Why can stainless steel screws prevent rust?

The reason why stainless steel screws can prevent rust is mainly due to their unique alloy composition and the characteristics of surface chemical reaction. One of the most important alloying elements is chromium, which usually accounts for more than 10.5% of the stainless steel alloy composition. Chromium has a strong affinity for oxygen. When it is exposed to air, it can react quickly with oxygen to form an extremely thin but very dense chromium oxide film. Although this oxide film is thin, it is very hard and not easy to peel off. It can effectively block further intrusion of moisture, oxygen in the air and other corrosive substances, protecting the screws from rust and corrosion.
The self-healing property of this chromium oxide film is another major advantage of its anti-rust ability. When the surface of stainless steel is damaged by mechanical damage or other external factors, the exposed metal part will quickly react with oxygen in the air to regenerate a new oxide film. This self-healing ability allows stainless steel to maintain strong corrosion resistance during long-term use, and it can be used for a long time without rusting even in harsh environmental conditions.
In addition to chromium, other elements such as nickel, molybdenum, titanium, etc. also contribute to the corrosion resistance of stainless steel. Nickel can increase the toughness and oxidation resistance of stainless steel, especially in low temperature environments. The addition of molybdenum (such as the content in 316 stainless steel) further improves the resistance of stainless steel to chlorides, acidic substances and salts, so it can be used in highly corrosive environments such as the ocean and chemical industry, and is not prone to rust.
The corrosion resistance of stainless steel is closely related to the composition of its alloy and the oxide film formed on its surface, which is why stainless steel has stronger rust resistance than ordinary steel. Ordinary steel lacks this dense oxide film and is easily exposed to air and reacts with oxygen to form rust, leading to corrosion. The oxide film of stainless steel plays a natural protective role, greatly extending its service life.
The good corrosion resistance of stainless steel in many applications makes it an ideal choice, especially in humid, salt spray or chemical media environments. Even under these harsh conditions, the oxide film on the surface can still effectively prevent rust and corrosion. Because of this, stainless steel screws are widely used in construction, medical, food processing, chemical, marine and other industries, which are usually faced with harsh environments and long-term use.
Although stainless steel has good corrosion resistance, it is not completely immune to all corrosive environments. For example, in some extremely acidic or alkaline environments, the chromium oxide film may be damaged, thereby reducing its anti-corrosion effect. In this case, it is necessary to choose a more corrosion-resistant alloy type or add additional protective coating on the surface.