Salt spray testing equipment, scientifically known as a "salt spray chamber," uses salt spray corrosion to test the reliability of the sample under test. Salt spray refers to a diffuse system composed of tiny salt droplets in the atmosphere. It is one of the three types of artificial environmental protection tests. Many companies need to simulate the destructive effects of marine climates on their products, which is why salt spray chambers are so popular. Salt spray chambers are divided into two types: neutral salt spray and acidic salt spray. The difference lies in the standards and test methods they meet. These tests, also known as "NSS" and "CASS," are the most common test methods for artificial three-layer protection.
Principle and Function
A salt spray test chamber is one of the "three defenses" (humidity, heat, salt spray, and mold) test equipment for artificial climate environments. It is a crucial test instrument for studying the adaptability and reliability of products in various environments, including machinery, defense, light electronics, and instrumentation. This salt spray corrosion test chamber can perform neutral salt spray tests in accordance with GB/T2423.17 "Basic Environmental Testing Procedures for Electronic and Electrical Products - Test Ka: Salt Spray Test Method," as well as acetic acid salt spray tests. It complies with CNS, ASTM, JIS, and ISO standards.
Advantages and Value
Salt spray testers play a significant and diverse role in the industrial sector. They help companies improve product quality. During the product design phase, salt spray testing can identify potential issues, allowing targeted optimization of materials and processes to enhance product competitiveness. They can also reduce after-sales costs, proactively address corrosion issues, reduce repair and replacement expenses, and improve customer satisfaction. Their design and operation adhere to international standards such as ISO, ASTM, and JIS, helping companies meet global market quality requirements and expand international business. They also provide a scientific verification platform for the research and development of new materials and processes, driving continuous advancements in industrial technology.
Operating Procedures
1. First, connect the test chamber power supply and air compressor power supply, and connect the air compressor air line.
2. Pour purified or distilled water into the water inlet inside the chamber and at the back of the chamber until the low water level indicator on the panel turns off; otherwise, the chamber will not operate properly.
3. Connect the drain and exhaust pipes, as shown on the previous page, with the indicator pointing left for open.
4. Fill the isolation tank with water up to the pad level to prevent salt spray leakage.
5. Preparation of the test solution:
A. Cover, Neutral Salt Spray Test (NSS Test)
a. Prepare the salt solution using sodium chloride (chemically pure, analytically pure) and distilled or deionized water to a concentration of (5% ± 0.1)% (mass percentage). The collected solution after atomization, except for the portion removed by the baffle, must not be reused.
b. The pH of the salt solution before atomization should be between 6.5 and 7.2 (at 35 ± 2°C). When preparing the salt solution, chemically pure dilute hydrochloric acid or sodium hydroxide solution may be used to adjust the pH, but the concentration must still meet the requirements in point a.
B. Metal Coating, Copper Accelerated Acetic Acid Salt Spray Test (CASS Test)
a. Dissolve sodium chloride in distilled or deionized water to a concentration of 50 ± 5 g/L.
b. Add copper chloride (CuCl2·2H2O) to solution a to a concentration of 0.26 ± 0.02 g/L (i.e., 0.205 ± 0.015 g/L anhydrous copper chloride).
c. Add an appropriate amount of glacial acetic acid to solution a to ensure that the pH of the salt spray collection solution in the test chamber is between 3.1 and 3.3. If the pH of the solution before spraying is between 3.0 and 3.1. the pH of the collected solution will generally be within the range of 3.1 to 3.3. Measure the pH of the solution with a pH meter. Alternatively, use precision pH test paper calibrated with a pH meter that can read 0.1 pH changes for routine testing. The pH of the solution can be adjusted with glacial acetic acid or sodium hydroxide.
d. To prevent nozzle clogging, the solution must be filtered before use.
Note: For metal coatings, the acetic acid salt spray test (ASS test) omits step "b" in process "B."
6. Pour salt water into the salt solution refill bottle to automatically fill the laboratory spray tower with salt water, allowing the solution to flow into the salt spray tower.
7. Fill the wet-bulb cup with water. Cover the wet-bulb thermometer with gauze, and place the end of the gauze in the wet-bulb cup.
8. Place the test piece or specimen on the rack: Arrange the angle according to the required standard. For example, a standard test piece 130×70 mm can be tilted at 15 or 30 degrees.
9. Set the test temperature: Set according to the required standard (press the "▲" key to increase, the "▼" key to decrease).
a. NSS and AASS tests: Test chamber temperature 35°C; saturated air chamber temperature 37°C (35°C to 40°C).
b. CASS test: Test chamber temperature 50°C; saturated air chamber temperature 55°C (50°C to 55°C).
10. Set the test time: 0 to 999 hours (hours; press the "+" key to increase; press the "-" key to decrease).
11. Press the power button and operate the buttons to preheat the unit to the set temperature. Note: Close the test cover and handle with care to avoid damage.
12. Press the spray button:
a. Open the outlet valve on the front of the air compressor and adjust the pressure to 0.2-0.4 MPa.
b. Adjust the pressure regulating valve to 0.07-0.17 MPa. The pressure can be read on the pressure gauge (clockwise to increase, counterclockwise to decrease).
13. Press the timer button to count down the timer.
14. After the test is complete, turn off all switches in order.
15. If any abnormalities occur during the test, refer to the functional abnormality diagnosis table for corrective measures.
Determination Methods
Salt spray test results can be determined using the following methods: grading, weighing, corrosion product appearance, and statistical analysis of corrosion data.
The grading method classifies the percentage of the corrosion area to the total area into several levels using a specific method, with each level used as the basis for acceptance. This method is suitable for evaluating flat samples.
The weighing method uses the weight of the sample before and after the corrosion test to calculate the weight loss due to corrosion and evaluate the corrosion resistance of the sample. It is particularly suitable for evaluating the corrosion resistance of certain metals.
The corrosion product appearance method is a qualitative method that determines whether the product exhibits corrosion after the salt spray test. This method is commonly used in general product standards.
The statistical analysis of corrosion data provides methods for designing corrosion tests, analyzing corrosion data, and determining the confidence level of the corrosion data. It is primarily used for analyzing and compiling statistics on corrosion conditions, rather than for assessing the quality of specific products.
Core Technologies
1. Precise Simulation of Corrosive Environments: Salt spray test chambers precisely control salt water concentration, temperature, and spray volume to simulate extreme corrosive environments such as marine environments and industrial pollution. Core technologies include:
◎ Constant Temperature Control System: Ensures stable chamber temperature, simulating real-world conditions.
◎ Atomization System: Utilizes high-efficiency atomizing nozzles to evenly distribute salt water, ensuring test repeatability and reliability.
◎ Automatic Water Replenishment and Drainage: Intelligent design reduces manual intervention and improves test efficiency.
2. Intelligent Operation and Monitoring: Modern salt spray test chambers are equipped with intelligent control systems that support remote monitoring, data logging, and alarm functions. Users can view test status in real time via the touchscreen or mobile app, ensuring controllable and transparent testing.
3. Environmentally Friendly and Energy-Saving Design: Utilizes efficient energy-saving technologies to reduce energy consumption, and is equipped with a wastewater treatment system to minimize environmental pollution.
Application Areas
1. Automotive Industry: Automotive parts such as bodies, chassis, and fasteners require corrosion resistance testing in salt spray environments to ensure vehicle life in coastal areas or during winter snowmelt.
2. Electronics and Electrical Industry: Electronic components and circuit boards are prone to corrosion in high-humidity and high-salinity environments. Salt spray test chambers can help companies detect problems early and improve product reliability.
3. Building Materials: The corrosion resistance of materials such as metal coatings and anti-corrosion paints directly impacts the service life of buildings. Salt spray test chambers provide a scientific basis for material research and development and quality inspection.
4. Aerospace: Aircraft parts face extreme corrosion challenges in high-altitude and marine environments. Salt spray test chambers are a crucial tool for ensuring their safety.
Maintenance Methods
1. Regularly lubricate the air compressor of the salt spray corrosion test chamber.
2. Before restarting the chamber for testing after an extended period of inactivity, inspect all electrical systems.
3. If the nozzle becomes clogged, remove the nozzle and clean it with alcohol, xylene, or 1:1 hydrochloric acid, or use an ultra-fine steel wire to unclog it. However, be careful not to damage the surface finish of the nozzle cavity, which could affect spray efficiency.
4. Regularly check the function of the air control valve.
5. If testing is not performed for an extended period, open the saturator and drain the water. The water in the saturator should also be replaced regularly during normal operation.
6. Do not reuse the test salt solution if it has not been used for more than one week to avoid affecting the test.
7. After the test, clean the chamber and keep it as dry as possible.
8. If any electrical components on the control panel of the salt spray corrosion test chamber require replacement, this should be done under the manufacturer's guidance to avoid any complications.
9. After the test, clean the chamber interior and drain the heated water tank.
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