The compound salt spray test chamber is mainly used for auto parts, aviation equipment, photographic devices, building materials, electroformed coatings, electronic motor systems, and other metals under harsh environmental changes in electrochemical corrosion resistance.
According to the survey, the corrosion of metal materials mostly occurs in the atmosphere. The atmosphere contains oxygen, humidity, temperature changes, pollutants, and other corrosive components and corrosion factors. However, the corrosion of metal salts by salt spray is mainly due to the electrochemical reaction of the conductive salt solution entering the metal. Thus, a micro-battery system of “low potential metal electrolyte solution – high potential impurity” is formed. Finally, electron transfer occurs and the metal dissolves as an anode.
In fact, the main action of the composite salt spray corrosion process is chloride ions. Because it has a strong penetrating force, it is easy to penetrate the metal oxide layer into the metal and destroy the passivation state of the metal. At the same time, the hydration energy of chlorine is low. It is easily adsorbed on the metal surface and replaces oxygen in the oxide layer. To protect the metal from damage.
Moreover, the compound salt spray test chamber has the functions of the basic composite salt spray test chamber. Combined with the function of alternating cycle salt spray test, it can provide a test environment such as forced corrosion and filamentary corrosion. Such as hot air drying, hot wet drying, and forced drying.
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It doesn’t take much evidence to understand how corrosion can negatively impact our lives. And it goes beyond the outdated view of rust.
In general, climate drivers are well aware of the importance of corrosion-resistant materials. Salt buildup on winter roads wreaks havoc on the landing gear of cars, especially those known as “eggbeaters” or “clunky” cars. Ultimately, corrosion poses a threat to the safety of drivers and everyone else on the road.
Additionally, just as automobile companies focus part of their research efforts on the development of corrosion-resistant components. Municipalities are also looking at the roads themselves. In fact, the combination of salt and water corrodes asphalt and concrete, and sometimes just below the surface.
Potholes followed. It is understood that the researchers are working to solve this problem by developing water-resistant and salt-resistant pavement solutions.
There is also a very real public health problem. A 2019 report by the National Society of Corrosion Engineers estimated that the direct cost of corrosion of drinking water and sewer systems in the United States is $80 billion. If this problem is not addressed, contaminated water will pose a threat to citizens across the country.
- Equipped with a spray adjuster for easy adjustment of spray density.
- A heater is installed at the bottom of the test chamber to heat the water and maintain the temperature.
- Equipped with a sealed sink to avoid spray leakage, the principle of water sealing is adopted.
- The inner shell of the salt spray test chamber is made of PVC material, which effectively prevents corrosion.
- The test cover is clear and easier to observe the test conditions.
- Low load thresholds for loading and unloading.
- Large capacity floor-standing salt solution reservoir.
- Calibration certificate.
- Canopy color selection.
- One set of sample holders.
- Interior picture windows.
- Consumable spare parts kit.
- Easy-to-access salt mist nebulizer made of transparent, wear-resistant acrylic.
- Purges the cabinet interior with fresh air after testing and before opening the chamber.
- Additional features for a premium salt spray chamber:
- Touch screen, full-color user control interface, the latest version of our highly intuitive operating software, easy to program and use.
- The operating software has a very large capacity and can be used to create complex multi-step test programs, so it can accommodate the widest possible test profile.
- The icon-based control interface provides several built-in languages for ease of understanding and use.
Although it is called salt spray test and salt spray test chamber, the name is somewhat misleading. Because the spray usually comes in the form of fog or ultra-fine fog. This creates an environment that accelerates corrosion. In fact, this condition can also be isolated by controlling the ambient temperature at 95°F(35°C) and PH.
Salt spray testing is used to determine the corrosion resistance of a material. These typically include the following:
- Phosphating the surface followed by paint, primer, varnish, or anti-rust treatment
- Galvanized and zinc alloys
- Electroplated chrome, nickel, copper, and tin
- Coatings that are not electrolyzed, such as zinc sheet coatings
- Organic coatings
- Paints and coatings
Here are the installation steps for the compound salt spray test chamber.
1) Open the packaging of the compound salt spray test chamber
- Be careful when opening the package. While the transparent sheets used in the compound salt spray chambers, which are usually made of fluorite, are fairly durable, the transport may be rough enough to cause damage. Be sure to check the salt spray chamber for cracks that may occur during transportation.
- If you notice cracks or debris in fluorite, contact your manufacturer immediately. Just like a car windshield, cracks widen over time.
- Find a hard, flat surface with plenty of ventilation to be a resting place for the salt spray chamber.
- You want to have plenty of space around the room in a well-ventilated room. (See below for more information on ventilation.)
2) Electricity and utility requirements
Electrical panels and chambers are fully wired and ready for use. Keep in mind that in most cases, the power supply must be grounded.
You also need a reliable source of water. It is worth noting that the salt spray chamber requires distilled (demonstrated) water. Before putting untreated tap water into the chamber, you always want to feed it through a desalination filter.
Although the amount of water consumed in the tank varies by model. But here’s a little formula to help determine the capacity of the desalination cylinder:1600 TDS / 17.12 ppm = capacity (gallons). When three-quarters of the particle has turned into the color it used, you should replace the cartridge.
3) Salt spray nozzle assembly
The compound salt spray chamber is equipped with atomizing nozzle. But if you need to replace it, you may need to do the following:
- Apply a quarter-inch-wide Teflon tape strip to all joints. Avoid letting the tape get inside the pipe.
- It is best to place the tape at least two to three lines from the end of the pipe.
- While preventing any foreign objects from entering the pipe, screw the acrylic quarter-inch fitting into the tape hole inside the chamber. You should be able to easily tighten it by hand.
- After tightening by hand, adjust the nozzle so that the spray faces the front of the chamber, while another tape hole in the nozzle points downwards.
- Tighten the long acrylic quarter-inch threaded tube into the tape hole at the bottom of the nozzle until it fits snugly. (This tube is called a siphon tube.)
- Place the nylon mesh filter on the other end of the siphon and secure it in place with a rubber band. If using a special MIL-STD-202 or MIL-STD-810 filter, connect it to the end of the siphon.
- Place the lid of the salt bank on top of the salt bank and you are done.
4) Salt spray chamber ventilation
What’s more, in order to prevent back pressure in the chamber, you have to exhaust it. When setting up the chamber, you are sure to install a non-corrosive three-inch pipe from the exhaust chamber to a point outside the building. The exhaust port should be short and straight. And gently slope down from the chamber to avoid any liquid traps. Finally, it should be shielded from wind or airflow.
What you need to know is that while flexible hoses are an option, you must ensure that the hose does not sag. If it sags, it creates a liquid trap. If your exhaust pipe is longer than 10 feet, a two-inch line should be used. If your pipe must exit from the roof up, use a T-joint instead of a bend. Adjust T so that an 18-inch drop line and drain can be added. Finally, ensure that the exhaust line is always clear.
5) Salt chamber for gas supply
Moreover, Compound salt spray chambers require clean, oil-free compressed air. A valve marked “air” is also installed at the rear end of the composite salt spray chamber. Compressed air flow SCFM typically ranges from 1.5/0.71 (l/s) to 4.0/1.89. The pressure of the PSIG will run between 6-10, depending on the model.
First, here are some things to know about the construction of a typical compound salt spray chamber.
Test chamber structure
- The compound salt spray chamber uses a double-walled structure that provides warm air circulation between the inner and outer walls. The blower and heater located in the base circulate hot air in a closed loop.
- The thermostat is located in the test area of the chamber and is factory set to keep the temperature at plus or minus 95 degrees Fahrenheit.
- The salt atmosphere is created through a nebulization nozzle, which uses compressed air to siphon the salt solution from the tank. Compressed air is first heated and saturated by bubbling hot water stored in a saturation tower.
- By saturating the air at temperatures higher than the air temperature near the salt spray nozzle, a small amount of condensed moisture constantly purges the nozzle, reducing the tendency of salt solution crystallization and blockage. This ensures consistent conditions of the nozzles, providing a uniform atmosphere in the test chamber.
- The salt solution should be prepared according to any test specifications you are trying to meet. Many standards require a 20% saline solution, which means that each gallon of distilled or desalinated water contains two pounds of sodium chloride per ounce.
- The thermostat located in the chamber test area controls the internal temperature, keeping it at plus or minus 2 degrees Fahrenheit (35 degrees Celsius). The thermostat also controls the air heater mounted on the blower. This thermostat is factory-set and should not be adjusted in any way.
- If you need to change the temperature, you can modify the thermostat by turning the adjustment screw. The screw rotates clockwise to reduce the temperature. Before making other adjustments, be sure to allow enough time for stabilization.
You should follow the following sequence of actions at the beginning of each test:
1. Make sure the chamber is on a horizontal surface.
2. Connect the ventilation ducts to make sure they are not restricted.
3. Fill the tower reservoir.
4. Fill the salt tank to within one inch of the top and replace the lid.
- When filling the reservoir, the temperature of the solution should be 95 degrees Fahrenheit or less.
5. Fill the top cover groove and close.
- The top cover of the chamber has a water seal to prevent salt spray from entering the room.
- Fill the tank regularly with distilled or desalinated water.
- It is important that the chamber is properly leveled to provide a satisfactory seal.
6. Connect the chamber’s compressed air supply.
- Now it is suitable for you to double-check that the air is supplied at the correct pressure.
7. Open the chamber air valve.
8. Turn on the compressed air supply.
9. Select the valve in the salt spray position and place the tower switch in the open position.
1) Other notes
10. Place the circulation switch and chamber switch in the open position and check the following:
- Air should bubble through the saturation tower.
- The atomization nozzle should produce fine fog.
- Air flowing through the exhaust line is required for better ventilation of the machine.
- There should not be any air bubbling through the water seal around the lid.
11. After the chamber temperature is stable (about 30 minutes after the chamber indicator first starts to cycle on and off), check the chamber and tower temperature.
- Observe the temperature of all heating zones to ensure that the maximum temperature specified in the manual is not exceeded.
- Check the correct operation of the thermostat by observing the electrical panel indicator.
- These lights should cycle when various temperatures approach their set value.
12. Check the normal operation of the salt spray nozzle.
13. The chamber is now ready for use!
- At the end of the test, place the start switch in the purge position. Ensure that air enters the chamber directly and flows freely from the exhaust pipe. This is roughly all you need to know when installing, setting up, and operating a new salt spray chamber.
In fact, the critical relative humidity for metal corrosion is about 70%. When the relative humidity reaches or exceeds this critical humidity, the salt dissolves to form an electrolyte with good electrical conductivity.
Conversely, when the relative humidity decreases, the salt solution concentration increases. Until the crystallization salt is out, the corrosion rate decreases accordingly. When the temperature increases, the molecular movement intensifies and the salt spray corrosion rate is high.
The International Electrotechnical Commission pointed out that for every 10℃ increase in temperature, the corrosion rate is increased by 2 to 3 times, and the electrical conductivity of the electrolyte is increased by 10 to 20%. Therefore, for the neutral salt spray test, it is generally considered appropriate to choose a test temperature of 35℃.
When the concentration is less than 5%, the corrosion rate of steel, nickel, and brass increases with the increase of the concentration. On the other hand, when the concentration exceeds 5%, the corrosion rate of these metals decreases with the increase in the concentration.
This is because, in the low concentration range, the oxygen content increases with the salt concentration; When the salt concentration is increased to 5%. The oxygen content reaches relative saturation, and if the salt concentration continues to increase, the oxygen content decreases accordingly.
With the decrease in oxygen content, the depolarization ability of oxygen also decreases, that is, the corrosion effect is weakened. In short, for zinc, cadmium, copper, and other metals, the corrosion rate always increases with the increase of the concentration of the salt solution.
According to the observation, the salt spray sedimentation direction is close to the vertical direction. When the sample is placed horizontally, its projected area is the largest, and the sample surface is most affected by the salt spray, so the corrosion is the most severe.
The results show that when the steel plate is at a 45-degree Angle to the horizontal line, the weight loss is 250g per square meter. When the plane of the steel plate is parallel to the vertical line, the weight loss of corrosion is 140 grams per square meter. The GB/T 2423.17-93 standard stipulates that flat samples should be placed vertically at a 30-degree Angle.
Therefore, when we use the composite salt spray test chamber at the end of each test or test, the solution of the measuring cup should be emptied and washed in time. To avoid the salt solution crystallization accumulation, affect the settlement calculation.
When the machine is not used for a long time, you should drain the water in the saturated tank. During normal use, the water in the saturator should also be replaced normally within a certain period of time. When restarting the test, you should check all electrical systems.
1) Environmental requirements during use, salt spray test cases
- The distance between the laboratory and the laboratory should be more than sixty centimeters.
- The ambient temperature of the equipment should be kept stable between fifteen and thirty degrees Celsius.
- Do not expose to sunlight or other strong light sources.
- Avoid strong airflow. If it cannot be completely avoided, there should be no airflow directly to the box.
- High concentrations of dust and corrosive substances are not allowed to enter the environment.
- Voltage fluctuations are less than or equal to plus or minus 10%.
- Air compressors for regular lubrication of test chambers.
2) When not in use for a long time, restart the machine for testing and check all electrical systems first
When you do not use the machine for a long time, you should restart the machine for testing. And check all electrical systems to ensure your safety.
3) Other precautions:
- Use only parts from the manufacturer of the specific chamber.
- Always connect the chamber to a grounded power source.
- Always disconnect the chamber from all power sources before repairing it.
- Do not expose the chamber to high concentrations of solvent. This can lead to cracking of the fluorite wall.
- Do not dissolve salt in a salt bank tank with hot water. This can also lead to cracking of the fluorite wall.
- Follow the recommended temperature outlined in the operating manual, which should always be kept next to the chamber.
What you need to know is that the compound salt spray test chamber has the ability to control humidity. And it is mainly used for salt spray wet heat alternating tests but also has a drying function. It has been widely used and recognized in many automobile industry and auto parts enterprises.
The most important thing is that the composite salt spray test chamber is one of the test equipment for “anti-moisture heat, anti-salt spray, and anti-mold” in the artificial climate environment. In addition, it is an important test equipment for the study of environmental adaptability and reliability of automobiles and other machinery. If the performance indicators are up to standard, they can be used for neutral salt spray tests and acetate spray tests.
- Touch screen controller, complete recording of temperature and humidity test curves
- Control mode: temperature, humidity, and temperature, and humidity programmable alternate control
- The RS232 interface > test time adjustable
- Unfinished tests can be continued after the power-off memory function is restored.