salt spray
Some applications, e.g., in sea transport or generally in contact with sea water, require corrosion resistance to salt water. The most common tests in this area include neutral salt spray (NSS) tests, based on standards: ISO 9227 or ASTM B117. The part to be tested is exposed to salt spray in a chamber made for this purpose, for a period of time determined by the customer, with the possibility of continuously verifying the condition of the part. The test can be performed on the materials themselves (e.g., permanent magnet or another metallic material) as well as on finished parts and products.
surface protection of magnets
If there is a risk of using magnets in an environment with the presence of salt water, the magnets should be provided with additional surface protection. A neutral salt spray test of permanent magnets pursuant to EN ISO 9227 is primarily designed to test the resistance of their surface protection. Our laboratory tested a large majority of commercially available protection methods for permanent magnets and can recommend the most suitable one for a given application.
weld corrosion
Weld corrosion in a salt spray environment is often referred to as corrosion attacks on welded joints. Salt spray contains chlorides and other substances that can react with metal surfaces, especially welded joints, causing corrosion. This kind of corrosion process is called chloride-induced stress corrosion cracking (CCSCC). Welded joints are often more susceptible to corrosion attack because of changes in the microstructure of the metal and the formation of heat-affected zones around the welds during welding, and are therefore usually more susceptible to various forms of corrosion damage. Corrosive salt spray can induce corrosion reactions at these sites, often through processes such as undercoating corrosion, where chlorides in the salt spray can enter microscopic cracks in the welded joint and induce corrosion reactions that gradually weaken the material and can lead to failures.
galvanic corrosion of metals
Galvanic corrosion is a process in which metals are damaged due to electrochemical reactions between different metals in an environment with moisture or electrolytes, such as corrosive salt spray. Corrosion occurs when two metals with different electrical potentials are connected and are in contact through an electrically conductive medium. When these metals are combined, one becomes the cathode and the other the anode in an electrochemical reaction, resulting in the transfer of electrons and the decomposition of one metal. This process is particularly problematic in environments with high humidity, such as seawater environments or environments with chemicals that serve as electrolytes. Galvanic corrosion can lead to severe degradation of metals, causing weakening, structural failure, and ultimately failure. In order to prevent galvanic corrosion, it is important to separate the different metals from each other, use protective coatings or insulating materials, and use corrosion-resistant materials. For example, when aluminium and steel are combined in an electrolyte environment, the aluminium will protect the steel and corrode itself. In the case below, the electrolyte (salt solution) flows through the separation layer and corrodes the aluminium.
we perform neutral salt spray tests
- pursuant to EN ISO 9227 or ASTM B117
- chamber size 800x550x650 mm
- length and method of test evaluation based on individual specification
Jan Kratochvil ml.
