Seawater will become one of the most important sources of drinking water.

Water is man's most important resource.

Due to the expansion of population and the increase of water consumption, fresh water resources are continuously decreasing, and the water shortage problem in many parts of the world is increasingly prominent.

Some predict that the 19th century will be dominated by coal, the 20th by oil and the 21st by water.

Two-thirds of the earth's surface is covered by water, but 97% of its water reserves are seawater and brackish water. Desalination has to be desalinated to make use of seawater.

But only 1% of the world's drinking water is now desalinated.

More than 12,500 desalination plants have been built in more than 120 countries.

47% of the world's desalination capacity is concentrated in the Middle East.

With more than a quarter of the world's population living within 25km of coastlines, seawater will become one of the most important sources of drinking water.

Why choose stainless steel seawater desalination method there are two main methods: heat method and membrane method.

The thermal method includes multistage flash distillation (MSF) and multieffect distillation (MED).

Membrane methods include repeated penetration (RO) and electrodialysis/repeated electrodialysis (ED/EDR).

Stainless steel is used in various desalination projects due to its corrosion resistance.

All desalination methods are the same process.

The seawater is divided into two parts, one for treatment and the other for concentration.

The salt concentration of the treated seawater decreased, while the salinity of the concentrated seawater was much higher than that of the original seawater.

The equipment materials used in the desalination process shall be corrosion resistant.

Material selection and design principles depend on the material's service environment.

Stainless steel makes an ideal material because of its corrosion resistance and durability.

There are more than 200 kinds of stainless steel, only some of which can be used in seawater desalination projects.

The stainless steel used in desalination projects requires good corrosion resistance in a variety of complex environments.

Austenitic stainless steel 316L and 317 are the main materials used in seawater desalination equipment.

316L can withstand corrosion in the Marine environment, but long-term immersion in seawater can lead to pitting and crevice corrosion.

The pitting of stainless steel in the seawater desalination equipment for the treatment of hot concentrated seawater in the environment containing chlorine ions is very noteworthy.

Most modern multistage flash desalination (MSF) devices do not use 316L stainless steel, although hot seawater hypoxia reduces the tendency of a little corrosion, and 316L stainless steel is the traditional material for evaporators.

The reason why duplex stainless steel has become an important material for seawater desalination is that it has excellent corrosion resistance, especially stress corrosion cracking.

Stress corrosion cracking is a kind of corrosion method that causes sudden failure of materials under certain temperature, corrosion environment and tensile stress.

The strength of duplex stainless steel is twice that of austenitic stainless steel, especially its excellent mechanical properties can reduce the cost of materials.

Duplex stainless steel is also an excellent engineering material.

The 2205 duplex stainless steel has been applied to the shell of the evaporator of the multistage flash evaporation (MSF) desalination plant.

The Libyan Melittah desalination plant, built in 2004, and the Algerian Skikda desalination plant, built in 2005, both use 2205 duplex stainless steel.

FISIA, an Italian plant that makes desalination plants, USES duplex stainless steel as the engineering material.

Construction cases are Taweelah B expansion project in Abu dhabi, Jebel Ali L project in dubai and Ras Abu Fontas project in Qatar.

These projects adopt the concept of "full duplex", with 2205 duplex stainless steel used in harsh environments and energy-saving duplex stainless steel used in slightly weaker corrosive environments.

Economical duplex stainless steel is an economical duplex stainless steel with lower nickel and molybdenum content than 2205 duplex stainless steel.

Corrosion resistance is similar to 316L.

Due to its high mechanical properties, energy-saving duplex stainless steel can reduce the equipment weight by 50% compared with austenitic stainless steel, thus saving 35%~40% of the cost.

The "full duplex" concept has been applied to multiple effect distillation (MED) desalination plants (see figure 1), the first of which was built by Sidem at Sharjah, uae, using 2205 and 2304 duplex stainless steel.

Experimental data from 27 seawater desalination plants using SWRO have confirmed that if 316L and 317L of high-pressure pipe materials are used, they do not have sufficient corrosion resistance, and t