Grade 304 stainless steel
Grade 304 stainless is 18% chromium 8% nickel: general external residential fixings, handrails, sinks. Will rust in salt air; coastal pool surrounds need 316.
Ask Chalkline about this →Grade 304 stainless steel is the austenitic stainless workhorse: nominally 18% chromium and 8% nickel (“18/8”), with corrosion resistance suited to most general external residential applications. It is not the same as grade 316L: 304 will pit and rust in marine or chloride-rich environments where 316 holds up. Picking the wrong grade for the environment is a common warranty failure.
Where 304 is fine
- General external fixings in inland or suburban locations: hinges, screws, brackets, light-duty wall ties.
- Kitchen sinks and splashbacks indoors.
- Internal handrails and balustrades in offices, public buildings, residential.
- Light-duty external work more than a few kilometres from saltwater spray.
Where 304 fails
- Coastal locations (within 1 km of breaking surf): salt aerosol pits the surface within months and rust streaks appear within 1 to 2 years.
- Pool surrounds and pool fencing: chlorinated air attacks the chromium oxide passive layer.
- Indoor swimming-pool halls and spa rooms: the chlorine atmosphere is more aggressive than open-air coastal use.
- Submerged or splash-zone marine work.
The fix is grade 316L (molybdenum-bearing marine grade) for any of the above.
Identifying 304
- A2 on fasteners (DIN/ISO) = 304.
- 18/8 = the Cr/Ni ratio.
- AISI 304 grade may be marked directly.
For a builder
- Default to 316 on coastal jobs. 304 looks identical out of the bag, then fails.
- Pool surrounds: always 316. Includes indoor pool spaces; chlorine atmosphere is the trigger.
- Don’t accept a merchant substitution either way. 304-for-316 swap is a warranty failure waiting.
Category: Materials / metals.
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Last updated: 2026-05-29. Verified: 2026-05-29. Quarterly review for currency.