2. The nuances of stainless steel

1. The corrosion resistance of stainless steels

• 304 : It is the basic austenitic stainless steel. It is particularly easy to solder and also has good corrosion resistance at room temperature. If this type of steel is kept for a certain time in the critical temperature range between 450° and 850° C., it risks the intercrystalline precipitation of chromium carbide and therefore intergranular corrosion.
• 304L : This is a variant of 304 containing less than 0.03% C, which guarantees a very low formation of chromium carbide if it is maintained for a long time in the critical temperature range and which has a very low risk of intergranular corrosion.
  
• 321 : This type of steel includes 304 elements to which a certain amount of titanium has been added to prevent the formation of chromium carbide. It therefore does not involve any phenomenon of intergranular corrosion and it is particularly recommended in case of prolonged use in the critical temperature range. Good cutting resistance up to about 800°C.
  
• 316 : It contains an addition of 2-3% molybdenum which makes it particularly resistant to chemical agents that have a reducing action. In the critical temperature range, it also presents the risk of chromium carbide precipitation.
  
• 316L: Thanks to a carbon content of less than 0.03%, the formation of chromium carbide is very low and it has good resistance to intercrystalline corrosion.
  
• 316Ti: The addition of titanium also prevents the formation of chromium carbide and therefore makes this material particularly suitable for prolonged use in the critical temperature range. It resists the formation of cuts up to a temperature greater than 800°C.
  
• 904L: 904L is a stainless steel intended to be used under severe corrosion conditions mainly applied in offshore fields, oil refineries, chemical and petrochemical industries. It is characterized by the following properties:
  + Very good resistance to attacks in acidic environments such as sulfuric, phosphoric and acetic acids.
  + Very good resistance to pitting corrosion in neutral solutions containing chlorine.
  + Resistance to intersticial corrosion that is much higher than that of type 304 and 316L steels.
  + Very good resistance to corrosion under stress.
  good solderability.
  
• Alloy 800 (Inconel 800*): Refractory alloy with a high nickel and chrome content. It has a high resistance to the formation of cuts up to 1100°C, a high breaking load and good corrosion resistance at high temperatures.
  
• Alloy 825 (Inconel 825): Nickel-chrome alloy that is resistant to corrosion at high temperature, in particular from sulfuric acid, as well as to intergranular corrosion.
  
• Alloy 600 (Inconel 600*): It is the best quality refractory alloy. It resists the formation of cuts up to 1200°C, has a high breaking load and has excellent corrosion resistance at high temperatures.
  
• Alloy 400 (Monel 400*): Nickel-copper alloy resistant to the corrosion of seawater and sulfuric, hydrochloric and phosphoric acids. It maintains good mechanical strength and good toughness up to temperatures of 400°C.
  

2. Normative table of nuances