What's your corrosion zone?

Salt aerosol thrown up by breaking surf is the big corrosion driver on the Coast. It travels inland on prevailing onshore winds, so corrosivity drops as you move away from the beach. Calm salt water — the Passage, river mouths, canals — throws less aerosol, so its influence band is narrower but still real at the waterfront. Time-of-wetness matters too: sheltered detail that never gets rain-washed can corrode faster than exposed steel.

Standard galvanised is fine inland and cost-effective. Class 3 and Class 4 coated screws carry heavier, tested coating systems for coastal work — Class 4 is the severe-marine grade. 304 stainless resists coastal air well; 316 adds molybdenum for surf-zone and immersion-adjacent work and is the safe call at the beachfront. Stainless costs more per box, but on a deck you can't rebuild cheaply, the fastener is the wrong place to save.

Two different metals in contact with moisture make a battery, and the less noble one corrodes first. Stainless screws into galvanised brackets accelerates the bracket's corrosion at the contact point. Match the system — or use purpose-built bi-metal fasteners and isolation. This is our specialty; ask us before you mix.

Prevailing onshore wind, low flat terrain, elevation, canal or estuary frontage, and unwashed sheltered detail can push a site harder than the map band suggests; good shelter and washing can ease it. The band is the starting point, not a site assessment — bring the address in and we'll talk through the exposure.