Stainless 304 vs 316: Which Lasts on the NZ Coast

Walk through any new subdivision in Whangaparāoa, Mount Maunganui, or Christchurch's eastern suburbs and you'll see the same thing: entrance handles that looked brand new at handover, rust-stained and pitted three years later. Almost every time, the cause is the same. The handles were 304 stainless, not 316.

The chemistry difference, in plain English

Both 304 and 316 are austenitic stainless steels. The difference is one element: molybdenum. 316 contains 2–3% molybdenum, 304 contains none. Molybdenum is what makes 316 resistant to chloride attack — and chloride is what coastal air carries in salt spray.

304 will hold up fine inland. Put it within 5 km of the sea, and within a year or two you'll start seeing tea-staining: brown discolouration that looks like rust but is actually surface oxidation triggered by chloride ions. Wipe it off and it comes back. Eventually it pits the surface.

How to tell what you've got

This is the frustrating bit. 304 and 316 look identical out of the box. The only ways to be certain:

• Manufacturer's spec sheet — and only if it explicitly says "316" or "1.4401".
• A magnet test won't help (both are weakly magnetic at best).
• An XRF gun, if you happen to own one.

Generic "stainless steel" without a grade callout is almost always 304. If a hardware listing doesn't name the grade, assume the cheaper option.

Why we only sell 316

Every pull handle in our stainless handle range is 316 marine-grade. We made that decision because we're a New Zealand manufacturer selling to a New Zealand market, and 70% of our population lives within 10 km of the coast. There's no reasonable use case in this country for 304 on an external entrance handle.

What about powdercoated finishes?

Our powdercoated handles (matt black, bronze, custom colours) are 316 stainless underneath the coating. If the coating ever chips or wears through, the base metal still won't rust. Powdercoat over 304 looks fine until the coating breaks, then you get rust bleeding out from underneath — a problem you'll see on a lot of imported black handles.

The simple test before you buy

Ask the seller to confirm in writing that the handle is 316 / 1.4401 grade. If they hedge, walk away.