress in a highly conductive alkaline electrolyte solution, and the electrical stress is obtained by an external DC power supply. 3.3 In this test method, the current density value passing through the test piece must be greater than the value required for the actual buried pipeline cathodic protection. 3.4 During the test, a high-resistance multimeter is used to detect the potential between the test piece and the reference electrode and the current passing through the test piece. 3.5 At the end of the test, the test piece is inspected, that is, the cathodic debonding resistance of the anti-corrosion layer is evaluated by comparing the degree of debonding of the anti-corrosion layer at the artificial defect hole in the unimmersed area of ​​the test piece with that in the immersed area. 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, due to the action of the soil electrolyte, the pipeline anti-corrosion layer may be corroded at the damaged part. The application of cathodic protection potential will cause new leaks or debonding at the leaks. This test provides a condition that accelerates the debonding of the anti-corrosion layer, so as to determine the anti-debonding performance of the anti-corrosion layer. 4.2 The test results are judged by physical inspection or by checking the current passing through the test piece. Usually, there is no correlation between these two methods. The physical inspection method evaluates the effective adhesion between the anti-corrosion layer and the metal surface by the difference in relative adhesion observed. The area with adhesion less than the original level is the cathodic debonding area. 4.3 The anti-cathodic debonding performance is a performance index obtained based on the comparison of the test pieces. The advantage of this test is that it provides a means to compare one anti-corrosion layer with another. 913
SY/T0094—1999
5 Instruments and equipment
5.1 Test container: A transparent plastic tube or glass tube, which is sealed with a waterproof sealing material on the surface of the test piece centered on the artificial defect hole. The inner diameter of the sealed container is not less than 100 mm, and the height for holding the electrolyte solution is 130 mm. 5.2 Anode device: The anode device consists of a filter tube with a microporous diaphragm and a forced current anode. Its structure is shown in Figure 1. During the test, the anode device is suspended in the test container, with its lower end located 25 mm above the artificial defect hole and the edge 13 mm horizontally away from the defect hole.
Pick welding or bolting
Connect to the positive pole of the power supply
Platinum anodewwW.bzxz.Net
Electrolyte
Glass test tube
Microporous membrane
Figure 1 Anode device
5.2.1 Filter tube: It consists of an immersed test tube with a microporous membrane. The test tube is 180mm long and 8mm in diameter. The diameter of the microporous membrane is 30mm, and the diameter of its micropores is 10-15μm. 5.2.2 Forced current anode: A 0.5mm diameter wire platinum anode, which should be long enough to extend out of the test container and be connected to the wire of the DC power supply through bolts or clamping devices. The distance between the platinum anode and the bottom of the filter tube is 5mm. 5.3 Reference electrode: Saturated copper sulfate electrode, the diameter should not exceed 19mm. Saturated calomel electrode can also be used, but the observed readings must be converted to values ​​relative to the saturated copper sulfate electrode. 5.4 High resistance multimeter: a multimeter with internal resistance not less than 10MQ, capable of measuring a minimum 1mA DC current and a maximum 10V DC voltage. 5.5 DC power supply: a low ripple DC power supply device capable of polarizing the test piece to a potential of 3V±0.01V relative to a saturated copper sulfate reference electrode.
5.6 Standard resistor: 1Q±0.012, power not less than 1W. 5.7 Magnetic thickness gauge: in accordance with the provisions of SY/T0066. 5.8 Anti-corrosion layer leak detector: in accordance with the provisions of SY/T0063. 5.9 Connecting wire: insulated copper wire with a nominal core cross-section of not less than 2.5mm2. 5.10 Industrial. True: an electric drill equipped with a 3.2mm diameter ordinary drill bit, and a sharp knife with a safety handle. 914
6 Electrolyte solution
SY/T 0094—1999
Mass fraction 3% sodium chloride solution: Prepared by adding analytical pure sodium chloride to distilled water or deionized water according to the mass ratio, and must be prepared before use.
7 Test piece
7.1 The test piece can be taken from the anti-corrosion pipe produced by industry, or the pipeline in operation or any suitable anti-corrosion layer surface. The shape of the test piece can be flat or curved.
7.2 The distance between the test area on the test piece and all cutting edges should not be less than 75mm. When cutting the test piece, measures should be taken to reduce the damage to the anti-corrosion layer caused by heat conduction and splashing. 8 Test steps
8.1 Inspect the integrity of the test area of ​​the test piece's anti-corrosion layer according to the relevant provisions of SY/T0063. The test piece without leakage is qualified. Measure and record the maximum thickness, minimum thickness and average thickness of the anti-corrosion layer in the test area according to the provisions of SY/T0066. 8.2 Use a common drill bit with a diameter of 3.2mm to make an artificial defect hole on each test piece. The cone tip of the drill bit should completely enter the steel, and the cylindrical part of the drill bit should contact the steel surface. 8.3 Connect the test circuit as shown in Figure 2. All connection points should be firmly connected by soldering, brazing or bolts, and protected and sealed with insulating materials.
1Q resistor
Support
Microporous diaphragm
Sealing glue
Platinum anode
Glass test tube
Electrolyte solution
Artificial defect hole
Transparent plastic tube
Or glass tube
1Q resistor
Connect to positive pole of power supply
Glass test tube
Electrolyte solution
Connect to negative pole of power supply
Sealing glue
Figure 2 Test device
Artificial defect hole
8.4 Glue the test container to the test piece as shown in Figure 2. The shape of the bottom of the container should match the surface of the test piece to ensure a good seal. The position of the container should make the artificial defect hole in the middle. 8.5 Add the electrolyte solution to the specified height (130mm) of the test container, record the pH value of the solution, check the height of the solution every day, and maintain this height by adding distilled water or deionized water. 8.6 Place the anode device in the electrolyte solution according to the provisions of 5.2. 915
SY/T 0094-1999
8.7 Connect the positive electrode of the DC power supply to the platinum anode and the negative electrode to the test piece (cathode). Immerse the reference electrode in the electrolyte solution between the platinum anode and the artificial defect hole. The end of the reference electrode is immersed to a depth of 25mm. Adjust the output voltage of the DC power supply so that the potential between the test piece and the saturated copper sulfate reference electrode is -3V.
8.8 During the test, the temperature should be maintained between 21 and 25℃. The test cycle is 90d, and the test cycle can also be 60d or 30d as needed. 8.9 During the test, use a high-resistance multimeter to detect and record the potential value of the test piece relative to the reference electrode and the current value passing through the test piece at least twice a week. After the test, the output voltage of the DC power supply should be adjusted so that the potential between the test piece and the saturated copper sulfate reference electrode is -3V. 8.10 At the end of the test, the test container should be removed immediately, the immersed area should be gently rinsed with warm water, and then the test piece should be wiped dry immediately. Visually check whether there are new leaks in the immersed area of ​​the test piece and the peeling of the anti-corrosion layer around all leaks (including artificial defect holes). Record the condition of the anti-corrosion layer, such as color, bubbling, cracks, attachments, etc. 8.11 Drill a comparison hole in the non-immersed area of ​​the test piece according to the requirements of 8.2. 8.12 Use a sharp knife to make incisions in the center of the artificial defect hole and the comparison hole as shown in Figure 3, and make sure that the anti-corrosion layer is completely cut through to the surface of the steel. 8.13 Use a sharp knife to try to lift the anti-corrosion layer at the comparison hole and the artificial defect hole. With the degree of adhesion of the anti-corrosion layer at the comparison hole as a reference, define the area of ​​the anti-corrosion layer that is easier to lift or peel than the comparison hole as the peeling area.
8.14 Cover the artificial defect hole with translucent coordinate paper to draw the outline of the peeling 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 specimen. The difference between the lifting area and the initial artificial defect area is the peeling area of ​​the specimen. 8.15 Obtain the peeling area of ​​each specimen according to 8.14, and obtain the equivalent circle diameter of the specimen according to formula (1). D=(A/0.785)1/2
Where: A--peeling area of ​​each specimen (mm2); D---equivalent circle diameter of each specimen (mm). 9 Test report
9.1 The complete data of the test piece include:
9.1.1 The name and anti-corrosion grade of the anti-corrosion layer. 9.1.2 The outer diameter, length and wall thickness of the steel pipe. 9.1.3 The source, production date and batch number of the anti-corrosion pipe. 9.1.4
The maximum, minimum and average value of the thickness of the anti-corrosion layer, and the thickness of the anti-corrosion layer at the artificial defect hole. 9.1.5 The diameter and area of ​​the artificial defect hole. 9.2 The data related to the test include:
9.2.1 The start and end date of the test. 9.2.2
The diameter, volume and depth of the electrolyte solution of the test container. 9.2.3 The ratio and pH value of the electrolyte solution. 9.2.4
The detection cycle.
The peeling area and equivalent circle diameter of each test piece. 10 Precision and error
Defect hole cut shape
(1)
Precision
If the test piece is 400 mm long and is taken from the same anti-corrosion pipe, the data obtained by different laboratories should be within ±25% of the average value of the test results.
10.2 Error
If the test pieces are taken from the same anti-corrosion pipe and the test equipment and test methods meet the requirements of this standard, it is not necessary to give the error. 916
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