Test procedure for salt spray test chamber

The salt spray test chamber uses salt spray corrosion to detect the corrosion resistance of the tested samples. The salt spray is a dispersion system consisting of tiny droplets of salt in the atmosphere. It is a series of artificial environment three-proof series. One type, many enterprise products need to simulate the damage caused by the surrounding climate of the ocean, so the salt spray test box should be shipped. Today we will have an in-depth understanding of the salt spray test chamber!

Principle of Salt Spray Corrosion

The corrosion of the metal material by the salt spray is mainly caused by the electrochemical reaction of the conductive salt solution into the metal, forming a "low potential metal-electrolyte solution-high potential impurity" micro-battery system, electron transfer occurs, and the metal as the anode is dissolved. A new compound, the corrosive, is formed. Similarly, when the metal protective layer and the organic material protective layer are infiltrated into the inside, a microbattery in which a metal is used as an electrode and a metal protective layer or an organic material is used as another electrode is formed.

The main role of salt spray corrosion damage is chloride ion. It has a strong penetrating power and easily penetrates the metal oxide layer into the metal interior, destroying the passive state of the metal. At the same time, the chloride ion has a small hydration energy and is easily adsorbed on the metal surface instead of protecting the oxygen in the oxide layer of the metal to damage the metal.

In addition to chloride ions, the salt spray corrosion mechanism is also affected by oxygen dissolved in the salt solution (essentially the salt liquid film dissolved on the surface of the sample). Oxygen can cause the depolarization process of the metal surface, accelerate the dissolution of the anode metal, and continuously deposit on the surface of the sample due to continuous spraying during the salt spray test, so that the oxygen content is kept close to saturation. The formation of the corrosion product expands the volume of the salt solution that penetrates into the metal defect, thereby increasing the internal stress of the metal, causing stress corrosion, causing the protective layer to bulge.

Ready to Work

1. Distilled water or deionized water can be added to the stainless steel barrel. Open the gas valve and the saturator water supply valve before adding water. It is advisable to add the water level to the 4/5 position of the water level glass box. When adding to the appropriate water level, it should be close the bleed valve and close the water supply valve of the saturator. Due to long-term tests, the water in the saturator will evaporate and consume. When the water level is reduced to 2/5, the saturated barrel should be replenished in time to prevent dry burning inside the heating tube due to lack of water, and the saturator and internal heating elements are baked.

2. The water seal groove around the upper part of the tank should be filled with distilled water or deionized water. When the lid is closed, the water and salt spray are not spilled.

3. Check whether the water pipe between the storage tank and the sprayer in the working room is well connected, and add the prepared salt solution (generally prepared at a concentration of 5%) into the storage tank. Add distilled water or deionized water to the bottom of the heating tank of the studio to prevent the box from cracking and aging during heating.

Method of Operation

1. Please connect the power cord first, connect the air pressure tube, then open the lid and pour pure water or distilled water into the water tank at the bottom of the tank until the low water level on the panel is off, otherwise it will not be normal. work.

2. The drain pipe and the exhaust pipe in the salt spray fog corrosion testing equipment need to be connected. After the completion, the water tank will be added to the water tank to avoid the leakage of salt spray.

3. When everything is ready, you can press the power switch to turn on the power, then press the operation switch to set the temperature of the test box and the temperature of the saturator. The setting method is as long as the two on the control panel. Each CNC instrument dials the gear to the set gear, sets the required temperature value, and then dials the gear to the measurement file. Under normal circumstances, the test temperature should be set to 35 °C, and the saturator temperature is set to 35. °C to 40 °C.

4. The control value of the over-temperature protector on the right side of the salt spray test box is generally set at 55 °C to prevent the temperature control instrument from malfunctioning and burning the box. When the temperature in the working room exceeds 55 °C, the over-temperature protection will automatically cut off the total power supply. Users should not arbitrarily adjust the protector.

5. Pour the prepared brine into a salt water tank, add water to the wet bulb, cover the gauze with a wet bulb thermometer, and place the end of the gauze in the wet bulb.

6. Place the sample on the rack and set the angle required by the experiment. Set the parameters related to the test by the control meter, then press the power and operation keys to start the test.

Precautions

1. The salt spray test chamber and its required piping shall be made of blunt materials, which shall not affect the corrosion test of the spray or be corroded by itself.

2. The test solution dropped from the test piece shall not flow back to the salt water tank and be used for the test.

3. The spray nozzle can't directly spray the test liquid to the sample, and the solution gathered at the top of the salt spray chamber should not drip on the test piece.

4. The spray taker has a horizontal take-up area of 80 cm2 and a diameter of about 10 cm, placed near the test piece (near the nearest and farthest point of the nozzle).

5. Compressed air should not contain grease and dust, so air purifier must be provided. The air pressure must be kept at 1.00±0.01kgf/cm2. Because compressed air has heat absorption when it expands, it must be preheated to increase compression. The temperature and humidity of the air, as shown in Schedule 2, to obtain a uniform temperature spray.

6. The amount of spray liquid in the salt spray test chamber is calculated over the whole time. On the container, an average of 1.0 to 2.0 ml of saline solution should be collected per hour. The spray liquid should be collected for at least 16 hours, and the average value is not sprayed.

7. The temperature of the pressure tank should be kept at 47±1°C, and the temperature of the salt water tank should be 35±1°C.

8. In the test salt water tank, the concentration of sodium chloride solution should be maintained at 40~60g/L. When the test salt liquid is not used up within 1 week, it needs to be replaced. If the test time exceeds 1 week, the test should be carried out. Indoor cleaning, the test salt liquid, the water in the heating tank is discharged.

9. In the experimental work, when there is experimental mist leakage at the edge of the experiment cover, water should be added to the sealed water tank. If the test period is more than 1 month, the water in the hot water tank should be replaced.

10. The relative humidity of the salt spray test chamber must be maintained above 85%. The higher relative humidity requirements can be determined by agreement with the customer.

The Difference and Connection Between the Salt Spray Machine and the Natural Environment Exposure in the Test:

The salt spray test is an environmental test that uses the artificial simulated salt spray environmental conditions created by the salt spray test equipment to evaluate the corrosion resistance of products or metal materials. It is divided into natural environmental exposure test and artificial accelerated simulated salt spray environmental test. The artificial simulated salt spray environment test uses an artificial method in the volume space of the salt spray test chamber to cause a salt spray environment to evaluate the salt spray corrosion resistance quality of the product.

The salt concentration of the chloride in the artificial salt spray environment is several times or several times that of the salt spray content of the general natural environment. If a product sample is tested, it may take 1 year of corrosion time under natural environment exposure, and only 24 hours under artificial simulated salt spray environment.

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