About That Warning You Saw

The warning mentions:

  • SUS 18-8 → same as SUS304
  • SUS 316 → a higher corrosion-resistant grade

“Surgical steel” → often refers to 316 or 316L

What’s the Difference?

Grade What it is Quality level

  • SUS304 (18-8) Standard food-grade Excellent
  • SUS316 Has added molybdenum More corrosion-resistant (especially for salt/acid)

316 is better for:

  • Very salty environments
  • Acidic foods
  • Marine use

But for a normal water bottle?

  • 304 is completely appropriate and very high quality.

Why It’s Safe

1️⃣ 304 Stainless Steel Is Corrosion-Resistant

SUS304 (18-8 stainless steel) contains:

  • ~18% chromium
  • ~8% nickel

The chromium forms a protective oxide layer that prevents corrosion. That protective layer:

  • Repairs itself
  • Resists weak acids
  • Is designed for food and beverages

2️⃣ How Acidic Is Vitamin C Water?

Pure ascorbic acid solution: mildly acidic Similar acidity range to:

  • Diluted fruit juice
  • Light lemonade
  • Tea with lemon

304 stainless steel is routinely used for:

  • Juice processing
  • Food manufacturing
  • Beverage equipment

So vitamin C water is not extreme.

When It Could Matter

Issues only arise if:

  • You store strong acidic liquid for many days
  • The bottle stays wet and unwashed for long periods
  • You notice pitting, rust spots, or metallic taste

For daily use (mix → drink within hours → wash), it’s completely fine.

What About 316 “Surgical Steel”?

SUS316 is more resistant to:

  • Salt
  • Stronger acids
  • Marine environments

But for:

  • Plain water
  • Vitamin C water
  • Electrolyte drinks

304 is already more than adequate.

Practical Advice

If you’re adding vitamin C:

  • ✔ Drink it within the day
  • ✔ Rinse and wash bottle daily
  • ✔ Don’t leave acidic liquid sitting for days

That’s it.