1. Subject content and applicable scope
This standard provides a method for determining the resistance of coatings to neutral salt spray.
The methods specified in this standard may be used as a means of testing the quality of brush or paint systems.
2 reference standard
GB 1266 sodium oxide
GB 1764 method for determination of paint film thickness
GB 1765 method for determination of temperature and heat resistance, salt spray resistance and weather resistance (artificial acceleration) by flow rate membrane method
Sampling of GB 3186 coating products
GB 6682 laboratory water specifications
GB 9271 standard test board for paints and varnishes
GB 9278 coating sample condition adjustment and test temperature and humidity
GB 9286 color bar and clean paint film grid test
3 test solution
3. 1 test ficus solution is prepared by dissolving the pure uranium chloride conforming to GB 1266 in the third-grade water conforming to GB 6682, and its concentration is 50:!:
10 g/L ll.
3.2 the pH value of the test solution (3.1) shall be determined at 25 0C with a pH meter (precision 0.1 pH) to be 6.5 ~ 7.2.When out of range, pure hydrochloric acid or sodium hydroxide solution can be added to adjust.Precision test paper calibrated by pH meter can be used for routine inspection.
3.3 the storage tank of the test solution injection equipment shall be filtered before it is used to prevent solid substances from blocking the nozzle.
The equipment is a salt spray test box and shall include the following components.
4.1 spray chamber: it is made of or lined with materials resistant to corrosion of banyan in salt water. The top cover or cover shall be tilted upward and the included Angle with the horizontal plane shall be greater than
25 0, so that the liquid droplets agglutinated on the lid do not drip onto the test plate.
4.1.1 the size and shape of the spray chamber shall ensure that the amount of solution collected in the chamber reaches the specified range of 8.2.
In order to ensure the uniformity of the spray, the volume of the spray chamber shall not be less than 0.4m 3. For the spray chamber with A volume of more than 2 meters, careful consideration shall be given in the design and construction for the convenience of operation. The factors to be considered are listed in appendix A.
4.1.2 the constant temperature control element z is located in the spray room, at least 100 mm away from the wall of the box, or in the indoor water jacket, and can make all parts of the spray room reach the specified temperature.
The thermometer is located in the room more than 100 mm from the wall of the box, and can read out of the box.
4.1.3 nozzle: made of inert material resistant to salt water corrosion, such as glass or plastic.Use adjustable baffles to prevent direct salt spray impact test
Board to help evenly distribute indoor spray.
4.1.4 salt spray collector: a flying collector made of glass or other chemically inert material shall have at least two places where test plates are placed in the spray chamber as prepared by ZU.One is placed near the entrance to the spray, the other far from the entrance to the spray, and the position requires that only the salt spray is collected, not the liquid dripping from the sample or other parts of the room.
Note :1) the tube of glass funnel can be inserted into the graduated measuring cylinder.The diameter of the funnel is 100 mm and its collection area is 80 cm 2.
2) if two or more nozzles are used, the number of collectors is at least twice the number of nozzles.
4.1.5 test solution storage tank: made of materials resistant to salt water solution corrosion and equipped with devices to maintain a constant water level in the tank.
4.2 clean air feeder: the compressed air supplied for spray shall be filtered to remove oil and solid particles.Before entering the nozzle, the air should pass through a saturated tank with GB 6682 water whose temperature is several degrees higher than that of the spray chamber to humidify the air and prevent the gasification of the test solution.The temperature of the water depends on the air pressure used and the type of nozzle. The air pressure is adjusted so that the collecting speed and concentration in the tank are kept in the gauge
Within a certain range.(see 8.2)
Spray pressure is maintained at 70~170 kPa.
Note: to prevent pressure formation in the spray room, air from the device is usually discharged into the atmosphere outside the laboratory.
4.3 test solution storage tank: made of material resistant to saline solution.
Samples are selected according to GB 3186.
6. Test sample
6.1 materials and dimensions
Unless otherwise specified or agreed by the parties concerned, the test board shall be of polished copper sheet 100 mm x 150 mm as required by GB 9271.
If no scratches are required, 70 mm x 150 mm test board II can also be used.
6.2 plate making and coating
Unless otherwise specified, test plates shall be prepared in accordance with GB 1765.The dry film thickness was measured by GB 1764 non-destructive method.
The back and periphery of the test board shall be coated with the tested product or coating system.If the tested product is not used for coating, the tested product is required
More corrosion resistant products to be coated.
6.3 drying and condition adjustment
The coated test board shall be dried in accordance with the standard time and conditions.Unless otherwise provided, the temperature shall be 23 sh 2"C and the relative humidity (50 soil 5)%
With air circulation and no direct exposure to sunlight, the condition shall be adjusted for at least 16 hours and then put into test as soon as possible.
6.4 preparation of scratches
If scratches are required, they should be scratched through the coating to the substrate.And make the scratch more than 20 mm from any edge of the test plate.Unless otherwise specified, it shall be used
Single blade cutter recommended in GB 9286.
7. Method of exposure of test board
7.1 the test plate should not be placed on the straight track of the mist particles coming out of the nozzle, and the baffle can be used to prevent the spray from directly hitting the test plate.
Adoption note 2
1] ISO specifies 150 mmX 100 mm.
7.2 the exposure Angle of the test board in the box is very important. The subject surface of each test board is upward and the included Angle with the vertical line is 20.Soil 50.
Note z when testing painted parts of different shapes, the method of exposure shall be agreed upon by the parties concerned.In the case of such tests, it is particularly important that these differences be made
Shape parts are placed in their normal state of use.Under this requirement, the parts should be placed as far as possible to avoid obstructing the flow of air.If the parts get in the way
With the flow of air, other test plates and components cannot be tested at the same time.
It should be noted that the degree of damage to the coating of the test plate varies with the position of placement, and due consideration should be given to this.
7.3 the test plates shall be arranged so that they do not touch each other or the box body.The surface of the subject should be exposed to an area where salt spray settles unimpeded.Test plate
Place it on the same level in the box to prevent droplets from falling from the upper test board or bracket onto the other test board below.
Note s is to periodically change the position of the test board.If the position is changed during the inspection period, the mode of transposition shall be indicated in the test report.
7.4 the support of the test board must be made of an inert nonmetallic material such as glass, plastic or painted wood.If the test board needs to be hung, then hang the appliance
Made of synthetic fiber, cotton thread or other inert insulating material.
8 operating conditions
8.1 the temperature in the spray chamber shall be 35 earth 2"C.
8.2 the solution collected in each collector (4.1.4) is chlorinated at a concentration of 50 g/L(3.1) and a pH value of 6.5 to 7.2 (3.2).
After a minimum period of 24 h, the solution collected by each collector was calculated. The area of every 80 cm2 should be 1~2 mL/h.
8.3 the test solution that has been sprayed cannot be reused.
8.4 if the equipment has been tested in a manner different from that prescribed in this test, it must be thoroughly cleaned before the test.
9 test steps
9.1 debugging shall be conducted in accordance with the conditions specified in chapter 8.
9.2 according to the provisions of chapter 7, the test plate (or part) shall be discharged in the spray chamber.
9.3 close the top cover of the fog chamber, open the test solution storage tank valve, and make the solution flow to the storage tank for the test.Spray continuously throughout the test cycle.
9.4 except for inspection, rearrangement or taking out the test board;Check and replenish the solution in the storage tank;Or make necessary records in accordance with chapter 8 before stopping the spray.
9.5 unless otherwise provided, two parallel assays shall be made.
Inspection of test board
The test plate shall be inspected by visual inspection periodically, but the surface of the test plate shall not be damaged.The inspection time for any 24 h cycle should not exceed
60 min, and whenever possible at the same time every day.The test plate should not be dry.
At the end of the specified test period, remove the test board from the box and rinse the test board with clean water to remove the test solution remaining on the surface.
Immediately check the surface of the test plate for signs of damage, such as blistering, rust, reduced adhesion, corrosion spread from scratch.
If required, place the test plate in a standard environment conforming to GB 9278 and adjust the state to the specified time, and then check the surface of the test plate
If damage to the substrate needs to be examined, the coating shall be removed as agreed.
11 test report
The test report shall include at least the following contents z
A. Model and name of the tested product;
B. Indicate the adoption of national standards;
C. Test duration;
D. transposition mode of test board (7.3 note h
E. Test results;
The design and structure of the spray chamber with a volume larger than 2 m3 should be considered
The number and position of A1 nozzles and baffles shall ensure even spray, and the collection volume shall meet the range specified in 8.2.
A2 the number of collectors should meet the requirements of 4.1.4 and be able to monitor the spray status.
A3 heating, insulation and other temperature control methods should ensure that all test plates in the spray chamber have uniform temperature distribution at all positions.
A4 if the size of spray room is not allowed to meet the requirements of 4.1, so that the included Angle between the top cover and the horizontal plane is more than 25.Corner, top cover design (such as auxiliary top cover >