Fasteners are responsible for creating non-permanent joints. Sometimes, due to corrosion, they lose their texture and create a non-movable joint. Thus, in order to separate the joint, you might have to break the joint. A very common example of this situation is fasteners attached to the bathroom knobs. After some years, due to excessive exposure to water and humid environment, they get corroded. So, when you try to change them, you have to struggle a lot. Well, this is just a domestic example. Now, when these fasteners are used in very critical applications like aerospace, automotive, etc. this corrosion of fasteners may lead to failure of the module.
How to test the corrosive properties of the fasteners?
Corrosion is initiated by the atmosphere of the surrounding. If it has humid air, salt laden, the chemical laden environment around the process of corrosion accelerates. Thus, to test the behaviour of the fastener in real working conditions, the salt spray chamber simulates the salt laden environment inside the chamber. It creates a fog at a certain temperature and the sample is kept inside the chamber for certain hours, according to the test procedure mentioned by the regulatory authority.
How Corrosion Test Chamber simulates the real working conditions?
Salt Spray Chamber has a heater to attain the desired temperature. The range may vary from ambient to 60°C. It has a NaCl reservoir tank that supplies the solution for the non-stop test. The atomiser creates the foggy effect by combining NaCl with water. The tower style atomiser makes sure that fog is being distributed uniformly throughout the chamber. It is equipped with double layered glass wool insulation and a fibre sheet to keep the temperature distribution uniform and maintained.
Standard operating procedure of Salt Spray Chamber
- According to ASTM, once the test process starts, it should not be stopped until the cycle completes.
- The test sample is placed at an angle of 20°. The chamber has slots made to place the samples at this angle.
- It has a see-through canopy, to see what’s happening inside. However, due to foggy conditions, there is zero visibility.
- To perform the test, place the sample inside the chamber and preset the temperature, humidity level and time in the machine.
- It is important to maintain the pH level 7 of the solution. Therefore, it is important to keep the machine in ideal lab conditions.
- Once the test is over, the automatic air purging will start and the canopy is supposed to be open after that.
With a visual inspection of the sample, the behaviour of fasteners can be assessed.