Are you involved in the manufacture of materials and coatings that will be exposed to corrosive environmental elements during use? Have you heard of the term “salt spray testing”, but don’t fully understand what it means and its importance when it comes to guaranteeing the quality, reliability and durability of your products during their application in the field?
To find more about salt corrosion testing, and get comprehensive answers to the above questions, please read more below.
What Is Salt Corrosion Testing?
Also referred to as salt fog testing, salt corrosion testing can be defined as an accelerated corrosion test designed to measure the comparative corrosion resistance of materials and coatings exposed to a salt fog or salt spray at high temperatures.
To study the effects of corrosive elements on various metals and surface coatings, samples are exposed to an aerosol or mist of fine salt particles, intended to mimic real-world natural weather conditions, in a controlled lab environment.
Once the test is complete, after a stipulated amount of time, the damage to the sample is assessed visually and compared to other samples. Afterwards, the outcome is reported as equivalent “hours at” exposure.
The Importance Of Salt Corrosion Testing
Salt corrosion testing is primarily used to evaluate the corrosion resistance of finishes and coatings on metal surfaces. The effect of different environmental elements, including temperature and humidity, on the ability of a coating to resist corrosion, can be evaluated using this testing method. Salt corrosion testing can also be used to compare the performance/effectiveness of various finishes and coatings.
These tests can also be used by product manufacturers to demonstrate compliance with relevant environmental guidelines and regulations.
Different Methods Of Corrosion Spray Testing
The procedures for conducting a salt corrosion test are defined under the IEC 60068-2-52 standard. The parameters to be assessed, testing conditions and type of salt to be used in testing are all specified by this standard.
Other international standards are designed to ensure the undertaking of standardised spray tests by specifying the calibration method using corrosion reference specimens including ASTM B117, ISO 9227, ASTM G85 and JIS Z 2371 among others.
It is important to note that the reliability and reproducibility of the outcomes/results of corrosion tests, including the salt spray test, are made possible by lab accreditation. Simply put, the results obtained on the corrosion resistance of coatings and materials by different labs can be compared thanks to the standardised testing facilitated by various lab accreditation standards.
Some of the different salt corrosion testing methods include:
Copper Accelerated Acetic Acid Salt Spray (CASS)
The corrosion resistance of polymer, cadmium and zinc coatings is normally tested using the Copper Accelerated Acetic Acid Salt Spray test. With the addition of another dehydrate and glacial acetic acid, this testing method can also be used to assess the effect of an environment on the surface of a metal.
Acetic Acid Salt Spray (AASS)
The effect of an environment on the surface of a metal can also be investigated using the Acetic Acid Salt Spray test. The corrosive attack is enhanced with the addition of Acetic Acid in this test. This also results in a more aggressive and non-uniform corrosion effect. The test, which is conducted at 50ºC, is primarily used for testing ferrous metals including, iron, steel and nickel.
Neutral Salt Spray (NSS)
The impact of an environment on the surface of a metal, without affecting any decorative or protective properties is evaluated using the NSS (Neutral Salt Spray) method. This method results in slow and uniform corrosion. Conducted at 35ºC, this testing method is used on a variety of ferrous and non-ferrous metals including, titanium, zinc, copper, magnesium and aluminium alloys.
Salt corrosion testing is used to assess the corrosion resistance of various coatings and finishes on metal surfaces. To ensure standardised results even when testing is done in different labs, the procedures used in conducting salt spray tests are set out under the IEC 60068-2-52 standard.
Compliance Engineering offers Salt Spray Testing services compliant with a variety of international standards. To learn more, please get in touch with our team of experts!