GUIDES
Eight guides, one question at a time.
Each guide answers a recurring technical decision — which grade, which process, which certificate level — with a deciding criterion, not a list of generalities. The short answer runs a few sentences; the rest develops it, puts numbers on it, and names where it stops applying.
304 or 316 stainless steel: which should you choose?
The difference between 304 and 316 is molybdenum: 2 to 2.5% in 316, none in 304.
316L or duplex 2205: when is it worth changing family?
2205 earns its place in three cases: where chlorides exceed what 316L can hold, where chloride stress corrosion cracking is the main risk, or where its yield strength — roughly double that of a 316L — allows a thinner wall and therefore a cheaper finished item.
Duplex or super duplex: where is the boundary?
The boundary is seawater.
Welded or seamless tube: which should you choose?
Where the standard is met, a welded tube and a seamless tube of the same grade and size have the same mechanical properties and the same corrosion resistance.
Stainless steel families: austenitic, ferritic, duplex, martensitic
Four families, defined by crystal structure.
Which grade for seawater?
Neither 304L nor 316L holds seawater: their PREN of 19 and 25 sits far below the threshold of around 40 required for that service.
Specifying stainless tube without getting it wrong: the eight points to state
Eight pieces of information are enough: the grade (by its EN number or UNS, never the AISI alone), the size (outside diameter and wall thickness, or DN/SCH, never one for the other), the product standard, the process (welded or seamless), the delivery condition, the length, the quantity, and the certificate level.
EN 10204 material certificates: 2.1, 2.2, 3.1 or 3.2?
EN 10204 defines four types.