Stainless, zinc-plated or galvanised: fasteners for outdoor and coastal sites
Use zinc-plated fasteners indoors, hot-dip galvanised for general outdoor steelwork, stainless A2 where it is damp or the fixing is on show, and stainless A4 within reach of sea air or chlorine. Matching the bolt, nut and washer finish matters as much as the finish itself.
Zinc-plated: dry, covered places
Electroplating leaves a thin zinc layer, often with a clear or yellow finish (labelled ZP or YZP). It looks clean and resists rust in dry, covered places: inside buildings, panels, furniture and machine guards. Outdoors that thin layer is soon used up.
Hot-dip galvanised: outdoor steelwork
Dipping steel in molten zinc leaves a far thicker coat that protects outdoor steelwork for years: structures, fencing, support channel and cable trays. Galvanised nuts are tapped slightly oversize to fit over the coating, so always use galvanised nuts with galvanised bolts.
See our hot-dip galvanised support channel.
Stainless A2 and A4: damp, visible and coastal
Stainless does not rely on a coating. A2 (grade 304) suits general outdoor work, kitchens, water and anything on show. A4 (grade 316) adds molybdenum to resist chlorides: coastal sites from Mombasa to Lamu, swimming pools and boats.
Standard stainless grades are not as strong as 8.8 steel, so check the load, and tighten steadily with a little anti-seize so the threads do not gall.
Mistakes that cause early rust
- Mixing metals in the wet: a stainless bolt in galvanised steel, or a zinc nut on a stainless bolt, makes the zinc corrode faster.
- Galvanised bolts with plain nuts, which leave bare threads.
- Cut or drilled galvanised steel left bare: touch the edges up with zinc-rich paint.
- Zinc-plated fixings on a roof or near the sea because they were the ones in stock.
Which one for the job
| Where | Use |
|---|---|
| Indoors, dry | Zinc-plated |
| Outdoor steelwork inland | Hot-dip galvanised |
| Damp, visible, kitchens, water | Stainless A2 |
| Coast, pools, chemicals | Stainless A4 |
Browse stainless screws and eye bolts, and ask us for A4 where you need it.
Not sure which fits your job? Send a photo and the load to us on WhatsApp +254 723 525243, or request a quote with your list.
Stainless and galvanised from our range
This wedge anchor is constructed from stainless steel, specifically the A2 property class. The fastener measures 12 x 100 and complies with the DIN 529 standard.
per Pcs
Questions buyers ask
Is galvanised the same as zinc-plated?
No. Both are zinc, but hot-dip galvanising is much thicker and lasts far longer outdoors; zinc plating is for dry, indoor use.
Which stainless is best near the sea?
A4 (316). A2 (304) can stain and pit in salty air, while the molybdenum in A4 resists chlorides.
Can I use stainless bolts with galvanised steel?
Indoors and dry, usually yes. Outdoors in the wet, isolate them with nylon washers or use galvanised bolts, because zinc next to stainless corrodes faster.