Which Values In The Salt Spray Test Determine The Corrosion Results
Most of the corrosion of metal materials occurs in the atmospheric environment, and the atmosphere contains corrosion components and corrosion factors such as oxygen, humidity, temperature changes and pollutants. Salt spray corrosion is a common and most destructive atmospheric corrosion.
The most common in our daily life is the artificial accelerated simulated salt spray environmental test. The artificial accelerated simulated salt spray test is an environmental test that mainly uses the artificial simulated salt spray environmental conditions created by the salt spray test equipment to evaluate the corrosion resistance of products or metal materials. Generally, the results of the salt spray test will be affected by various factors, and the salt spray test of the product is mainly used to assess the corrosion resistance of the product or metal material. In general, salt spray test can be affected by the concentration of salt solution, lofting Angle, pH value of salt solution, test temperature and humidity, salt spray settling amount and spray method. The following details the main factors affecting the results of the salt spray test, hope to be helpful to you.
The higher the test temperature, the faster the corrosion rate of the salt spray. According to the International Electrotechnical Commission, "for every 10 ° C increase in temperature, the corrosion rate increases two to three times and the conductivity of the electrolyte increases by 10 to 20 percent." This is because the temperature increases, the molecular movement increases, and the chemical reaction speeds up. For the neutral salt spray test, most scholars believe that the test temperature of 35℃ is more appropriate. If the test temperature is too high, the salt spray corrosion mechanism is very different from the actual situation.
A lower pH value indicates a higher concentration of hydrogen ions in the solution, which means the solution is more acidic and corrosive. By conducting salt spray tests on electroplated parts such as Fe/Zn, Fe/Cd, Fe/Cu/Ni/Cr, it can be observed that the acid spray test (ASS) with a pH value of 3.0 is more severe than the neutral salt spray test (NSS) with a pH value of 6.57.2, and the severity of the test is approximately 1.52.0 times that of the latter. It should be noted that the pH value of salt solutions may vary due to environmental factors.
For materials such as steel, nickel, and brass, the corrosion rate increases with increasing concentration in salt solutions below 5%.
However, when the concentration of salt solution exceeds 5%, the corrosion rate of these metals decreases with increasing concentration.
This phenomenon can be explained by the oxygen content in the salt solution. The oxygen content in salt solution is closely related to the concentration of salt. In the low concentration range, as the salt concentration increases, the oxygen content also increases.
However, when the salt concentration reaches 5%, the oxygen content tends to be relatively saturated. If the salt concentration continues to increase, the oxygen content will actually decrease. As the oxygen content decreases, the depolarization ability of oxygen also decreases, thereby weakening the corrosion effect.
However, for metals such as zinc, cadmium, and copper, their corrosion rate always increases regardless of the increase in salt solution concentration.
The results show that when the steel plate is at a 45° Angle to the horizontal line, the corrosion loss per square meter of the surface is 250 grams. When the steel plate plane is parallel to the vertical line, the corrosion loss per square meter of the surface is only 140 grams. In other words, the change of placement Angle has a significant impact on the degree of corrosion, the closer the placement Angle is to the horizontal, the more serious the degree of corrosion, and the closer the placement Angle is to the vertical, the degree of corrosion is relatively light.
Traditional spray methods, such as pressure spray and spray tower method, have obvious disadvantages, including poor settling uniformity of salt spray and large diameter of salt spray particles. In order to solve these problems, the ultrasonic atomization method uses the principle of ultrasound to atomize the salt solution into a salt spray and spread it to the test area. This method improves the settling uniformity of salt spray. In addition, due to the small diameter of the salt spray particles generated by ultrasonic atomization, different spray methods may also have an impact on the pH value of the salt solution.
As an excellent manufacturer of salt spray test equipment and developer of environmental reliability testing equipment in China, we are committed to providing high-quality salt spray solutions to meet the needs and requirements of customers. Our salt spray test equipment are manufactured using advanced technology and processes to ensure their stability and reliability in salt spray testing. We focus on precise control of the size and distribution of salt spray particles, as well as atomization uniformity, to ensure the accuracy and repeatability of test results.
In addition to the standard pressure spray method and spray tower method, we also use ultrasonic atomization technology. This advanced spray method can produce fine salt spray particles, improve the sedimentation uniformity during the test process, and have a small impact on the pH value of the salt solution. Our environmental reliability testing equipment not only includes the salt spray test equipment, but also covers other key testing equipment, such as temperature and humidity test chamber, vibration shaker, drop test machine, etc., to meet customers' needs for comprehensive environmental reliability testing.
The most common in our daily life is the artificial accelerated simulated salt spray environmental test. The artificial accelerated simulated salt spray test is an environmental test that mainly uses the artificial simulated salt spray environmental conditions created by the salt spray test equipment to evaluate the corrosion resistance of products or metal materials. Generally, the results of the salt spray test will be affected by various factors, and the salt spray test of the product is mainly used to assess the corrosion resistance of the product or metal material. In general, salt spray test can be affected by the concentration of salt solution, lofting Angle, pH value of salt solution, test temperature and humidity, salt spray settling amount and spray method. The following details the main factors affecting the results of the salt spray test, hope to be helpful to you.
Temperature and humidity
Temperature and relative humidity affect the corrosion of salt spray. The critical relative humidity for metal corrosion is about 70%. When the relative humidity reaches or exceeds this critical humidity, the salt deliqueses to form a conductive electrolyte. When the relative humidity is reduced, the concentration of the salt solution will increase until the crystalline salt is precipitated, and the corrosion rate will decrease accordingly.The higher the test temperature, the faster the corrosion rate of the salt spray. According to the International Electrotechnical Commission, "for every 10 ° C increase in temperature, the corrosion rate increases two to three times and the conductivity of the electrolyte increases by 10 to 20 percent." This is because the temperature increases, the molecular movement increases, and the chemical reaction speeds up. For the neutral salt spray test, most scholars believe that the test temperature of 35℃ is more appropriate. If the test temperature is too high, the salt spray corrosion mechanism is very different from the actual situation.
The pH value of salt solution
The pH value of the salt solution is one of the main factors affecting the results of the salt spray test.A lower pH value indicates a higher concentration of hydrogen ions in the solution, which means the solution is more acidic and corrosive. By conducting salt spray tests on electroplated parts such as Fe/Zn, Fe/Cd, Fe/Cu/Ni/Cr, it can be observed that the acid spray test (ASS) with a pH value of 3.0 is more severe than the neutral salt spray test (NSS) with a pH value of 6.57.2, and the severity of the test is approximately 1.52.0 times that of the latter. It should be noted that the pH value of salt solutions may vary due to environmental factors.
Salt solution concentration
The effect of salt solution concentration on corrosion rate is closely related to the material and coating type.For materials such as steel, nickel, and brass, the corrosion rate increases with increasing concentration in salt solutions below 5%.
However, when the concentration of salt solution exceeds 5%, the corrosion rate of these metals decreases with increasing concentration.
This phenomenon can be explained by the oxygen content in the salt solution. The oxygen content in salt solution is closely related to the concentration of salt. In the low concentration range, as the salt concentration increases, the oxygen content also increases.
However, when the salt concentration reaches 5%, the oxygen content tends to be relatively saturated. If the salt concentration continues to increase, the oxygen content will actually decrease. As the oxygen content decreases, the depolarization ability of oxygen also decreases, thereby weakening the corrosion effect.
However, for metals such as zinc, cadmium, and copper, their corrosion rate always increases regardless of the increase in salt solution concentration.
Sample placement Angle
The position Angle of the sample has a significant effect on the result of salt spray test. The sedimentation direction of the salt spray is close to the vertical direction. When the sample is placed horizontally, its projected area is the largest, and the sample surface is exposed to the most salt spray, resulting in the most serious corrosion.The results show that when the steel plate is at a 45° Angle to the horizontal line, the corrosion loss per square meter of the surface is 250 grams. When the steel plate plane is parallel to the vertical line, the corrosion loss per square meter of the surface is only 140 grams. In other words, the change of placement Angle has a significant impact on the degree of corrosion, the closer the placement Angle is to the horizontal, the more serious the degree of corrosion, and the closer the placement Angle is to the vertical, the degree of corrosion is relatively light.
The settling amount and spraying method of salt spray
The fineness of salt spray particles is closely related to the surface area formed, and the finer the surface area of the particles is larger, so that more oxygen can be absorbed and the corrosion is enhanced. In nature, more than 90% of salt spray particles are less than 1 micron in diameter. The results show that the oxygen adsorption on the surface of the salt spray particles with a diameter of 1 micron is relatively balanced with the dissolved oxygen in the particles. In other words, no matter how small the salt spray particles are, the amount of oxygen adsorbated does not increase.Traditional spray methods, such as pressure spray and spray tower method, have obvious disadvantages, including poor settling uniformity of salt spray and large diameter of salt spray particles. In order to solve these problems, the ultrasonic atomization method uses the principle of ultrasound to atomize the salt solution into a salt spray and spread it to the test area. This method improves the settling uniformity of salt spray. In addition, due to the small diameter of the salt spray particles generated by ultrasonic atomization, different spray methods may also have an impact on the pH value of the salt solution.
As an excellent manufacturer of salt spray test equipment and developer of environmental reliability testing equipment in China, we are committed to providing high-quality salt spray solutions to meet the needs and requirements of customers. Our salt spray test equipment are manufactured using advanced technology and processes to ensure their stability and reliability in salt spray testing. We focus on precise control of the size and distribution of salt spray particles, as well as atomization uniformity, to ensure the accuracy and repeatability of test results.
In addition to the standard pressure spray method and spray tower method, we also use ultrasonic atomization technology. This advanced spray method can produce fine salt spray particles, improve the sedimentation uniformity during the test process, and have a small impact on the pH value of the salt solution. Our environmental reliability testing equipment not only includes the salt spray test equipment, but also covers other key testing equipment, such as temperature and humidity test chamber, vibration shaker, drop test machine, etc., to meet customers' needs for comprehensive environmental reliability testing.
