How is the corrosion resistance of the 2205 duplex stainless steel pipe?

2205 duplex stainless steel pipe has extremely excellent corrosion resistance, and performs outstandingly in various corrosive environments. The following introduces its specific properties such as composition and resistance to pitting corrosion, as well as its performance in different environments: 

The contribution of alloy composition to corrosion resistance

Chromium (Cr) element: The chromium content in 2205 duplex stainless steel tubes is around 22%. Chromium is the key element for enhancing the corrosion resistance of stainless steel. It can form a dense chromium oxide protective film on the metal surface, which acts as a passivation layer. This layer can prevent oxygen, water, and other corrosive media from coming into contact with the metal substrate, thereby effectively slowing down the corrosion process. 

Molybdenum (Mo) element: The molybdenum content is approximately 3%. The addition of molybdenum can enhance the corrosion resistance of stainless steel in reducing media, especially playing an important role in resisting the corrosion of chloride ions. It can improve the stability and repair ability of the passivation film, making stainless steel less prone to pitting and crevice corrosion in corrosive media containing chloride ions, etc. 

Nitrogen (N) element: The nitrogen content is generally around 0.18%. Nitrogen can enhance the strength and corrosion resistance of stainless steel. In terms of corrosion resistance, it can strengthen the performance of the passivation film, improve the corrosion resistance of stainless steel in acidic environments, and also help to inhibit the occurrence of intergranular corrosion. 

Specific corrosion resistance performance

Corrosion resistance to pitting: The 2205 duplex stainless steel pipe exhibits excellent pitting resistance. Its pitting resistance equivalent (PREN) is relatively high, typically above 32. A higher pitting resistance equivalent indicates a stronger ability of the material to resist pitting. In media prone to pitting such as those containing chloride ions, it can effectively prevent the occurrence of pitting and is less likely to develop local corrosion pits compared to some ordinary stainless steels. 

Resistance to crevice corrosion: Due to the reasonable composition of its alloy and the dual-phase structure, 2205 duplex stainless steel pipes can effectively resist crevice corrosion in environments with crevices, such as at pipe connections and at the contact points between gaskets and pipes. Its passivation film can still maintain a certain stability in the oxygen-deficient environment within the crevices, thereby slowing down the corrosion rate. 

Intergranular corrosion resistance: The 2205 duplex stainless steel pipe has a low carbon content, and the presence of nitrogen elements helps to inhibit the precipitation of carbides, thereby reducing the formation of chromium-poor zones at the grain boundaries, making it have excellent intergranular corrosion resistance. During welding and other heat processing operations, it can also maintain the corrosion resistance of the grain boundaries well, reducing the risk of intergranular corrosion. 

Stress corrosion cracking resistance: The reasonable proportion of austenite and ferrite phases in the duplex stainless steel ensures high strength and good toughness. Under stress conditions, it can effectively resist stress corrosion cracking. Compared with single-phase austenitic stainless steel, 2205 duplex stainless steel pipes have lower sensitivity to stress corrosion cracking in some high-temperature and high-pressure environments with chloride ions. 

Performance in Different Corrosive Environments

In marine environment: The marine environment contains a large amount of chloride ions, which have a strong corrosive effect on metal materials. The 2205 duplex stainless steel pipe, with its excellent resistance to chloride ion corrosion, is widely used in marine engineering fields such as seawater desalination equipment and offshore oil platform pipelines. It can maintain good corrosion resistance in the marine environment for a long time, reducing the maintenance and replacement costs caused by corrosion. 

In the chemical industry: In chemical production, one often comes into contact with various corrosive media such as acids, bases, and salts. The 2205 duplex stainless steel pipe has good tolerance to many common corrosive media. For example, in some chemical processes containing acidic media like sulfuric acid and hydrochloric acid, it can operate stably and is not easily corroded, ensuring the safety and stable operation of chemical equipment. 

In the food processing environment: In the food processing industry, equipment needs to frequently come into contact with water, salt solutions, organic acids, etc. The 2205 duplex stainless steel pipe has excellent corrosion resistance and hygiene properties, can resist the corrosion of these substances, and will not cause pollution to the food, meeting the strict requirements of the food processing industry.