Salt spray test national standards

1. Application scope of salt spray test:
This standard specifies the salt spray corrosion resistance test methods for various surface treatments of various metal substrates after plating, organic or inorganic coating.

2. Salt spray test method:
This method is a corrosion test method in which a test solution of a sodium chloride solution is sprayed on a plating film by using a salt spray tester. The main conditions of the test are shown in Table 1.
Table 1 The main test conditions During the preparation of the project Remarks Concentration of sodium chloride solution in the test (g/l) 50 40~60 It is best to calibrate the concentration once a day. pH 6.5 6.5~7.2 After collection, determine the pH value of the test Compressed air pressure (kgf /cm2) ...... 1.00kgf/cm2 0.01 No interruption of continuous spray volume (ml/80cm2/h) ...... 1.0~2.0ml Should be collected for at least 16 hours to find the average pressure barrel temperature (°C) ...... 47°C±1 °C
Water barrel temperature (°C) ...... 35°C±1°C
Test chamber temperature (°C) ...... 35°C±1°C At least twice a day, at least 7 hours apart, Relative humidity of the chamber... 85% or more Other humidity requirements Test time agreed by the buyer and the seller: From the start of spraying to the end The continuous time, or agreement between the buyer and the seller.

3. Preparation of test solution for salt spray test: Dissolve reagent grade sodium chloride
(1) In distilled water (or water with total dissolved solids less than 200 ppm), prepare a test solution with a concentration of 5%
(2) After the test solution is sprayed at 35°C, the pH of the collected solution should be 6.5~7.3.
(3) Before spraying, this test solution must not contain suspended solids.
Note (1): Sodium chloride cannot contain impurities of copper and nickel. The content of sodium iodide in the solid must be less than 0.1%. Since the impurities may contain corrosion inhibitors, the total impurity content must be less than 0.3%.
(2) : The specific gravity of the test solution should be measured at 33-35°C and it should be 1.0258-1.0402. The specific gravity at 25°C should be 1.0292-1.0443. The concentration of this test solution can also be calibrated using silver nitrate solution titration or other methods.
(3) : The test solution shall be adjusted to the pH of the test drug's acid or sodium hydroxide dilute solution and measured by a pH meter or other reliable method. The water contained in the test solution contains carbon dioxide, and the solubility of carbon dioxide in water changes with temperature. Since the pH of the solution is affected, the pH must be carefully controlled.
The pH can be adjusted by any of the following methods:
a. Prepare the test solution at room temperature and spray at 35°C. As the temperature increases, some of the carbon dioxide escapes the solution and raises the pH. Therefore, when the test solution is prepared at room temperature, the pH should be adjusted within 6.5 so that the pH of the collected solution can be between 6.5 and 7.2.
b. Before pH adjustment, allow the test solution to be boiled and then cooled to 35°C or maintained at 35°C for 48 hours. When the pH adjusted in this way was sprayed at 35°C, there would not be much change.
c. Heat the water above 35°C to remove the dissolved carbon dioxide, then prepare the test solution and adjust the pH. When sprayed at 35[deg.] C. in this way, the adjusted pH does not change too much.
(4) : To avoid clogging of the spray nozzle, the test liquid must be filtered or carefully poured into a saline tank, or a glass filter or a suitable gauze should be fitted to the front of the spray hose.

4. Salt spray test equipment:
The equipment required for this test consists of a spray nozzle, a brine tank, a test piece support frame, a spray liquid collection container, a test chamber (5), a salt water supply barrel, a pressure tank, compressed air supply equipment, and an exhaust device, and Test according to the following conditions.
Remarks (5): The size of the laboratory must be 0.48m3 or more.

4.1 The saline spray tester and its required piping should be made of pure material, which cannot affect the corrosion test of the spray or itself.
4.2 The spray nozzle shall not spray the test solution directly onto the sample. The solution collected on the top of the spray chamber shall not drip on the test piece.
4.3 The test solution dropped by the test piece shall not be returned to the saline tank for reuse in the test.
4.4 The compressed air must not contain grease and dust, so an air cleaner is required. The air pressure must be maintained at 1.00?0.01kgf/cm2. Since the compressed air has an endothermic phenomenon when it is inflated, it must be warmed up in advance (6), as shown in Exhibit 1, in order to obtain a uniform spray temperature.
Note (6): Preheat to increase the temperature and humidity of the compressed air.

4.5 The sprayer has a horizontal area of ​​80 cm2 and a diameter of about 10 cm and is placed near the test piece (near the closest and farthest points to the nozzle).
4.6 The amount of spray solution is calculated over the entire time. On the container, an average of 1.0 to 2.0 ml of saline solution can be collected per hour. The spray solution should be collected for at least 16 hours and the average value should be expressed as the spray volume.
4.7 For the test bucket, the concentration of sodium chloride solution should be maintained at 40-60g/l.
4.8 The temperature of the pressure tank shall be maintained at 47 to 1°C, and the temperature of the saline tank shall be 35 to 1°C.
4.9 The relative humidity of the laboratory must be kept above 85%. The higher relative humidity requirement can be agreed by the buyer and the seller.

5. Salt spray test specimen:
5.1 Location: Samples may be taken from the main surface of the product or the product itself as a sample. However, if it cannot be tested or determined by the product, the parties can agree to replace the test piece. This test piece must be representative of the product.
5.2 Scale: The standard size of the test piece is 150*70mm, or 100*65mm.
5.3 Number: The number of specimens is agreed by the buyer and the seller.

5.4 Pre-test treatment
5.4.1 The sample shall be properly cleaned in accordance with the nature of the coating and the degree of cleanliness. It shall not be cleaned with abrasives (7) and solvents with a corrosive or inhibitory effect, and the cleaning method shall not damage the surface. As for the stainless steel samples, the agreement between buyers and sellers for nitric acid cleaning and passivation can be used. After cleaning the sample (by dialing the water test), dry the water with a clean cloth or blotting paper.
Or blow dry with oil-free dry air.
Note (7) : Magnesium oxide paste may be used as a last resort. The paste was 10 g of reagent grade magnesium oxide added to 100 ml of distilled water.

5.4.2 Unless otherwise specified, otherwise the specimen is notched and the exposed part of the substrate is caused by hooking, or the plating defect is caused by the identification mark.
The test should be covered with a suitable protective layer. Such as hard wax (ceresin wax), vinyl tape and other insulation.
5.4.3 Handprint contamination can cause serious adverse test results. The sample must not have any handprint contamination after cleansing.

6. Place salt spray test specimens:
During the test, the location of the test specimen within the test chamber must meet the following conditions:
6.1 The main surface of the specimen is inclined 15 to 30 degrees from the plumb line, and it should be parallel to the main flow direction of the spray when viewed from above the test chamber. When a particular part has major surfaces with many directions that need to be tested at the same time, it may be desirable to place multiple specimens so that each major surface can be subjected to simultaneous water spray.
6.2 The arrangement of the samples should be such that the spray falls freely on all test strips and should not interfere with the free fall of the spray.
6.3 The specimens shall not be in contact with each other, nor may they come in contact with metallic conductors or substances that are subject to capillary action, as well as anything other than support frames.
6.4 The saline solution shall not drip from one sample to the other.
6.5 Sample identification mark or assembly hole should be covered below.

7. Salt spray test operation:
The temperature of the test chamber and brine tank was adjusted to 35 degrees Celsius, the pressure tank temperature was 47 degrees Celsius, and spray pressure was maintained at 1.00 kgf 0.01 kgf/cm2.
7.1 Test conditions: The test conditions are shown in Table 1.
7.2 Test time: It is the continuous time from the start of spraying to the end. The test time is an important quality data of the electroplating layer, and the required time can be agreed by the buyer and the seller.
7.3 Post-test treatment: After the spray test is completed, when the lid of the test chamber is opened, the sample shall be carefully removed without dropping the solution. The main surface shall not be damaged. The adhered salt particles shall be washed away with clean water at a temperature below 38°C as soon as possible. Or sponge to remove corrosion products other than corrosion, and immediately dry it with clean compressed air.

8. Salt spray test record:
If the buyer and the seller do not agree otherwise, this test shall have the following records: (Annex 2 is a reference record sheet)

8.1 The quality of monitoring and water used when preparing water supervision.
8.2 Test temperature records.
8.3 sprayer device should be recorded daily as follows:
8.3.1 Spray volume 8.3.2 Collect the specific gravity or concentration of the solution at room temperature.
8.3.3 Collect the pH of the solution.
8.4 Types, shapes, dimensions, and numbers of specimens.
8.5 Pre-treatment cleaning of samples and post-treatment cleaning methods.
8.6 Placement of the sample in the test chamber.
8.7 Coverage methods used in Section 5.4.2.
8.8 Spray time.
8.9 If the test time is interrupted, the cause and time of the interruption must be recorded.
8.10 All the results of other inspections.

9. Determination method:
The determination of the surface corrosion condition can be performed in accordance with the level number standard chart shown in FIGS. 2 to 13 . Blisters, cracks, etc., which are difficult to determine using a standard chart, may be judged by a magnifying glass with a ruler, or determined by the buyer and seller in advance.

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