Testing for corrosion is done to determine a material’s or coating’s resistance to the corrosion process, which is brought on naturally by a chemical or electrochemical response to the aggression of oxidising agents like, for instance, atmospheric oxygen, moisture, gas, and corrosive solutions. This process causes the material that is prone to oxidation to gradually deteriorate and lose its properties (this is evident in all situations when a metal surface rusts). Manufacturers can learn how corrosion affects their products and which coatings or materials could be best suitable for the application by using a corrosion test chamber, also known as a salt-spray test chamber.
A corrosion test chamber may perform a wide range of salt spray tests; which one is selected depends on the application area, the type, and the dimensions of the product being tested.
The primary tests that need to be run are:
When a product is put through a dry corrosion test, it is subjected to cycles of salt spraying, followed by low humidity drying phases (during which tiny salt deposits unleash a powerful corrosive attack).
Test with continuous salt spray in which the product is continually exposed to the salt spray phase and, consequently, to corrosion until the end of the test period.
Salt spray alternate allows for alternating between salt spray and standby phases.
Salt spray testing is a method of testing the corrosion resistance of coatings and materials used in the manufacture of products such as fasteners. Manufacturers can gain a better understanding of how corrosion affects their products and which coatings or materials might be most appropriate for a given application by using a corrosion test chamber, sometimes referred to as a salt-spray test chamber.
Salt spray testing is commonly used to quickly compare expected and actual corrosion resistance. In fact, there is only a weak correlation between test coating life and actual life expectancy. This is because corrosion is not a simple process and many external factors affect it.
This is why applying the salt spray test to a sample to obtain a pass or fail rating and comparing the results to expected values yields the best results. This is frequently done in quality control jobs or to gauge how well a certain production process is working.
Because it is quick, repeatable, and reasonably priced, salt spray testing has long been a typical corrosion testing technique. The first test of this kind to be accepted globally was ISO 9227, which was developed in 1939. Neutral salt spray tests are conducted in accordance with the current international test standard (2012), and findings are often published in accordance with other pertinent standards.
In a test chamber that is typically closed, the salt spray test is conducted. Through a spray nozzle, a saline solution is administered to the sample. This thick saltwater fog mimics the effects of caustic experiments. Depending on how well the product resists corrosion, assess the oxidation appearance over time. The longer it takes for oxidizing to manifest, the more resistant the product is. Test duration for some coatings can be as long as 1,000 hours or more.
Why use it?
A material’s corrosion resistance results in a salt spray test can help determine whether a particular fastener is durable and strong enough for your needs.
A salt spray test is a laboratory simulation of a corrosive saline environment. It is used as a expanded manner of checking out the capacity of floor coatings to face up to atmospheric corrosion. One of the earliest testing techniques utilised in the HVAC-R coatings industry is known as salt fog testing. For this reason, it is frequently brought up when choosing HVAC-R coatings.
Salt spray checking out is used as a stand-on for corrosion resistance, it takes a look at and additionally as an issue of ISO 12944-9 (formerly referred to as ISO 20340). The ASTM B-117-compliant salt spray method is used consistently for each check.
Typically, this takes a look at is carried out according to the ASTM B117 or ISO 9227 checking-out procedures. The samples being compared are positioned in an enclosed chamber after which uncovered to a thick metallic fog that simulates significantly corrosive conditions. They take a look at employing a sodium chloride answer with a pH variety of 6.5 to 7.2. This takes a look at normally lasts eight to 3,000 hours. Though, as formerly stated, there are lots of different corrosion checks, the salt spray takes a look at could be very common. However, professionals are divided on how carefully it displays real-existence conditions. Some professionals, for example, query the take a look at suitability as it does now no longer contain publicity to salt chemicals.
How does a salt spray test chamber work?
Chemical vapours that induce corrosion play a part in the metal industries since the material is subjected to a variety of environmental conditions. Testing the materials to determine their quality is therefore crucial. The three walls of this salt chamber will be completely insulated. It uses compressed air pressure and includes various features including an integrated control panel for exact parameters, a sturdy and corrosion-free body, among others. Therefore, you must take a few essential actions in order to examine the sample.
- In a chamber of this testing device, a saltwater solution is automatically vaporised by using air pressure.
- It will cause a thick water fog to develop inside the chamber. The rate of corrosion that the specimen can endure will be seen once it has been placed inside the chamber.
- It is possible to code crucial factors like temperature and time.
- To determine the surface’s capacity for resistance, testing can be carried out using a pure water solution.
- The test’s rounds and cycles are determined by the testing’s needs and specifications.
Thus you can see how a salt spray tester or a corrosion test chamber works.