Stainless steel
Honestly, up front: there is no anti-dumping duty on stainless. Regulation (EU) 2022/191 explicitly excludes stainless steel, and the older measure on stainless fasteners from China and Taiwan expired on 8 January 2017. The price advantage that duties create in carbon steel does not exist here. The reason to buy in Taiwan is quality, consistency and supply security, not the tariff.
What does cost money is choosing the wrong grade. A2 is not a coastal material. In chloride-rich environments A4 is the minimum, and in an indoor swimming pool even A4 is not enough: there, stress corrosion cracking is a real and documented safety risk.
Grades
- EN ISO 3506-1
- Corrosion-resistant stainless steel fasteners, mechanical properties.
- A2
- Austenitic, approximately 304 / 1.4301. Interior and moderate exterior use.
- A4
- Approximately 316 / 1.4401, with 2 to 3 per cent molybdenum. Substantially better against chlorides.
- A5
- Stabilised 316Ti / 1.4571, for elevated temperatures.
- Duplex 1.4462
- Higher strength and better resistance to stress corrosion cracking.
- HCR 1.4529 and 1.4565
- Super-austenitic, for indoor pools, tunnels and seawater splash zones.
- Passivation
- Passivated fasteners are marked with a P.
Strength classes
- A2-70
- 700 MPa tensile, yield around 450 MPa. The standard.
- A2-80
- 800 MPa, more heavily cold worked.
- A4-70
- 700 MPa in the molybdenum-bearing grade.
- A4-80
- 800 MPa. Effectively the ceiling in standard austenitic stainless, comparable to 8.8.
- A4-100
- 1000 MPa, limited availability and worth checking per size.
- Why not 10.9
- Austenitic stainless does not harden by quenching and tempering. If you need both corrosion resistance and high strength, look at duplex or at coated carbon steel.
Corrosion in practice
- Galling
- Cold welding of the threads under load. The passive oxide film breaks, does not reform fast enough, and the flanks seize together.
- Preventing galling
- Lubricant or anti-seize, drive slowly without an impact driver, coarse thread over fine, and rolled rather than cut threads.
- Stress corrosion cracking
- In indoor pools, 304 and 316 under tensile stress can crack at ordinary temperatures. Fatal collapses are documented at Uster in 1985, Steenwijk in 2001 and Tilburg in 2011. Use HCR.
- Galvanic corrosion
- Stainless against aluminium or galvanised steel in wet or salty conditions attacks the less noble metal. Isolate with a polymer washer or coating.
- Magnetism
- A2 and A4 become slightly magnetic through cold working. That is normal and says nothing about quality.
- Pitting and crevice corrosion
- Form in stagnant chloride-rich moisture, precisely where surfaces do not rinse.
Applications
- Solar mounting: by far the largest stainless application, generally A2 inland and A4 on the coast.
- Greenhouse construction: permanent condensation, A2 as a minimum and A4 where crop chemicals are involved.
- Marine and offshore: A4 as the floor, duplex where strength also matters.
- Food processing: A4 for cleanability and chloride-bearing cleaning agents.
- Facade and cladding: A4, and HCR within a few kilometres of the sea.
- Swimming pools: HCR only in the vapour zone. This is a safety matter, not a budget one.
Last checked:
No duty advantage, a real quality difference
There is no import duty to save on stainless, so judge Taiwan here on what it does deliver: consistent quality, reliable documentation and supply security outside China. If your current supplier already meets that, I will say so.