What is a salt spray test?

Ⅰ. What is a salt spray test? 

A salt spray tester, also known as a salt water spray tester, is one of the three test equipment used in artificial climate environments to test the corrosion resistance of materials and products. It is an authoritative test of the corrosion resistance of material protective coatings and products.

A salt spray tester is a key device for evaluating the salt spray corrosion resistance of materials and their protective coatings. It is also used to compare the process quality of similar protective coatings and assess the effectiveness of certain products in resisting salt spray corrosion.

This equipment is widely used in salt spray corrosion testing of parts, electronic components, metal material protective coatings, and various industrial products, providing a strong guarantee for product reliability.

Salt spray, a diffuse system composed of tiny salt droplets in the atmosphere, is a key component of the three-proof system for artificial environments. The salt spray tester was developed to simulate the potentially destructive effects of marine climates on products. It uses salt spray corrosion to accurately test the reliability of the tested samples.

Salt spray testing machines are primarily categorized into two types: neutral salt spray and acidic salt spray, corresponding to the "NSS" and "CASS" tests, respectively. Both tests are common methods used in artificial weathering tests for three types of products. The main difference between them lies in the standards they comply with and the test methods used.

The scientific principles are as follows:

Simulated acceleration: By creating a high-concentration chloride environment, the corrosion process of a product is simulated and accelerated by marine or chlorine-containing industrial atmospheres.

Electrochemical corrosion: Salt spray settles on the surface of the sample, forming a thin film of electrolyte. This film penetrates into the metal material, undergoing an electrochemical reaction with the metal, causing the anode (metal) to dissolve and forming corrosion products (i.e., rust).

Evaluation Basis: Corrosion resistance is comprehensively evaluated by observing the presence of corrosion, rust, blistering, and flaking on the sample surface after the test, or by measuring the time it takes for initial signs of corrosion to appear.

II. Main Types and Applications of Salt Spray Tests

Depending on the corrosion environment and test objectives, salt spray tests have evolved into various types. The four most common types are as follows:

1. Neutral Salt Spray Test

Introduction: This is the most basic and widely used test type. A 5% sodium chloride saline solution is atomized through a spray device at 35°C to create a salt spray environment with a neutral pH.

Standards: GB/T 10125. ASTM B117. ISO 9227. etc.

Applications: Suitable for rapid screening and quality comparison of basic corrosion resistance properties of metals and their alloys, metal platings, organic coatings, etc.

2. Acetic Acid Salt Spray Test

Introduction: In addition to the neutral salt spray test, glacial acetic acid is added to lower the pH of the collected solution to an acidic range of 3.1-3.3. This acidic environment significantly accelerates the corrosion process.

Standard: ASTM G85 Annex A1. ISO 9227.

Application: Primarily used for testing decorative coatings (such as copper + nickel + chromium, nickel + chromium) and anodic oxide films on aluminum alloys, revealing defects more quickly.

3. Copper-Accelerated Acetate Salt Spray Test

Introduction: Based on acetate salt spray, copper chloride is added to the salt solution to further enhance the corrosion resistance. This is the most highly accelerated conventional salt spray test currently available.

Standard: ASTM G85 Annex A2. ISO 9227.

Application: Primarily used for quickly evaluating the quality of decorative chrome-plated parts and aluminum alloy surfaces. The test cycle is much shorter than the NSS and AASS tests.

4. Alternating Salt Spray Test

Introduction: This is a more complex, comprehensive test. Rather than simply applying a continuous spray, it alternates between salt spray, dry conditions, and damp heat (high humidity) in a cycle.

Standards: GB/T 2423.18. IEC 60068-2-52.

Application: This device more realistically simulates the "wet-dry" cycle a product experiences in the real world. It is commonly used in industries with extremely high reliability requirements, such as automotive, aerospace, and electronics, and can more effectively evaluate a product's overall protection performance.

Ⅲ. User Experience:

Equipment Installation and Preparation: Ensure that the internal components of the salt spray test chamber (such as the tower spray device, nozzle, funnel, round rod, V-shaped sample holder, etc.) are properly installed. When adding water, use purified or distilled water to ensure test accuracy. The air compressor must be ready and properly connected to the equipment's air, water, and wastewater pipes. Ensure that the air pressure is within the specified range (0.3-0.4 MPa for inlet pressure and 0.07-0.17 MPa for outlet pressure).

Parameter Setting and Startup: After confirming that the equipment is functioning correctly, close the chamber lid and connect the power supply. Use the instrument to set the desired chamber temperature, saturation barrel temperature, and test time. You can also set the equipment to a continuous cycle or two spray modes based on experimental requirements.

Equipment Placement and Environment: The salt spray test chamber should be placed in a well-ventilated area away from direct sunlight. If there are windows near the chamber, curtains are recommended to block out the sunlight. For more accurate test results, it is recommended that the chamber be placed in a separate room.

Ⅳ. Maintenance

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, 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 and drain the heated water tank.

V. How to choose a professional testing partner?

Qinsun Instruments Co., LTD is a professional laboratory testing instrument manufacturer in China,Have been focusing on laboratory instrument R&D more than 30 years and have rich industry experience,Based on international testing standards,We are also the instrument supplier for BV SGS laboratory,We provide one-stop solutions for lab instruments,Free Training and Turn-Key Service,Products exported all over the world,Offer 36 month warranty and are a trustworthy partner.

In conclusion, when it comes to salt spray testing, having a comprehensive understanding of the tests themselves, along with proper equipment usage, maintenance, and the selection of a reliable testing partner, is crucial. Qinsun Instruments Co., LTD stands out as an exemplary choice, with its extensive expertise, adherence to international standards, and commitment to providing top-notch services. By partnering with Qinsun, you can ensure accurate and reliable salt spray testing results, which are vital for assessing the corrosion resistance of materials and products. This, in turn, helps in enhancing product quality, reliability, and overall performance in various industries. Choose Qinsun as your trusted testing partner and embark on a journey of excellence in salt spray testing.