Salt spray corrosion testing: Ensuring durability in marine pipeline systems

Haihao Group has been actively involved in numerous marine pipeline projects, including subsea pipelines, large ship piping systems, and offshore drilling platforms. Many of these projects require that the piping system products undergo rigorous salt spray testing to assess their resistance to corrosion in marine environments.

Salt spray corrosion mechanism corrosion of metal materials occurs predominantly in atmospheric environments, which contain corrosive components such as oxygen, moisture, and pollutants. Salt spray corrosion is a particularly aggressive form of atmospheric corrosion. The primary mechanism involves a conductive salt solution penetrating the metal surface, leading to an electrochemical reaction. This reaction forms a “low-potential metal-electrolyte-high-potential impurity” micro-galvanic cell, where electrons transfer, causing the metal (anode) to dissolve and produce corrosion byproducts.

Comparison before and after salt spray corrosion testing

The key factor in salt spray corrosion is the chloride ion (Cl-), which is highly penetrative, easily passing through the metal’s oxide layer to reach the metal’s core. Chloride ions disrupt the protective oxide film on the metal surface, accelerating corrosion. Chlorides also have low hydration energy, allowing them to be readily adsorbed onto the metal surface, displacing the oxygen from the oxide layer and initiating metal degradation.

Salt spray testing methods salt spray testing is an accelerated method for evaluating the corrosion resistance of materials in a controlled environment. A salt solution, typically sodium chloride, is atomized and sprayed in a closed, heated chamber where the test sample is placed. This method significantly accelerates the corrosion process, allowing manufacturers to observe the effects in just a few days or hours, as opposed to years in a natural environment.

The primary types of salt spray tests include:

1.Neutral Salt Spray Test (NSS) – the most common test, utilizing a 5% sodium chloride solution with a neutral pH of 6-7.

2.Acetic Acid Salt Spray Test (AASS) – a more aggressive test, where acetic acid is added to lower the pH to around 3, making the salt solution more corrosive.

3.Copper-Accelerated Acetic Acid Salt Spray Test (CASS) – this is an even more rapid corrosion test that uses copper salts to strongly induce corrosion.

4.Cyclic Salt Spray Test – this method alternates between exposure to salt spray and drying periods to more closely simulate natural corrosion conditions.

These tests help ensure that Haihao Group’s products can withstand the harsh conditions often found in marine environments, providing durable and reliable solutions for pipeline systems in marine and offshore projects.