Stainless steel is highly resistant to rust, but it is not completely immune under all conditions. The key to its rust resistance lies in its chromium content, which forms a protective layer of chromium oxide on the surface, preventing oxygen and moisture from reaching the underlying steel. However, if this protective layer is damaged or if the stainless steel is exposed to highly corrosive environments, rust can occur.

Factors that can cause stainless steel to rust include:

1. Exposure to Chlorides: Environments with high levels of chlorides, such as coastal areas or contact with saltwater, can lead to pitting corrosion, especially in grades like 304 stainless steel. For better resistance, marine-grade 316 stainless steel is recommended.

2. High Temperatures: Elevated temperatures can enhance the corrosive power of certain chemicals, leading to oxidation and rust.

3. Mechanical Damage: Scratches or dents can compromise the protective chromium oxide layer, exposing the underlying steel to oxygen and moisture, which can result in rust.

4. Chemical Exposure: Harsh chemicals, including acids, can degrade the protective layer, making the steel susceptible to rust.

5. Improper Maintenance: Regular cleaning and proper maintenance are crucial to preventing rust. Using abrasive materials or not thoroughly drying the surface after cleaning can lead to rust formation.

While stainless steel is durable and resistant to rust under normal conditions, it requires careful handling and appropriate grade selection to maintain its corrosion resistance in harsh environments.