Does stainless steel rust? As a business owner using steel in manufacturing, construction, or any other, it’s imperative to know the mechanical properties of steel in order to use the right steel type. For instance, if you are seeking business opportunities with steel utensils, the choice of steel will be critical. Stainless steel is a steel alloy used in a wide variety of industries, especially in the food processing industry. It contains chromium which makes it rust and corrosion resistant making it a desirable material in various industries. However, even high-grade stainless steel is susceptible to rust after long exposure to air. Stainless steel rust can be removed easily and even prevented if the right provisions are made.

Let us take a look at what is stainless steel rust, what causes steel rust, and how to remove rust from stainless steel materials.

What is rusting?

Rust is the result of oxidation. Iron is the core raw material in steel. Hence when steel (or iron) comes in contact with moisture (water and oxygen) from the atmosphere it undergoes a chemical reaction. This results in the formation of a red or orange coating on the surface, commonly known as rust.

It’s important to keep in mind that though the primary reason for stainless steel rust is exposure to atmospheric moisture, rusting can also happen when the metal is exposed to specific chemicals, saline water, humidity, grease and extreme heat over a prolonged period.

Does stainless steel rust?

The next obvious question therefore is – Can stainless steel rust?

The simple answer to this is – stainless steel is resistant to corrosion and rust, but not immune to it.

Let’s understand why.

The composition of stainless steel, primarily chromium gives it its unique anti-corrosive properties. The chromium content however wears off after long periods of use and this makes the steel alloy susceptible to rust.

Based on what other alloying elements are being added to it (e.g., nickel, silicon, manganese, molybdenum etc.) the degree to which it is anti-corrosive can be modified.

Must Read: Stainless Steel grades chart

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Let’s understand rust in steel with the example of stainless steel 316 grade.

Grade 316 stainless steel contain 16%-18% chromium (high) and 2%-2.5% molybdenum and offers advanced resistance to corrosion from saline and moisture. This property makes 316 stainless steel the preferred building material especially in coastal areas, outdoor railings and panels (e.g., steel railings), roofing panels etc.

Also read: Stainless steel roofing sheets – Know what makes SS apt for roofing sheets

What are the different types of stainless steel corrosion?

When it comes to stainless steel corrosion, there are some common types:

• General steel corrosion: Corrosion across the entire metal surface uniformly based on degree of exposure to moisture and other acidic elements such as hydrochloric and sulphuric acid
• Pitting: Corrosion caused by chloride iron (e.g., in salt), resulting in holes caused by reaction to atmospheric chlorides
• Galvanic corrosion: Occurs in the presence of an electrolyte and two dissimilar metals, leading to one metal corroding more than the other
• Intergranular corrosion: Caused when the chromium combines with high carbon content in steel, especially during high temperature heating, where the chromium content is reduced leading to the metal boundaries corroding

What makes stainless steel rust resistant?

As explained in the previous section, stainless steel is a form of alloy steel – that is, by adding other elements to it (e.g., phosphorus, molybdenum, sulphur, titanium, etc.) it’s properties can be modified and enhanced.

The percentage or quantity of chromium present in stainless steel determines its sustainability to rusting. Higher the quantity of chromium, lesser the steel will rust. In general. A minimum of 10.5% of chromium is required to make a passive layer to prevent steel corrosion.

In general, stainless steel contains a thin surface layer of oxide, measuring no more than 5 nanometres. This layering makes the steel electrochemically passive when in a rust prone environment. This is known as the passive layer and enhances its rust-resistance properties.

Example – 

Grade 304 stainless steel contains chromium (17.5%-19.5%), carbon, nickel, but does not contain molybdenum.

Higher chromium content makes 304 grade SS resistant to rusting from oxidising elements (e.g., acids) making it suitable for use in decorative items, buildings, etc. However, lack of molybdenum in stainless steel 304 grade, makes it more prone to corrosion and rust when compared to grade 316. It is for this reason that grade 304 is not used much in appliances or areas exposed to salt and chlorides as its protective passive layer can easily be broken down, making the steel vulnerable to rusting.

Also read: Stainless Steel 304 vs 316 – Understand their key differences and where to use which

How to remove rust from stainless steel?

If your stainless-steel appliance has rust gathering on some parts, then it is time to remove the rust from stainless steel. To learn how to clean rust from stainless steel you need to know the right solutions that can treat the rust.

Here are a few methods you can apply to remove rust on stainless steel appliances:

Home remedies for SS rust remover

There are easy ways to do it with things that are easily found at home, or you can get stainless steel cleaning solutions available in the market. It’s advisable however that before you try any of the methods to clean stainless steel rust, get advice from an expert or refer to user manuals provided with the appliances.

Also read: Steel vs Stainless Steel – Differences, properties and which to use where

Use baking soda

Baking soda is hard and abrasive and can easily wipe away rust on your appliances or kitchen tops and sinks. Follow these instructions to remove rust using baking soda:

• Add baking soda and some water into a bowl
• Mix the ingredients until it forms a thick paste
• Rub the paste on the rust spot and let it soak for two-three hours
• Wipe off the paste with a soft cloth or wet paper towel

Use vinegar

You can use vinegar to wipe out the rust from your machines. Follow these steps to remove the rust:

• Pour a generous amount of white distilled vinegar on the rust spot
• Let it soak for two-three hours
• Get a soft scrub or a brush and scrub the rust off the surface
• Wipe the surface clean with a soft cloth or wet paper towel

Use lime/lemon

Lime and lemons can be powerful cleaning agents. Most dishwashing liquids in the market today contain the essence of lime. It can be used to remove rust as well. Here are the steps to follow to remove rust with lime or a lemon:

• Mix equal amounts lime juice and salt in a bowl to create a paste
• Apply the mixture to the rusted part of the machine and let it rest for two hours
• Rinse off with a soft cloth or wet paper towel

Commercial solutions for SS rust removal

You can also get commercial cleaning solutions available in the market. These are easy to use, and a quick spray of the cleaning solution can remove the rust. Some of these solutions are multipurpose and can be used on other metals as well.

How to use WD-40 stainless steel rust remover spray?

WD-40 can be used as a cleaning agent to remove rust from stainless steel. It is most effective on benches, steel railings, sinks or any other items that are often exposed to oxidisation and atmospheric moisture. It comes with a peculiar smell but is temporary and goes away after some time.

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• Spray the desired area with WD-40
• Let it sit for 30 minutes based on the rust thickness and age
• Wipe off with a gentle cloth

Also read: Modern steel railing designs – Ideas for secure, safe and aesthetic outdoor railings

Note: WD-40 stands for Water Displacement, Formula 40

Tips to remove rust from stainless steel

Given below are some tips to follow while you are cleaning the steel surfaces off the rust:

• Use nonabrasive clothes to wipe the surface (avoid metals wipers as it could react with the cleaning agent)
• Let the cleaning solution (commercial or homemade) rest for a while before wiping it off (recommended 1-2 hours before you rinse or as instructed)
• Put gloves on if you are using commercial cleaning solutions
• Use soft bristled brushes and soft scrubs to scrub the rust off the surface

How to prevent stainless steel from rusting?

If you are thinking about how to stop stainless steel from rusting, then the answer is in scheduling its cleaning and polishing. Whether its for kitchenware, cookware, utensils, or outdoor seatings, panels and railing, it’s recommended to have it cleaned and polished regularly. You can also follow these practical tips to reduce steel corrosion in general for all your projects.

While it’s convenient to use homemade cleaning solutions for home appliances and utensils, it’s challenging when rust formation has to be prevented on outdoor structures.

Also, avoid using hard water as it can contribute to deposits on the surface and lead to quicker rusting. You can instead get your water treated or install filters to remove corrosive elements.