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Can Stainless Steel Rust?

by Nov 15, 2017News

Many people are surprised to learn that stainless steel is not impervious to rust. However, this is not universally true. In fact, different types of stainless can have different levels of rust-resistance. Choosing the right type of steel for your application is imperative to ensure that you get the corrosion resistance that you need.

What Makes Steel Rust?

Understanding the science behind why some metals rust can help you understand why some other options, such as s31803 stainless steel, are more resistant than some other types.

Rust is a compound called iron oxide. It most frequently forms when iron and oxygen react to one another in the presence of moisture. Often the moisture present in the air is enough.

In some other cases, iron and the chloride in a salt water environment can react to create rust. This can be visible in rebar used in a seawall where it is repeatedly exposed to salt water, which can break it down over time.

In still others, high heat can cause the chromium and carbon to bond to one another and form carbides. This can happen at temperatures between 750 and 1550 degrees Fahrenheit. Steel that is damaged due to heat is considered “sensitized;” in some cases, it can be saved through complex heat treating, but in other cases, it is permanently damaged.

How do You Keep Iron from Rusting?

Iron is made into an amalgam with other metals to make steel. Stainless steel contains a combination of iron, carbon and chromium to prevent corrosion. It may also contain other elements such as manganese and nickel because of the qualities each of those introduce. However, the element most responsible for rust-resistance is chromium. The higher the chromium content, the less likely stainless steel is to rust. In general, stainless steel is made with anywhere from 10.5 to 30 percent chromium.

Choosing the Most Rust-Resistant Stainless Steel

There are roughly 150 types of stainless steel; these will have different compositions to accentuate different properties. Duplex stainless steel is typically a good choice. The chromium content of s31803 stainless steel is between 21 and 23 percent to ensure good corrosion resistance in a wide range of applications.

Type 304 is a popular and affordable stainless steel choice; however, it has a lower chromium content than otherwise similar 316. If your application involves exposure to moisture or saltwater, choosing the more expensive 316 can be a better and more durable investment.

We are always happy to help our customers decide which grade of stainless steel is the right one for their application. Get in touch today to discuss the best option for you.