Why did my stainless steel mesh rust?

Is rust on stainless steel mesh a sign of counterfeit or inferior product? Possibly, but probably not. To answer this question, we first need to understand: Why does stainless steel rust?

Stainless steel is "rust-proof" because it contains chromium (Cr) (typically at a concentration of 10.5% or more). Chromium reacts with oxygen in the air, forming an extremely thin, dense, and strong passive film (primarily composed of chromium trioxide, Cr₂O₃) on the stainless steel surface. This film isolates the iron inside from the water and oxygen outside, thus preventing rust.

Main causes of stainless steel mesh rust:

Rust occurs when this passive film is damaged and unable to repair itself.

▲1. Chloride Ion Attack (Most Common Cause)

Culprits: Salt (sodium chloride), seawater, sea breeze, sweat, disinfectants, etc.

Mechanism: Chloride ions (Cl⁻) have extremely strong penetrating power. They can locally destroy the passive film and react with the metal, forming a "small anode, large cathode" corrosion cell, leading to rapid pitting corrosion. You'll see small rust spots appearing on the surface.

Scenarios: Stainless steel mesh used at the beach, kitchen filters exposed to salt, and mesh baskets stained with sweat are all susceptible to rusting due to chloride ions.

▲2. Surface Damage or Contamination

l Mechanical Damage: During processing, cutting, welding, or installation, the surface of the stainless steel mesh may be scratched or bumped, damaging the integrity of the passive film and making the damaged areas the starting points for rust. Welded and damaged areas (weld slag, heat-affected zones) are particularly susceptible to rust.

l Contamination from Adherent Iron: This is a very common cause. During manufacturing, transportation, or installation, ordinary carbon steel (such as iron filings and iron powder) may be cut or polished nearby. These iron filings can fall and adhere to the surface of the stainless steel mesh. In a humid environment, these iron filings will rust first, and the rust can spread and damage the underlying passive film. l Dust and organic matter: Dust, oil, soup, and other contaminants adhering to the surface can block the passive film's contact with air, weakening the film's function in that area and thus inducing rust.

▲3. Material Issues

Improper Grade Selection: Stainless steel comes in many different grades, each with varying degrees of corrosion resistance. If you mistakenly choose a non-corrosive grade for use in a harsh environment, rust is inevitable.

201 or 202 materials: These have high manganese content and low nickel content, resulting in poor corrosion resistance and are particularly susceptible to rust in humid environments. Some inexpensive stainless steel mesh may be made of this material.

304 material: The most common food-grade stainless steel, with excellent corrosion resistance, is suitable for general environments and kitchens. However, it may still rust in high-chloride environments (such as at the seaside).

316 material: Contains molybdenum (Mo), which significantly improves resistance to chloride ions, making it more suitable for harsh environments such as at the seaside and in chemical plants. Counterfeit and Substandard Products: Products on the market may be made from inferior stainless steel, such as 304, which may not meet rust resistance standards. Alternatively, the raw materials produced by the steel mill may contain high levels of impurities. Even if the nickel and chromium content meets standards, rust may still occur due to variations in other components or excessive impurities.

▲4. Electrochemical Corrosion (Bimetallic Corrosion)

Principle: When stainless steel mesh comes into direct contact with a metal with a lower potential (such as carbon steel, aluminum, zinc, etc.) in the presence of an electrolyte (such as water or humid air), a galvanic cell is formed. The low-potential stainless steel acts as the anode, accelerating corrosion.

Scenario: Stainless steel mesh secured with ordinary iron nails; stainless steel mesh baskets placed next to ordinary steel racks and exposed to rain.

▲5. Intergranular Corrosion

This typically occurs after welding or improper heat treatment. Within a specific temperature range, carbon combines with chromium to form chromium carbide, which precipitates at grain boundaries. This reduces the chromium content near the grain boundaries, creating "chromium-depleted zones." These chromium-depleted zones are unable to form an effective passivation film, allowing corrosion to occur along the grain boundaries in corrosive media. This condition can cause the material to lose strength and lead to overall corrosion.

How to prevent stainless steel mesh from rusting?

1. Correct material selection: Choose the appropriate stainless steel grade based on the intended use environment. 304 is generally sufficient for kitchens, while 316 is recommended for coastal or industrial areas.

2. Keep it clean: Clean the stainless steel mesh regularly to remove salt, sweat, oil, dust, and any possible iron filings.

3. Avoid scratches: During installation and use, minimize mechanical damage to the surface.

4. Prevent contact: Avoid prolonged direct contact with dissimilar metals (especially carbon steel), or use insulating spacers at contact points.

5. Prompt treatment: If even minor rust is detected, clean it immediately with a stainless steel cleaner, a scouring pad, or a soft-bristled brush. Rinse thoroughly with water and allow the passive film to naturally reform in the air.

Rust on stainless steel mesh isn't caused by "fake" conditions, but rather by the destruction of the protective passive film on its surface and the excessive presence of corrosive agents (especially chloride ions) in the environment. Understanding this will help you better select and use stainless steel products, maximizing their corrosion resistance.

In woven mesh products, embossed weaves may develop rust. This is because the stainless steel wire undergoes a cold-working process, which easily damages the surface oxide film. To avoid this, use high-quality stainless steel raw materials and take protective measures during transportation and storage, maintaining a dry and clean storage environment. Dashang Wire Mesh strictly selects austenitic stainless steel raw materials from renowned steel mills such as Qingshan Taiyuan Iron and Steel Co., Ltd. We perform spectral analysis on each batch of raw materials to ensure that the content of core elements such as chromium, nickel, and molybdenum meets national standards. Each batch of raw materials is controllable and traceable.