Yes — stainless steel is rust-resistant, but that doesn’t mean it’s rust-proof. When stainless steel is exposed to water for a long time, it can rust. Bleach can also cause the Hydro Flask to rust, as well as salt water and high heat (like that from a stove, microwave, or dishwasher).
Keep your Hydro Flask clean and let it fully dry occasionally. If you notice rust, remove it with our vinegar or baking soda trick.
Remember that if you can’t remove the rust, you’re covered by a 100-year warranty.