Compound Salt Spray Test Chamber FAQ Guide

13 min readMay 30, 2023

1. What is a compound salt spray test chamber?

The corrosion of metal materials mostly occurs in the atmosphere, which contains corrosive components and corrosive factors such as oxygen, humidity, temperature changes, pollutants, and so on. The corrosion of salt spray to metal salts is mainly caused by the electrochemical reaction of conductive salt solutions entering the metal, forming a micro-battery system of “low potential metal electrolyte solution — high potential impurities”, electron transfer occurs, and the metal dissolves as an anode.

The main function of the compound salt spray corrosion process is chloride ions. It has a strong penetrating force, which easily penetrates the metal oxide layer into the metal and destroys the passivation state of the metal. At the same time, chloride has less hydration energy. It easily adsorbs on metal surfaces and replaces oxygen in the oxide layer that protects the metal from destroying the metal.

The programmable compound salt spray test chamber not only has the function of a basic compound salt spray test chamber but also combines the function of alternating cycle salt spray testing to provide test environments such as obsessive corrosion and filamentous corrosion. Test environments such as hot air drying, damp heat, and forced drying.

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.

2. What is the function of the compound salt spray test chamber?

Although it is called the Salt Spray Test and the Salt Spray Test Chamber, the name is somewhat misleading. Sprays usually come in the form of fog or ultra-fine mist, creating an environment that accelerates corrosion. This situation 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

3. What are the characteristics of the compound salt spray test chamber?

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.

4. Why should a company use a compound salt spray test chamber?

It doesn’t take much evidence to understand how corrosion can negatively affect our lives, and it goes beyond the anachronistic sight of rust.

Drivers of northern climates are well aware of the importance of corrosion-resistant materials. The accumulation of salt on winter roads wreaks havoc on the landing gear of cars, especially those best described as “egg beaters” or “clumsy ones.” Corrosion poses a threat to the safety of the driver and to all other people on the road.

Just as automotive companies focus some of their research efforts on developing corrosion-resistant components, municipalities are also concerned about the roads themselves. The combination of salt and water can erode asphalt and concrete, sometimes below the surface. Potholes come with them. Researchers are tackling this problem by developing pavement solutions that are waterproof and salt-resistant.

Then there’s a very real public health problem. A 2019 report by the National Society of Corrosion Engineers estimated the direct cost of corrosion in drinking water and sewer systems in the United States at $80 billion. If left unaddressed, contaminated water poses a threat to citizens across the country.

5. What is the application of the compound salt spray test chamber?

The compound salt spray test chamber has the ability to control humidity, mainly used for salt spray humidity and heat alternating testing, but also has a drying function, in many automotive industry and auto parts enterprises has been widely used and recognized. the compound salt spray test chamber is one of the test equipment for “anti-humidity and heat, anti-salt spray, anti-mildew” in an artificial climate environment. It is important testing equipment for studying the environmental adaptability and reliability of automobiles and other machines. The performance indicators meet the standard and 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.

6. How to install a 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

The 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 chamber varies by model, here is a small formula to help determine the capacity of the desalinate cartridge: 1600 TDS / 17.12 ppm = capacity (in gallons). When three-quarters of the grain changes to the color it uses, the cartridge should be changed.

3) Salt spray nozzle assembly

The compound salt spray chamber is equipped with a nebulization nozzle, but if you need to replace it, you may need to take the following steps:

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-810filter, 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

To prevent back pressure in the chamber, it must be vented. When setting up the chamber, be sure to install a non-corrosive three-inch tube from the exhaust chamber to a point outside the building. This exhaust outlet should be as short, straight, and gently tilted down from the chamber to avoid any liquid traps. It should also shield against the influence of wind or air currents.

While a flexible hose can be an option, you must be diligent in ensuring that it does not sag in the section, creating a liquid trap. If the length of the exhaust pipe is more than 10 feet, a two-inch line should be used. If your pipe must exit through the roof upwards, use a T-fitting instead of an elbow. Align the T so that an 18-inch drop line and drain can be added to ensure that the exhaust line remains clear at all times.

5) Salt chamber for gas supply

Compound salt spray chambers require clean, oil-free compressed air, and valves labeled “air” have been installed at the rear end of the compound 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 operate between 6–10, depending on the model.

7. How to operate your compound salt spray test chamber?

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. The heater located inside the tower is controlled by a thermostat that is factory set to maintain the tower temperature of 114 degrees Fahrenheit (45.5 degrees Celsius).
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. Adjustments shall be made in increments not exceeding one-eighth. Before making other adjustments, be sure to allow enough time for stabilization.

8. What is the start-up procedure for using a compound salt spray test chamber?

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 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.

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.

13) Check the normal operation of the salt spray nozzle.

14) 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.

9. What are the test temperature and humidity required for the compound salt spray test chamber?

The critical relative humidity of metal corrosion is about 70%. When relative humidity reaches or exceeds this critical humidity, the salt will deliquefy to form an electrolyte with good electrical conductivity. When the relative humidity decreases, the concentration of the salt solution increases until the crystalline salts precipitate and the corrosion rate decreases accordingly. When the temperature rises, the molecular movement intensifies and the salt spray corrosion rate is high. The International Electrotechnical Commission pointed out that for every 10 ° C increase in temperature, the corrosion rate increases by 2 to 3 times, and the conductivity of the electrolyte increases by 10 to 20%. For the neutral salt spray test, it is generally considered appropriate to choose a test temperature of 35 ° C.

10. What is the solution concentration standard required for the compound salt spray test chamber?

When the concentration is less than 5%, the corrosion rate of steel, nickel, and brass increases with the increase of concentration, and when the concentration exceeds 5%, the corrosion rate of these metals decreases with the increase of concentration. This is because, in the range of low concentrations, the oxygen content increases with the increase of salt concentration; When the salt concentration increases to 5%, the oxygen content reaches relative saturation, and if the salt concentration continues to increase, the oxygen content decreases accordingly. As the oxygen content decreases, the depolarization capacity of oxygen also decreases, that is, the corrosive effect decreases. For metals such as zinc, cadmium, copper, etc., the corrosion rate always increases with the concentration of the salt solution.

The direction of settlement of the salt mist is close to the vertical direction. When the sample is placed horizontally, its projection area is the largest, and the sample surface is subjected to the most salt spray, so the corrosion is the most severe. The results show that when the steel plate is at a 45-degree angle with the horizontal line, the weight reduction per square meter is 250g. When the plane of the steel plate is parallel to the vertical line, the weight loss of corrosion is 140 grams per square meter. GB/T 2423.17–93 standard stipulates that flat samples should be placed at a 30-degree angle vertically.

11. How to maintain a compound salt spray test chamber?

When we use the compound salt spray test chamber at the end of each test or test, we should empty and wash the solution of the measuring cup in time to avoid the accumulation of salt solution crystals, which will affect the calculation of sedimentation.

When the machine is left unused for a long time, the water in the saturated tank should be let out of it. The water in the saturator should also be replaced normally at a certain time during normal use. When restarting the test, all electrical systems should be inspected.

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;

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.