Why do stainless steel screws also rust?

Update:06 Jul 2020
Summary:

The characteristics of stainless steel screws are bette […]

The characteristics of stainless steel screws are better, with strong corrosion resistance, high temperature resistance, and strong rust resistance. But it will still rust in harsh environments. For example, under very humid conditions, the stainless steel screws are exposed to the sun and wind every day. Over time, how much will definitely be rusty. For example, contact with some acid-base chemicals to cause chemical reactions. Cause corrosion and rust. There is also a bad stainless steel screw, for example, a product made of stainless steel SUS201 screw used in seawater. Due to the immersion for a long time, the original SUS201 stainless steel screw itself is not suitable for use on the salty seawater. Cause corrosion and rust. For the use of marine products, it is generally recommended to use stainless steel SUS316 screws, because 316 stainless steel screws carry corrosion and other properties are better.

 


When brown rust spots (spots) appeared on the surface of the stainless steel pipe, people were surprised: "Stainless steel does not rust, rust is not stainless steel, it may be a problem with steel." In fact, this is a one-sided misconception about the lack of understanding of stainless steel. Stainless steel will also rust under certain conditions. Stainless steel screws have the ability to resist atmospheric oxidation-that is, stainless, but also have the ability to corrode in the medium containing acid, alkali, salt-that is, corrosion resistance. However, the size of its anti-corrosion ability changes with the chemical composition of the steel itself, the mutual state, the use conditions and the type of environmental medium. Such as 304 steel pipe, in the dry and clean atmosphere, it has absolutely excellent corrosion resistance, but it is moved to the seaside area, and it will soon rust in the sea fog that contains a lot of salt; and 316 steel pipe shows good. Therefore, it is not any kind of stainless steel, which is resistant to corrosion and rust in any environment.