The old Melbourne counter sold three alloys loudest: 304 for benches and food plant, 316 as the marine ticket, and 430 for magnetic indoor work. That split still matches how Australian merchants bin sheet. It is also where most expensive mistakes start — a coastal balcony specified in 304, a cooktop splashback in raw 430, a “marine grade” stamp treated as seawater armour.
Start with the chemistry, not the brochure. 304 is an 18/8 austenitic (about 18% chromium, 8% nickel). 316 keeps the chromium and nickel and adds molybdenum, which is why it lasts longer around chlorides. 430 is ferritic: little or no nickel, magnetic, cheaper, and the wrong answer outdoors in most Australian postcodes. Duplex grades such as 2205 sit above 316 when a tank, shaft or seawater duty needs strength and chloride resistance together.
The 304 versus 316 stainless steel in Australia essay is the decision tree most fabricators need. If a client has already said “marine grade,” read what marine-grade stainless steel actually means. Kitchen and processing work should go through food-grade stainless steel in Australia before anyone orders a No. 4 sheet. Magnetic mystery metal is covered in what 430 stainless steel is for and how to identify a stainless steel grade.
ASSDA — the Australian Stainless Steel Development Association — is the public body we treat as first among equals when a mill data sheet and a sales email disagree. A heat number on a certificate beats a verbal “it’s 316, mate.”
The rest of the mill book sits next door. Sheet, plate and finishes is how the alloy becomes a face you can clean. Custom-cut stainless and sections is how it becomes a blank, a bar or a hollow. Marine, balustrade and outdoors is where 316 stops being a slogan. If the metal is already on site and nobody stamped it, start with how to identify a stainless steel grade before you weld the mystery offcut into a coastal rail.