Which steel is good for corrosion resistance and high pressure conditions?

 

 

 

Which steel is good for corrosion resistance and high pressure conditions?

Check the features of different industrial steel

Stainless steel is used in many industrial and applications for strength, lifespan, corrosion resistance and for cost efficiency. There are different grades of stainless steels, all of them having more than 11% of chromium in their composition. To increase the strength and corrosion resistance, molybdenum, nickel and other elements are added in various amounts in various grades of steels. The grades are determined by international standards and have different mechanical properties. There are engineered combinations of grades for specific corrosion resistance as well.

Corrosion resistance material chart

  • 1

    Stainless steel

    More than 11% of chromium

  • 2

    Monel 400 or alloy 400

    Suitable for acidic systems and in chemical processing plants

  • 3

    Alloy c276

    Contains molybdenum nickel and chromium

  • 4

    Alloy 625

    Resistant to hydrochloric and nitric acids

  • 5

    Super Duplex

    High crevice and pitting corrosion resistance

  • 6

    Alloy 825

    Resistant to sulfuric and phosphoric acids

One of the most widely used engineered combinations is the use of SS products of 316 or 316L material with the alloy grades of 254, 904L, 825 and copper alloy UNS C69100. This allows for varying corrosive factors in varying parts of the piping system and keeps the system intact from corrosion. This is useful in systems that need to keep the cost low, gain low galvanic corrosion, high pitting and crevice corrosion and resistance to localized corrosion.

 

Next in are the titanium alloyed stainless steel grades. The addition of titanium ranges from trace amounts to commercially pure titanium. In case of the steel, the addition of titanium improves strength and corrosion resistance but these types of alloys are costlier than the other types because of the high cost of the raw material. These are used in armor plating, missile components, naval ships and in aircraft.

 

The Monel 400 or alloy 400 is corrosion resistant especially against hydrofluoric acid. This is handy when using the steel components on acidic systems and in chemical processing plants. The strength of the material is high and therefore can withstand high pressures as well. The mechanical properties remain the same even at subzero temperatures. For example, the class 2500 can withstand 173.0 bars of pressure at 475 degree Celsius. This type of steel is used in electric and electronic components, crude petroleum still, heaters, boilers and heat exchangers.

 

Alloy c276 is another grade that contains molybdenum nickel and chromium. It has 15% molybdenum, 14% chromium, 3% tungsten, and other elements in smaller amounts such as sulfur, carbon, silicon, vanadium, cobalt, and manganese. With this combination, it gets high ductility, oxidation and reduction resistance, high toughness and strength. This material is also resistant to pitting and crevice corrosion. It is used mostly in sour gas applications.

 

The nickel alloys such as the 825 and 625 are also used in applications that require high corrosion resistance and pressure ratings. These are called Incoloy and are used in acid production, pollution control, gas recovery and in nuclear fuel processing. The 625 is particularly resistant to hydrochloric acid and nitric acids and the 825 is particularly resistant to sulfuric and phosphoric acids.

 

Super duplex grades of stainless steel are also highly corrosion resistant and are of high pressure capacities. The alloy 2507 in particular has a high yield and tensile strength. The composition contains molybdenum, nickel, chromium, manganese and nitrogen. So they have high crevice and pitting corrosion resistance. Due to the strength and pressure rating, these are used in vessels, pipes and in heat exchangers as well. Some specifications can withstand up to 1040 bars of pressure.

 

Super austenitic alloys such as the 6-moly alloys so show high corrosion resistance to chloride ion pitting and crevice corrosion. These are used mostly in sour gas applications as well. They contain carbon, chromium, copper, nickel, sulfur silicon and other elements. They are used in seawater, brackish water and in high chloride ion rich environments.

 

Perhaps the most cost efficient type of corrosion resistant steel is the 316 steel. It has 2-3% molybdenum added to the chromium nickel steel and it improves corrosion resistance greatly. The variations can go up to 4134 bars of pressure. Therefore these are suitable for high pressure and highly corrosive applications such as tubing, heat exchangers, coastal balustrading, chemical equipment, food processing plant components and many others.

 

Although there are differences in each of these grades of stainless steel material grades, they are all suitable for specific applications. It is the appropriate and integrated usage that will bring value to the right product in the right application.

Steel for seawater, brackish water and in high chloride ion rich environments.