Material Selection for Filters in Seawater Desalination Systems: Case Analysis of Pitting Corrosion Resistance of S32760 Super Duplex Stainless Steel

In seawater desalination systems, the selection of FILTER MATERIALS is of crucial importance as it directly relates to the stability and service life of the systems. As a high-performance material, S32760 super duplex stainless steel has gradually become an ideal choice for seawater desalination filters due to its outstanding pitting corrosion resistance. This article will explore the application advantages of S32760 super duplex stainless steel in seawater desalination systems through comparative analysis and elaborate on it in detail with practical cases.

I. Requirements for Filter Materials in Seawater Desalination Systems

SEAWATER DESALINATION SYSTEMS FACE EXTREME CORROSIVE ENVIRONMENTS. The high content of chloride ions, large temperature variations, and complex microbial environments pose extremely high requirements for filter materials. Ideal filter materials need to possess the following characteristics:

• Pitting corrosion resistance: Chloride ions in seawater can destroy the passive film of stainless steel, leading to the occurrence of pitting corrosion. Therefore, filter materials must have high pitting corrosion resistance.

• High strength: During the seawater desalination process, filters need to withstand relatively high pressures and water flow impacts, so the materials must have sufficient mechanical strength.

• Good welding performance: In the actual installation and maintenance processes, welding is a common connection method. Filter materials need to have good welding performance to ensure the corrosion resistance and strength of welded parts.

• Economy: On the premise of meeting performance requirements, cost is also an important consideration factor. Choosing materials with high cost performance can reduce the construction and operation costs of the system.

II. Prformance Characteristics of S32760 Super Duplex Stainless Steel

S32760 SUPER DUPLEX STAINLESS STEEL IS A HIGH-STRENGTH AND HIGHLY CORROSION-RESISTANT MATERIAL. Its main components include 25% - 27% chromium, 7% - 8% nickel, 3.5% - 4.5% molybdenum, and 0.25% - 0.35% nitrogen. These components endow S32760 with the following excellent properties:

• Outstanding pitting corrosion resistance: The pitting corrosion resistance equivalent (PREN) value of S32760 is as high as above 40, much higher than that of ordinary stainless steel (for example, the PREN value of 316L is about 25). In seawater with a high concentration of chloride ions, S32760 can effectively resist the occurrence of pitting corrosion.

• High strength: The yield strength and tensile strength of S32760 are respectively twice those of ordinary austenitic stainless steel and can withstand higher pressures and mechanical loads.

• Good welding performance: S32760 is not prone to cracking during the welding process, and the corrosion resistance and strength of the welded parts are equivalent to those of the base metal.

• Resistance to stress corrosion cracking: In a chlorine-containing environment, S32760 exhibits excellent resistance to stress corrosion cracking, which is particularly important for components that bear stress for a long time in seawater desalination systems.

III. Comparison between S32760 and Other Common Materials

It can be seen from the above table that S32760 super duplex stainless steel is superior to 316L austenitic stainless steel and 2205 duplex stainless steel in terms of pitting corrosion resistance, strength, and resistance to stress corrosion cracking, and its economy has an advantage compared to titanium alloy.

IV. Case Analysis of Pitting Corrosion Resistance of S32760 Super Duplex Stainless Steel

Case Background
During the operation of a seawater desalination plant, it was found that the pitting corrosion problem of its FILTERS seriously affected the normal operation of the system. After investigation, it was found that the original filters were made of 316L austenitic stainless steel. Due to its insufficient pitting corrosion resistance, pitting pits quickly appeared in seawater with a high concentration of chloride ions, resulting in filter leakage and a decline in efficiency.

Solution
In order to improve the pitting corrosion resistance of the FILTERS, the plant decided to change the FILTER materials and choose S32760 super duplex stainless steel. The high PREN value and excellent pitting corrosion resistance of S32760 enable it to effectively resist the corrosion of chloride ions in seawater.

Implementation Process
• Material selection: According to the specific working conditions of the seawater desalination system, S32760 super duplex stainless steel was selected as the main material for the filters.
• Welding process: Since S32760 has good welding performance, the standard welding process was adopted to assemble the filters.
• Installation and commissioning: The newly replaced S32760 filters were installed in the system and underwent strict commissioning to ensure their stable operation.

Effect Evaluation

AFTER A PERIOD OF OPERATION, THE S32760 SUPER DUPLEX STAINLESS STEEL FILTERS EXHIBITED EXCELLENT PITTING CORROSION RESISTANCE. Compared with the previous 316L filters, the S32760 filters did not show obvious pitting corrosion phenomena under the same working conditions. The operation efficiency of the system was significantly improved, and the maintenance cost was greatly reduced.

V. Conclusion
S32760 super duplex stainless steel has become an ideal material for FILTERS in seawater desalination systems by virtue of its outstanding pitting corrosion resistance, high strength, and good welding performance. Through the analysis of practical cases, we can see that S32760 can effectively resist the occurrence of pitting corrosion in seawater with a high concentration of chloride ions and significantly improve the stability and service life of the system. When selecting filter materials for seawater desalination systems, S32760 super duplex stainless steel is undoubtedly a high-performance material worthy of priority consideration.