Stainless steel has a far greater corrosion and heat resistance than normal mild steel. It is used for applications requiring high corrosion resistance, heat resistance or extended life. It is an increasingly popular construction material with its whole life cost benefits contributing to towards more sustainable development.
Stainless Steel is a group of steels containing a minimum of 10.5% chromium where corrosion resistance is determined by the amount of chromium and the addition of alloys such as nickel, manganese and molybdenum.
The formation of a stable, passive oxide film on the surface provides stainless steel with a corrosion protection layer. The film forms rapidly by the alloy elements in the steel, mainly chromium, nickel and molybdenum, reacting with water and air. Stainless steel is available in several different grades, each grade containing varying percentages of alloys used to provide the material with physical properties such as strength, corrosion resistance, welding, machining, etc.
The selection of the correct grade of stainless steel must take account of the following features:
- The environment
- Structural requirements
- Life of structure
- Surface finish
Factors, which may influence the selection within an environment, are temperature, pollutants, humidity and presence of chloride ions.
Civil Engineering and Geotechnical
Stainless UK Ltd stock the two main grades of stainless steel used in construction.
Grade 304 (1.4301) is the grade most often used for corrosion resistant reinforcement, suitable for most atmospheric and concrete covered environments.
Grade 316 (1.4436) has a higher molybdenum and nickel content than 304 (1.4301). It is more expensive but also has higher corrosion resistance and is the recommended grade for marine and corrosive environments.
Although the chemical composition and corrosion resistance are different, the physical properties of the 2 grades are similar.
Stainless steel continues to grow in popularity as a construction material with more contractors and engineers appreciating the materials benefits in terms of whole life costing and contribution towards more sustainable development.
Heat Resistant and Corrosion Resistant Steel and Products
In addition to Grades 304 and 316, Stainless UK can supply the following grades for heat and corrosion resistant applications requiring stainless steel products to function at temperatures up to 1200°C or corrosive environments.
Austenitic Stainless Steel
Grade 310 (1.4845) is a heat resisting steel with excellent resistance to corrosion and oxidisation at high temperatures.
Grade 321 (1.4541) is stabalised with titanium to prevent weld decay. It combines good resistance to oxidisation with strength at elevated temperatures.
Duplex and Super Duplex
Lean Duplex S32304 (1.4362) - A 23% chrome and 4% nickel duplex stainless steel. Lean duplex has similar corrosion properties to Grade 316L and mechanical properties similar to austenitic grades 304 and 316.
F51 Duplex S31803 (1.4462) - An austenitic / ferritic duplex with 22% chrome. Good general corrosion and stress corrosion resistance
F53 Super Duplex S32750 (1.4410) - An austenitic / ferritic super duplex with 25% chrome. Good strength and ductility with a high resistance to marine corrosion.
F55 Super Duplex S32760 (1.4501) - An austenitic / ferritic super duplex with 25% chrome and 0.75% tungsten and copper. A high corrosion resistance with good strength and ductility
Alloy 600 - A nickel chromium alloy with good oxsidation resistance at high temperatures. Good resistance in carburizing and chloride containing environments.
Alloy 601 - A chromium heat resisting alloy with excellent performance up to 1200° C with good strength and toughness at extended high temperatures.
Alloy 625 - A nickel, chromium, molybdenum alloy with high strength at elevated temperature combined with excellent corrosion resistance.
Alloy 718 - A precipitation hardening nickel chrome alloy. Good strength properties from below 0° C to over 760° C, corrosion resistance in a range of environments and choride stress corrosion.
Alloy 800 - A austenitic nickel-iron-chrome alloy. Excellent creep strength at above 700° C. Good resistance to reducing, oxidising and nitriding atmospheres.
Alloy 825 - A titanium stabilised fully austenitic nickel-iron-chrome alloy. Good resistance to stress cracking and resistance to pitting, crevice corrosion, oxidising and non oxidising hot acids.
Alloy C276 - A nickel-molybdenum-chrome superalloy with the addition of tungsten. Widely used in the most severe environments. Excellent corrosion resistance in reducing environments with resistance to pitting and stress corrosion.
Alloy X - A nickel-chrome-iron-molybdemun alloy. Good resistance to oxidation and high temperature strength. Exceptionaly resistant to stress corrosion cracking in petrochemical
The initial costs of using stainless steel are high but they can be cheap when compared to the costs that can be incurred due to premature failure or need for repair or replacement due to corrosion.
The greatly extended life of stainless steel reduces the need to repair and replace structures so saving on future energy consumption. At the end of its life stainless steel is 100% recyclable.