Salt Spray Chamberor corrosion test chamber is the most popular device used for metal testing. It simulates the fog laden environment to see how the coating will behave to such condition. It gives an estimation of behaviour in real working conditions. You are simultaneously testing the sample for salt laden fog, humidity, perspiration and temperature. However, the temperature is not very high, but hot enough for testing.
How to Perform the test?
According to JIS, the test sample needs to be placed at an angle of 20°. The chamber has slots made at this particular angle to place the sample easily. There is an atomiser in the centre to produce fog. It takes NaCl solution from the reservoir tank. This tank has capacity of approx. 60 litres which ensure non-stop test running. The fog spreads evenly in every corner of the chamber. A see-through, canopy style lid allows the operator to see the inside of the chamber. However, due to fog, the visibility is very low. Once the sample is placed, the test has started to defined hours, the operator cannot open the chamber. It violates the testing guidelines issued by ASTM. If due to power failure or for some reason canopy has to be opened, you need to initiate the purging first. This helps in settling the fog by converting it into the mist. Once the fog settles, the canopy can be opened, observations made and closed again to restart the test.
Observations are made by visual inspection only. No data is generated, no readings are displayed. You only see the sample to check if it sustains the test or failed.
Why is Purging important?
Salt Spray Chamber creates salt laden fog which has the tendency to corrode the material. If this fog comes in contact with objects in the surrounding, it may affect them as well. Purging allows the fog to settle by converting it into the mist. Auto and Manual air purging can be done. When the test is completed, the machines automatically goes into purging mode to allow the operator to open the canopy. Manual air purging is required every time when you want to stop the test in-between and restart again after some time. The operator needs to start the air purging by pressing the button.
This fog is quite harmful for metals. Therefore, all the components inside the corrosion test chamber are made up of fibre. All the precautions are taken for the high shelf life of the machine.