What Is 18/8 Stainless Steel in Water Bottles? Grade 304 Explained

Jun 14, 2026

By Shiv Kohli

Quick answer: 18/8 stainless steel means the alloy contains 18% chromium and 8% nickel . This is Grade 304 — the most widely used food-grade steel globally. The chromium creates a passive oxide layer that makes the steel non-reactive: it doesn't rust, corrode, or leach metals into water under normal conditions. All HYV bottles use food-grade 18/8 stainless steel on all water-contact surfaces.

EXPLAINER·4 min read·Updated May 2026

What is 18/8 stainless steel in water bottles — grade 304 food safety explained India

⚡ Quick Answer

18/8 stainless steel means the alloy contains 18% chromium and 8% nickel. This is Grade 304 — the most widely used food-grade steel globally. The chromium creates a passive oxide layer that makes the steel non-reactive: it doesn't rust, corrode, or leach metals into water under normal conditions. All HYV bottles use food-grade 18/8 stainless steel on all water-contact surfaces.

18/8 Stainless Steel — The Numbers

18%

Chromium — creates non-reactive layer

Nickel — adds corrosion resistance

304

Grade designation (also written 18/8)

Leaching at normal temperature and pH

Why the Composition Matters

The 18% chromium content is what makes Grade 304 non-reactive. Chromium forms a thin invisible oxide layer on the steel surface that prevents direct contact between the iron in the steel and the liquid contents. Without sufficient chromium, steel corrodes and can leach iron into your water. Below 10.5% chromium, steel is not classified as stainless.

18/8 vs 18/10 vs 201 Stainless Steel

Grade	Chromium	Nickel	Food Safe?	Notes
18/8 (Grade 304)	18%	8%	Yes	Standard food-grade; used across HYV range
18/10 (Grade 316)	18%	10–12%	Yes	Marginally better corrosion resistance; medical/marine use
201 Stainless	16–18%	3.5–5.5%	Marginal	Lower nickel, lower corrosion resistance; used in cheap bottles
430 Stainless	16–18%	0%	Limited	Magnetic; no nickel; can rust in humid conditions

How to Identify 201 vs 304 in Practice

Magnet test: Grade 304 is non-magnetic or very weakly magnetic. A strong magnet attraction suggests 201 or 430 grade — which have lower chromium and nickel and less corrosion resistance. This is a screening test, not definitive — BIS IS 17526:2021 certification is the definitive verification.

Price test: 201 stainless steel is significantly cheaper than 304. A BIS-certified bottle using genuine Grade 304 at ₹400 is economically impossible — it's almost certainly a cost-cutting material grade.

HYV FlipFlow — 18/8 Grade 304

HYV LuxeSip — uncoated interior

HYV HydroMax — food-grade 304

💡 Interior Coating Risk

Some bottles use paint or epoxy coatings on the interior. Food-grade stainless steel doesn't need interior coating — bare Grade 304 is the correct and safest choice. HYV uses uncoated 18/8 steel on all interior water-contact surfaces.

Made by HYV

HYV makes insulated stainless steel drinkware in India. Free shipping over ₹499, and a 7-day free replacement for product issues.

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We go into this properly in Does a Magnet Tell You Whether a Bottle Is Real 304 Steel?.

Frequently Asked Questions

What is the difference between 18/8 and 18/10 stainless steel for water bottles?

Both are food-safe. 18/10 has marginally better corrosion resistance due to higher nickel content, but the difference is negligible for daily drinkware use. 18/8 (Grade 304) is the standard food-grade choice across all HYV products.

Is 201 stainless steel safe for water bottles?

201 stainless steel has lower chromium and nickel content than Grade 304, giving it lower corrosion resistance. It's generally considered acceptable for short-term food contact but is inferior to 304 for daily-use drinkware, particularly with acidic drinks.

Can you taste stainless steel in water?

No — food-grade 18/8 (Grade 304) with an uncoated interior is non-reactive and does not impart any flavour. A metallic taste indicates either a lower-grade steel, a degrading interior coating, or residue in the lid.

Are all HYV bottles 18/8 stainless steel?

Yes. All HYV bottles use food-grade 18/8 stainless steel (Grade 304) on all water-contact surfaces, with no interior coating or plastic liner.

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