Salt Spray testing is a popular corrosion testing procedure which is used to check the corrosion resistance strength of surface coatings and different alloys. The alloys that are tested are generally metallic. Although ceramics, stone, polymers can be tested. The test is conducted using a Salt spray testing machine, which is an accelerated corrosion testing machine that provides a corrosive attack to the coated samples in order to evaluate the suitability of plating and coatings.

Types of corrosion tests

Variation in the corrosion test solution depends upon the materials to be tested. The most common test which is used to test the corrosion resistance strength of steels is NSS i.e. Neutral Salt Spray Test which reflects the fact that the type of solution is prepared to a pH of 6.5 to 7.2. Many companies make use of seawater solution to perform the test. Other test solutions are ASS i.e. acetic acid and CASS i.e. acetic acid with copper chloride. Both the solutions are used to evaluate the corrosion resistance strength of electroplated copper, nickel, chromium, decorative coatings, or anodized aluminum. It has pH value of 3.1 to 3.3.

Applications of corrosion test

  • Enables to make a quick comparison between actual and expected corrosion resistance strength.
  • The result of the test can be compared with the expected sample to measure the pass or fail criteria.
  • Used to check how the material will resist corrosion in real working conditions.
  • The test procedure is followed to check the effectiveness of the production procedure such as the quality of surface coating of metals.

Salt spray testing machine

The salt spray machine comprises a chamber where salt water solution i.e. NaCl is atomized and spread uniformly with the help of a spray nozzle using pressurized air. This procedure creates a highly corrosive environment inside and generates a salt water fog or mist so that the test samples can be exposed to the salty environment easily. The size and capacity of the salt spray chambers vary as per requirement of the customers.

The manufacturing of the machine, the testing procedure as well the testing parameters that are utilized are completely standardized and developed after following the guidelines of national and international standard test methods such as ISO 9227 and ASTM B117. The standards describe the entire information for carrying out the test, testing constraints such as air pressure, salt solution, the temperature of the chamber, the concentration of the salt solution, pH of the salt solution, preparation procedure of salt solution and many more.

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