Depending on the different industrial applications, it is essential to properly select the most suitable stainless steel to guarantee performance, durability and safety.
Among the most used alloys, we find the austenitic steels such as 304/304L, 316/316L and 317L that, even if they seem similar, each of them has got specific features that make them more suitable in certain contexts than in other ones.
Provided below is a brief, but exhaustive examination of the three kinds
When selecting the material the guiding criteria is that the most the application must be deployed in a critical environment, the most is necessary to choose from those that offer higher performance.
AISI 304 AND 304L: versatile, cheap and suitable for standard applications
AISI 304 is the most used among stainless steels for its versatility and its excellent workability cost ratio since it guarantees a good resistance to corrosion in atmospheric and less aggressive environments; for these reasons it is the right balance between costs and features (workability and corrosion resistance).
The version AISI 304L (low carbon), with a reduced percentage of carbon, ensures a better resistance to the intergranular corrosion, especially after welding.
Usual applications:
- Food industry (tools and work surface)
- Dry internal environments or with a controlled level of humidity
- Architecture and furniture (tables, shelves and interior cladding)
- Electrical appliance
- Industrial plants not exposed to aggressive agents
Therefore, this kind of steel is particularly preferred for standard applications where there aren’t chlorides or particularly corrosive substances.
AISI 316 AND 316L: a moderate choice
Moving up to steel grades, there is the AISI 316 version that is different from 304L due to molybdenum addition significantly adding its corrosion resistance especially in case of chlorides, high levels of humidity and in marine contexts and if it is localized (pitting and crevice corrosion).
Also in this case, the 316L option ensures a better resistance after welding.
Usual applications
- Naval and offshore field
- Chemical and pharmaceutical industry (tanks and pipes)
- Food industry when salts are present (salt solutions, fish processing and cold cuts)
- Components and structures exposed to weather elements for example in the marine environment (railings, stairs and walkways) and bad weather (structures exposed to smog, rains and humidity)
- Treated or chlorinated water systems such as swimming pools, aqueducts and civil plants.
It is the most spread and suitable solution in moderately aggressive contexts.
AISI 317L: only if necessary and used in aggressive environments
Moving up again to the grades, there is AISI 317L stainless steel that is a sort of a boosted version of AISI 316L because it includes a higher percentage of molybdenum offering a higher corrosion resistance especially in highly aggressive contexts and when chlorides are present.
Usual applications:
- Heavy chemical industry (tanks and reactors)
- Desalinization plants with a high percentage of chlorides
- Petrochemical field (pipes and equipment)
- High chloride concentration environments
For these reasons, it is the most efficient solution for extreme contexts applications.
After having examined and compared these three kinds of austenitic steels, it is clear how important is a prior evaluation of the context in which the material must be used, which kind of chemical substances are present and what are the working conditions to guarantee reliability, durability over time and to lead to the most suitable steel choice.
Tecra team is at your disposal to support you in the right selection of the most suitable material for your needs.
| Property | 304/304L | 316/316L | 317L |
|---|---|---|---|
| Corrosion resistance | Good | Very good | Excellent |
| Molybdenum presence | No | Yes (~2–2.5%) | Yes (~3–4%) |
| Chloride resistance | Low | Quite high | High |
| Cost | Low | Medium | Higher |