The Salt Spray test is a laboratory test that is conducted to test the corrosion resistance properties of several metals and coatings. This test is conducted by using a machine which is termed a Salt Spray chamber. Let us dive into the details of this testing chamber. All the necessary information regarding the salt spray test chamber will be covered in this blog. So, let’s start.
What is the Salt Spray test and how many test methods are in SST?
The salt spray test is a laboratory test which is done to test the corrosion resistance properties of metals. In SST, a 5% solution of NaCl is made and salt fog is produced in the salt spray chamber. The sample to be tested is placed inside the test chamber and changes on the sample would be monitored.
Test methods
- Three test methods are used for conducting a salt spray test.
- Acetic Acid Salt Spray test
- Material for testing: Chromium Plating, Cadmium Plating on Zinc and steel.
- 5% Neutral Salt Spray Test
- Material for testing: Platings and coatings on metallic parts.
- CASS( Copper Accelerated Salt Spray Test).
- Material for testing: Decorative Copper Nickel chrome plating, Zinc die castings, Anodized Aluminium.
History of SST
The first testing method was developed in 1910. It was not standardized for 30 years. It was done after 30 years on the release of ASTM B117 in 1939. The earliest standard varies significantly in which the level of salt is 20%. This concentration of salt was high and it causes problems in accurate test results. Later, it was discovered that reducing the salt concentration to 5% would accelerate the test result without any negative drawbacks. So, in 1954 the ASTM standard was revised with a concentration of 5% NaCl.
Material required for Salt Spray Test
The following material can be salt spray tested.
- ED coating parts
- Painted Parts
- Phosphate Parts
- Powder Coating Parts
- Zinc Plating and Zinc Alloy Platings
Preparation of solution for SST
Preparing a solution for SST chamber is carried out in a very easy method. All you have to do is just take fresh DM water add 5% NaCl in the water and mix it well.
Most importantly, check the pH of the DM water before dissolving in the NaCl.
Parameters required for Salt Spray testing
For conducting a salt spray test, the following parameters are required.
- pH: 6.5-7.2
- Temperature of test chamber: 35+-1degree
- Spray Pressure: 0.7-1.8kg/cm2
- Temperature of saturated tank: 47+-1degree
- Fog Collection: 0.85-2.0ml/h for 80cm2.