What separates the two grades
304 and 316 are both austenitic stainless steels — the workhorse grades for fasteners. The difference is in the alloy: 316 carries an addition of molybdenum that 304 doesn't have, and that addition is what gives 316 its markedly better resistance to chlorides — the salt in sea spray and the chlorine around pools. Chlorides are what attack stainless steel at a local level, causing the pitting and staining you see on coastal hardware.
In plain terms: 304 is a high-corrosion-resistance material for general coastal and exterior work. 316 — often called marine grade — is the step up for environments where chlorides are constant and concentrated. The price difference between the grades is real, so the decision is worth making deliberately rather than defaulting either way.
Where each fits on the Sunshine Coast
- 304 is generally suited to: exterior work in the moderate coastal band — Buderim, Sippy Downs, most of Maroochydore — plus sheltered coastal applications, interior wet areas, and jobs where fixings get rain-washed and ventilated.
- 316 is the call for: direct marine exposure — beachfront and near-beach suburbs like Mooloolaba, Kings Beach, Caloundra, Noosa Heads, Coolum, Mudjimba, Marcoola and Twin Waters — plus anything around pools, canal and estuary frontage, and balustrade or wire systems that live in the salt.
- Pool fencing and barriers: 316 is the spec we work to, full stop. Chlorinated splash zones chew through lesser grades.
A note on appearance: coastal stainless — including 316 — can develop tea staining, a brown surface discolouration caused by salt deposits sitting on the metal. It's cosmetic rather than structural, 316 resists it better than 304, and a periodic fresh-water wash-down keeps exposed stainless looking right. Smooth, polished finishes hold up better than rough ones because salt has fewer places to sit.
How to choose
- Distance and exposure first. Within about a kilometre of the surf, or anywhere salt spray reaches directly, 316 is the safer call. Further back, 304 usually does the job.
- Chlorine changes everything. Any fixing near a pool — fencing, gates, glass clamps, handrails — goes 316 regardless of how far you are from the beach.
- Think about wash-down. Fixings under eaves or in sheltered corners never get rinsed by rain, so salt accumulates. Sheltered plus coastal pushes you toward 316.
- Check what it touches. Stainless in contact with galvanised steel or aluminium sets up a galvanic couple. That's a separate check from grade selection — see the galvanic corrosion guide.
- Visible and hard to replace? Step up. Balustrades, feature screws and anything set in glass or masonry cost far more to swap out than the grade difference cost up front.
Common mistakes
- 304 at the poolside. The most common stainless failure we see. Chlorinated splash on 304 pits and stains fast — pool hardware is 316 territory.
- Assuming stainless can't mark. Tea staining on beachfront stainless surprises people. It's manageable with grade selection and wash-down, but "stainless" doesn't mean maintenance-free at the beach.
- Paying for 316 where 304 does the job. Inland or well-sheltered work rarely needs marine grade. Spend the difference where the exposure actually justifies it.
- Driving stainless like hardened steel. Stainless screws are less forgiving to drive than hardened carbon steel — use the right driver, drop the torque, and pre-drill hardwoods. For self-drilling into steel or dense hardwood, that's where bi-metal screws come in.
- Mixing grades on one detail. A 316 balustrade with 304 fixings weathers unevenly — the fixings stain first and the whole job looks tired.
Getting it specced
We stock both grades across screws, bolts, nuts, washers and balustrade hardware, and we'll tell you honestly which one the job needs — including when the cheaper grade is the right answer. Spec documentation is available with your order on request. Final grade selection for a specific application rests with the builder, engineer or certifier.