Quick operation procedure for salt spray tester
I. Startup operation: From basic confirmation to spray startup
1. Pre - conditions: Three core inspections
Before starting up, it is necessary to complete the verification of key conditions one by one to avoid test failure due to insufficient preparation.
Power supply and air source: Connect to a stable power supply matching the rated voltage of the equipment (e.g., 380V/50Hz), connect to a compressed air source, and confirm that the reading of the intake air pressure gauge is ≥2 Kg (insufficient air source pressure will directly result in the spray pressure not meeting the standard).
Valve status: Open the automatic water supply valve (to ensure continuous water replenishment during equipment operation), and close the drain valves of the pressure tank and the experimental box (to prevent pressure loss due to water leakage or water accumulation in the box).
Container cleaning: Check that there is no residual salt stain or water in the pressure barrel and saltwater barrel. (If there is, it needs to be rinsed with clean water in advance to avoid affecting the purity of the solution in this test.)
2. Panel startup: Status monitoring and abnormal handling
After turning on the power switch and the operation switch of the operation panel, immediately pay attention to the status of the indicator lights:
- If the red light for low water level/low brine water is on and an alarm goes off, a rapid response is required.
- Low water level: Add distilled water to the maximum water level line of the water tank (lack of water will cause the heating tube to dry burn).
- Low salt water: Prepare the salt water according to the standard and pour it into the salt water bucket (spraying will be interrupted if there is insufficient salt water). The equipment cannot enter the spraying state before the alarm is cleared.
3. Brine preparation: Specification accurate to "gram"
The purity of the salt spray test solution directly affects the corrosion results. The following requirements must be strictly followed:
Raw material selection: Reagent-grade sodium chloride (purity ≥ 99.5% to avoid impurity interference with the corrosion rate) + distilled water (or pure water with a total dissolved solids content ≤ 200 ppm to prevent scaling by calcium and magnesium ions) must be used.
Concentration calculation: Prepare a saline solution with a mass concentration of 5 ± 1% (e.g., add 500 g of sodium chloride to 10 L of water, and 750 g of sodium chloride to 15 L of water. The error should be controlled within ±150 g);
Dosage reference: 15L of the prepared saline solution can be used continuously for about 48 hours. It is recommended to prepare enough at one time before the experiment to avoid adding more in the middle, which may break the concentration balance of the solution.
4. Sample placement: The angle determines the validity of the test
Fix the sample to be tested on the special support inside the experimental box. Two points need to be noted:
Inclination angle: The main test surface of the specimen forms an angle of 15° - 30° with the plumb line (this angle allows the salt spray to evenly cover the surface, avoiding liquid accumulation or blind spots - if placed vertically, the salt spray tends to flow along the surface, resulting in excessive local corrosion; if the inclination is too large, the amount of salt spray adhesion will be reduced).
Avoid stacking: Keep sufficient spacing between specimens without mutual shielding (stacking will prevent the inner-layer samples from being exposed to the salt spray, rendering the test results invalid).
5. Parameter setting and spray startup
Time setting:
- For ordinary models: Directly rotate the timer to the required test duration (e.g., 24 hours, 48 hours).
- Type B programmable machine: Write the spraying program according to the product standard (e.g., cycle of "spray for 30 minutes → pause for 30 minutes", or "continuous spraying for 12 hours");
Start spraying: First, turn on the timing switch (for Type B machines, the "programming control switch" needs to be turned on simultaneously), and then turn on the spray switch. At this time, keep a close eye on the spray pressure gauge. The pointer should quickly stabilize at 1 Kg (if the pressure is too high, the spray volume will exceed the standard; if it is too low, the spray will be unevenly dispersed). After confirming that the pressure is normal, the equipment officially enters the test state.
II. Operation process: Management and control of four core parameters
1. Basic supply: The "lifeline" that cannot be interrupted
During operation, it is necessary to continuously ensure the stability of power supply, water supply, and gas supply.
- Power supply: Avoid power interruption during the process (a UPS can be equipped). A power outage will cause the test to be interrupted and it will need to be restarted.
- Water source: Pay attention to the water level in the water tank. When it is insufficient, replenish distilled water in time (a low water level alarm will be triggered and the spraying will be paused if there is a water shortage).
- Air source: Regularly check the pressure of the air compressor and maintain the intake pressure at 2 Kg (a drop in the air source pressure will result in insufficient spray pressure, and the output of the air compressor needs to be adjusted).
2. Temperature control: Two "key figures"
The device has two built - in temperature control points, which directly affect the quality of the salt spray.
Pressure barrel temperature: It is necessary to maintain at 47±1℃ (High temperature causes the saltwater to vaporize and form a fine and uniform salt spray. If the temperature is too low, the salt spray particles will be too large and prone to sedimentation; if it is too high, the salt spray will evaporate too quickly).
Brine tank temperature: It needs to be stabilized at 35±1℃ (simulating the corrosion temperature in the natural environment. At this temperature, the corrosiveness of the salt spray is closest to the actual scenario).
If the temperature deviates during operation, it is necessary to check whether the heating tube is working properly and whether the heat dissipation port is blocked (for example, dust covering can affect heat dissipation and cause the temperature to be too high).
3. Humidity requirement: 85% is the bottom line
The relative humidity inside the test chamber must be ≥85% (high humidity is a necessary condition for salt spray corrosion—if the humidity is insufficient, the salt spray will evaporate rapidly, and a continuous corrosive liquid film cannot be formed on the surface of the test specimen, resulting in a lighter test result). If the humidity does not meet the standard, check whether the sealing rubber strip of the chamber door is aged (poor sealing will cause moisture leakage), or add a small amount of distilled water into the chamber (to increase the humidity).
4. Spray volume verification: Let the data speak
The spray volume is the core indicator for judging the effectiveness of the test and needs to be verified according to the following methods:
Collection containers: Place 2 - 3 standard collection containers (such as graduated cylinders with funnels, with an opening area of 100 cm²) evenly inside the experimental box.
Measurement requirements: The amount of brine collected per hour should be between 1.0 - 2.0 ml (if it is lower than 1.0 ml, it indicates that the spray volume is insufficient and the corrosion rate is slow; if it is higher than 2.0 ml, it indicates that the spray is excessive, which will lead to excessive corrosion of the test specimens).
Average calculation: The spray volume needs to be continuously collected for at least 16 hours to obtain the average value (the error of a single measurement is large, and the long - term average can better reflect the real spray volume). —— If the average value deviates from the range, the nozzle needs to be cleaned (nozzle blockage is a common cause) or the spray pressure needs to be adjusted.
III. Shutdown and Maintenance: The Key to Extending Equipment Lifespan
1. Shutdown process: Operate in sequence to prevent damage
After the experiment is over, the following steps must be strictly followed:
-: Turn off the spray switch (stop the generation of salt spray);
-: Turn on the defogging switch (extract the residual salt fog in the box through the fan or recover the fog water through the condensation system);
- Wait until the fog in the test chamber has completely dissipated (about 5 - 10 minutes, which can be judged by observing the glass of the chamber door), and then open the chamber lid to take out the test specimens. It is prohibited to directly open the lid (if the lid is opened without defogging, the salt spray will overflow instantly, corroding the surrounding equipment or the skin and respiratory tracts of personnel).
2. Maintenance: Differences between daily maintenance and maintenance during long-term disuse
Daily maintenance (once a month):
- Clean the pressure tank, experimental box, and salt water tank: Rinse the internal salt stains and scale with clean water (residual salt stains will corrode the inner wall of the container, and scale will affect the heat conduction efficiency of the heating tube).
- Clean the nozzle: Handle the nozzle with care when disassembling it (avoid damaging the nozzle opening). Rinse it with clean water 2 - 3 times. (A clogged nozzle can lead to a decrease in the spray volume or uneven spraying, which is a common fault affecting the test results.)
Long-term deactivation (more than 1 week):
- Completely drain all the water and brine from all containers (including the pressure tank, brine tank, and water tank).
- Rinse each container with clean water 2 - 3 times. After drying, close the cabinet door (residual salt will slowly corrode the metal components inside the equipment, causing valve jamming and pipeline blockage).