Surface treatment by brine spray test method
Method of Salt Spray (Fog) Test for Surface Finishing
1. Scope of application: this standard stipulates that the metal substrates shall be sprayed with brine for surface treatment after electroplating, organic or inorganic coating, etc
Test method for corrosion resistance of fog.
2. Test method: this method is to spray the test solution of sodium chloride solution on the electroplating coating in a mist form by using the monitoring water spray testing machine
Corrosion test method for coated films.The main test conditions are shown in table 1.
Table 1 main test conditions
Remark in project preparation test
Concentration of sodium chloride solution (g/l) 50 40~60 * good calibration concentration once a day
PH 6.5 6.5~7.2 pH value in the test was determined after collection
Compressed air pressure (KGF /cm2)......1.00?0.01 continuous without interruption
Spray quantity (ml/80cm2 /h)......1.0~2.0 should be collected for at least 16 hours and averaged
Pressure drum temperature (℃)......47℃
Monitor bucket temperature (℃)......35℃
Laboratory temperature (℃)......35℃ Test at least twice a day, at least 7 hours apart
Laboratory relative humidity...Other humidity requirements above 85% shall be agreed by both parties
The duration of the test shall be the continuous period from the start of the spray to the end, or as agreed by the seller and the buyer.
3. Preparation of test solution: dissolve sodium chloride of test grade (1) in distilled water (or less than 200 PPM in total dissolved solids)
Is mixed into a concentration of 5 1% test fluid (2).After spraying the test liquid at 35℃,
The pH value of the collection solution should be 6.5~7.3 (3).The test fluid cannot contain suspension before spray
Note (1) : sodium chloride must not contain impurities of copper and nickel, and the solid content of sodium iodide must be less than 0.1%.Because in the impure
Corrosion inhibitors may be present, so the total impure content must be less than 0.3%.
(2) : the specific gravity of the test fluid should be 1.0258~1.0402 when measured at 33~35℃, and 1.0258~1.0402 when measured at 25℃
1.0292 ~ 1.0443.The concentration of the test solution can also be determined by silver nitrate solution titration or other methods.
(3) : the pH value of the test solution shall be adjusted by acid monitoring or sodium hydroxide dilute solution and measured by pH meter or other reliable method
Since the water used to prepare the test solution contains carbon dioxide, the solubility of carbon dioxide in the water changes with the temperature and affects the pH value of the solution,
Therefore, the pH value must be carefully controlled.The pH value can be adjusted in either of the following ways:
A. Prepare the test solution at room temperature and spray at 35℃. Part of the solution will escape due to the rising temperature
I'm going to raise the pH.Therefore, when preparing the test liquid at room temperature, the pH value should be adjusted within 6.5, so that it can be closed
The pH value of the collection is between 6.5 and 7.2
B. Before pH value adjustment, make the test solution boil and then cool to 35℃, or maintain the temperature at 35℃ for 48 hours.so
The adjusted pH at 35℃ spray will not change much.
C. Heat the water above 35℃ to remove the dissolved carbon dioxide, and then adjust the test solution and pH value.So in 35 ℃
When spraying, the adjusted pH value does not change much.
(4) : in order to avoid spray nozzle obstruction, the test fluid must be filtered or carefully tilted into the brine barrel, or in front of the spray suction pipe
Install a glass filter or appropriate gauze.
4. Equipment: the equipment required for this test is spray nozzle, brine bucket, test sheet support rack, spray fluid collection container, laboratory (5),
A brine supply tank, a pressure tank, a compressed air supply device and an exhaust device are provided, as shown in figure 1
Test according to the following conditions.
Note (5) : the size of the laboratory must be above 0.48m3.
4.1 the brine spray testing machine and the required pipelines shall be made of pure materials, which shall not affect the corrosion test of the spray or cause corrosion itself
4.2 the spray nozzle shall not directly spray the test liquid to the sample, and the solution gathered at the top of the spray chamber shall not drip onto the test sheet.
4.3 the test fluid dropped from the test sheet shall not be returned to the brine tank and shall be re-used for the test.
4.4 compressed air shall not contain grease and dust, so an air cleaner is required.Air pressure must be maintained at 1.00 0.01 KGF/cm2,
Since compressed air absorbs heat during expansion, preheating (6) is required, as shown in schedule 1, to obtain a uniform temperature spray.
Note (6) : preheat to increase the temperature and humidity of compressed air.
4.5 the horizontal area of the spray catcher is 80cm2 with a diameter of about 10cm, and it is placed near the test piece (near and far from the nozzle)
In two places).
4.6 the spray volume shall be calculated for the whole time. An average of 1.0 to 2.0ml of brine solution shall be collected per hour on the container.spray
The liquid should be collected for at least 16 hours, with the average amount of spray.
4.7 in the brine tank, the concentration of sodium chloride solution should be maintained at 40~60g/l.
4.8 the temperature of the pressure drum shall be maintained at 47?At 1℃, the temperature of brine barrel is 35?1 ℃.
4.9 the relative humidity of the laboratory shall be kept above 85%, and the requirement of higher relative humidity shall be agreed by both parties.
5.1 location: the sample may be taken from the main surface of the product or the product itself as the sample.However, if the product cannot be tested or determined,
A test piece may be substituted by mutual agreement between the parties.The test piece must be representative of the product.
5.2 size: the standard size of the test piece is 150 * 70mm or 100 * 65mm.
5.3 number: the number of samples shall be agreed by the buyer and the seller.
5.4 pre-test treatment
5.4.1 the sample shall be properly cleaned according to the nature and cleanliness of the coating, without abrasions (7) and corrosion or inhibition
Solvent cleaning, and cleaning method should not damage the surface.The stainless steel samples may be used by agreement between the buyer and the seller
Nitric acid cleaning and passivation.After the sample is cleaned (through the water-borne test), dry the water with clean cloth or absorbent paper.
Or dry with dry air without oil.
Note (7) : magnesium oxide paste can be used as a last resort.This paste is 10g trial-grade magnesium oxide added to 100ml distilled water.
5.4.2 unless otherwise specified, the incisions of the sample and the exposed part of the substrate due to hooks, or the defects of the coating due to identification marks,
A suitable protective layer shall be applied during the test.Such as hard wax (ceresin wax), vinyl tape and other insulating materials.
5.4.3 contamination of hand marks will lead to serious poor test results. The samples shall not be contaminated with hand marks after cleaning.
6. Placement of samples: during the test, the position of samples in the laboratory shall meet the following conditions:
6.1 the main surface of the sample shall be inclined from 15 to 30 degrees from the plumb line and shall be parallel to the main flow direction of the spray when viewed from above the laboratory
.When the main surface of a special part with many directions needs to be tested simultaneously, multiple samples may be placed so that each main surface can be accepted simultaneously
6.2 the arrangement of the samples shall make the spray fall freely on all the test pieces, and shall not prevent the free fall of the spray.
6.3 the samples shall not come into contact with each other, nor shall they come into contact with metallic conductors or materials with capillarity, or with anything other than the support frame.
6.4 the brine solution shall not drip from one sample to other samples.
6.5 the sample identification mark or assembly hole shall be covered below.
7. Operation: adjust the temperature of the laboratory and brine tank to 35 ℃, the temperature of the pressure tank to 47 ℃, and maintain the spray pressure
In 1.00 When 0.01kgf/cm2, spray can start.
7.1 test conditions: the test conditions are shown in table 1.
7.2 test time: is the continuous time from the beginning of spray to the end.The test time is an important quality data of the electrodeposit, which is required
The time may be agreed between the buyer and the seller.
7.3 post-test treatment: after the spray test is completed, when opening the upper cover of the laboratory, do not drop the solution and carefully remove the sample, and do not damage the main surface.
As soon as possible, clean water at less than 38℃ to remove the adhering salt particles. Use a brush or sponge to remove the corrosion products beyond the corrosion point, and immediately clean compression
The air is dry.
8. Records: unless otherwise agreed by the parties, the following records shall be kept for this test:
8.1 the quality of the monitoring water used in the preparation of the monitoring water.
8.2 test temperature record.
8.3 the device of the spray catcher shall be recorded daily as follows:
8.3.1 spray amount
8.3.2 collect the specific gravity or concentration of the solution at room temperature.
8.3.3 collect the pH value of the solution.
8.4 type, shape, size and number of samples.
8.5 pre-treatment and post-treatment cleaning of samples.
8.6 method of sample placement in laboratory.
8.7 covering methods as used in section 5.4.2.
8.8 spray time.
8.9 if the test time is interrupted, the reason and time of the interruption shall be recorded.
8.10 all results of other tests.
9. Determination method: the determination of corrosion status of the measured surface can be performed according to the grade number standard diagram shown in FIG. 2 to FIG. 13.Blister, crack
Marks that are difficult to determine using standard charts may be determined by a magnifying glass with a ruler, or by a method agreed between the buyer and the seller in advance.