Reasons Affecting the Test Results of Salt Spray Corrosion Test Chamber

1. Test temperature and humidity:

The temperature and humidity of the salt spray test chamber will affect the corrosion effect of salt spray. For example, the neutral salt spray test: the chamber temperature is 35, the saturated barrel is 47, and the acid test: the chamber temperature is 50, and the saturated barrel is 63. The humidity in the chamber is about At around 95%, the critical relative humidity for metal corrosion is around 70%. When the relative humidity reaches or exceeds this critical humidity, the salt will deliquesce to form an electrolyte with good electrical conductivity. When the relative humidity decreases, the concentration of the salt solution will increase until the crystalline salt is precipitated, and the corrosion rate will decrease accordingly.

2. The PH value of the salt solution:

The pH value of the salt solution in the salt spray corrosion test chamber is one of the main factors affecting the results of the salt spray test. The lower the pH value, the higher the hydrogen ion concentration in the solution, the stronger the acidity and the stronger the corrosiveness.

The pH value of the salt solution will change under the influence of environmental factors. For this reason, the salt spray test standards at home and abroad have stipulated the pH value range of the salt solution, and put forward a method to stabilize the pH value of the salt solution during the test, so as to reduce the pH value of the salt solution. Risk of inaccurate experimental results due to changes in the pH of the saline solution.

3. Salt spray deposition amount and spray method:

The finer the salt spray particles in the salt spray test chamber, the larger the surface area formed, the more oxygen adsorbed, and the stronger the corrosiveness. More than 90% of salt spray particles in nature have a diameter of less than 1 micron. Research results show that the amount of oxygen adsorbed on the surface of salt spray particles with a diameter of 1 micron is relatively balanced with the amount of oxygen dissolved inside the particles. No matter how small the salt spray particles are, the amount of oxygen adsorbed will no longer increase.

4. Concentration of salt solution: 

The effect of the concentration of the salt solution on the corrosion rate of the salt spray test chamber is related to the type of material and coating. When the concentration is below 5%, the corrosion rate of steel, nickel and brass increases with the increase of the concentration; when the concentration is greater than 5%, the corrosion rate of these metals decreases with the increase of the concentration. The above phenomenon can be explained by the oxygen content in the salt solution. The oxygen content in the salt solution is related to the salt concentration. In the low concentration range, the oxygen content increases with the increase of the salt concentration. However, when the salt concentration increases to At 5%, the oxygen content reaches relative saturation, and if the salt concentration continues to increase, the oxygen content decreases accordingly. When the oxygen content decreases, the depolarization ability of oxygen also decreases, that is, the corrosion effect is weakened. However, for metals such as zinc, cadmium, and copper, the corrosion rate of the salt spray test chamber always increases with the increase of the salt solution concentration.