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Understanding why stainless steel rusts can help you better protect your valuable items. Although stainless steel is known for its corrosion resistance, it can still develop rust under certain conditions. Here are some frequently asked questions to help you understand and prevent rust on stainless steel.

What is stainless steel made of?

Stainless steel is an alloy composed primarily of iron and at least 10.5% chromium. It also contains smaller amounts of other elements such as carbon, silicon, and manganese. The chromium in the alloy is what gives stainless steel its corrosion-resistant properties.

Why does stainless steel rust?

Despite its name, stainless steel can rust. This occurs when “free iron” is present on the surface of the stainless steel, which is not protected by the chromium oxide layer. The free iron can come from various sources and is prone to rust when exposed to air and moisture.

What is the role of chromium in stainless steel?

Chromium in stainless steel forms a thin layer of chromium oxide on the surface, known as the “passive layer.” This layer protects the steel from corrosion and can even repair itself if it gets damaged.

What is free iron and why does it rust?

Free iron refers to iron particles that are not bound within the stainless steel alloy. These particles can rust because they are not protected by the chromium oxide layer. Free iron can be introduced to the surface through various means, including contamination during manufacturing or exposure to other iron objects.

How can free iron be removed from stainless steel?

Free iron can be removed through a process called passivation. Passivation involves treating the stainless steel with an acid solution that removes free iron and allows the chromium to form a new, protective chromium oxide layer.

What is passivation and how does it help prevent rust?

Passivation is a chemical treatment process used to remove free iron from the surface of stainless steel. By removing these contaminants, passivation allows the chromium in the stainless steel to form a continuous, protective layer of chromium oxide, which helps prevent future rust and corrosion.

Can passivation be done at home?

While passivation can technically be done at home using specialized solutions, it is typically performed by professionals to ensure thorough and safe treatment. Professional passivation services can provide the best results in protecting your stainless steel items.

By understanding the causes of rust on stainless steel and the methods to prevent it, you can ensure your stainless steel items remain in pristine condition. Using processes like passivation, you can effectively remove free iron and maintain the protective properties of the chromium oxide layer.

Solvent Recycling Systems, LLC