Can Stainless Steel be Anodized? Answered

Stainless steel can't be anodized because the electrolyte baths used in the anodization process would corrode and dissolve the stainless steel surface, damaging the part. However, many alternative methods provide comparable results to anodizing, like passivation, heat coloring, hard coating, painting, black oxide coating, etc.

This article explains the intricacies of anodizing stainless steel and discusses alternate methods to apply a clear or color coat on stainless steel parts.

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Anodizing Stainless Steel: Is it Possible?

The general answer is no, but there are exceptions.

Some manufacturers with enough resources are able to anodize stainless steel in a controlled environment by using a hot caustic solution.

Most companies that handle stainless steel will refer to their coloring process as stainless coloring, and their methods are often confidential.

Such techniques require special equipment and are not feasible for most hobbyists and small businesses.

Steel is made up of approximately 2% iron and carbon. When the iron in the steel comes into contact with the oxygen ions used for anodizing, it creates ferric oxide, which can cause the steel surface to peel off.

​​Anodizing is an electrolytic process that creates thick oxide coatings, often on aluminum alloys.

The oxide layer, which is usually 5 - 30 µm thick, is employed as a decorative layer to increase the surface's resistance to wear and corrosion.

Despite its excellent resistance to rusting, stainless steel can corrode under certain circumstances.

Luckily, there are some alternative methods that you can use to apply color or protective coats on stainless steel surfaces.

Alternatives to Anodizing Stainless Steel

Passivation - Is it "the" solution?

Since stainless steel doesn't form a natural oxide layer, it can't be anodized like in aluminum and its alloys.

Instead, a process called passivation is used on stainless steel parts. It creates a thin chromium oxide layer over the stainless steel, providing corrosion resistance and a better aesthetic appearance.

Passivation can be performed on stainless steel in a DIY setup, but it requires some knowledge of the process, equipment and chemicals, and safety precautions.

The process typically involves immersing the stainless steel in a solution of nitric or citric acid, which removes any contaminants on the surface of the stainless steel part and creates a thin oxide layer.

The temperature, concentration, and duration of the immersion all play a role in the effectiveness of the passivation process.

Hard Coating

The most popular method for color-coating stainless steel is hard coating. It is primarily used use to polish weapons and other associated equipment.

Hard coating is durable and can withstand a lot of damage. It's inexpensive but straightforward to use.

It is one of the finest methods to add a stable coating to a stainless steel surface.

Many brands offer hard coating kits for stainless steel, and the one from Cerakote is quite popular.

Heat Coloring

Heat coloring is known by other names like flame anodizing, flame coloring, heat coloring, temper coloring, and heat anodizing.

When stainless steel is heated to a specific temperature, its surface texture will be altered and deflect light of particular wavelengths, showing different color hues.

After the process, the colors you obtain will vary based on the grade of the stainless steel and the temperature at which it's heated.

So you can play around with different temperatures and steel compositions to get different color gradients.

Although it is not an anodizing technique, it produces results almost identical to those of anodizing titanium. There is no use of electricity during the process.

You can buy and use heat coloring kits to perform the coloring process. The process is simple, and you can even use a torch to heat it until its shows the desired shade.

Black Oxide Coating

The black oxide coating adds a protective black decorative finish to steel and other metal surfaces.

The process involves immersing the metal in a solution of ferrous oxide, which reacts with the surface to form a layer of black iron oxide.

It can be applied to both stainless and regular steel, although the exact process and result may vary depending on the composition of the steel.

Painting

Painting stainless steel is the most economical option. While certain paints might be costly, most of them are affordable.

Also, with paints, you'll have more color options available. You can also use anodizing paints to replicate the sheen and texture of an anodized workpiece.

Unfortunately, such metal paints will easily degrade and require frequent recoats.

Laser Coloring

Using a MOPA fiber laser also, you can alter the color of a stainless steel part.

You'll get different color markings based on the power, speed, and resolution setting you use for engraving.

On these machines, you can control the laser's pulse width and frequency, which can be used to create different colors on the stainless steel surface.

The specific colors and quality of the engraving will depend on the type of stainless steel and the settings used on the laser.

Final Thoughts

Though stainless steel can be coated using various techniques, it's important to note that not all grades of stainless steel can be processed using these techniques.

It's crucial to understand the properties of the specific grade before attempting to apply a coat.

Overall, coating stainless steel can improve the material's performance and appearance for various applications.

Frequently Asked Questions (FAQ)

Can you use stainless steel with anodized aluminum?

No, you can't use stainless steel with anodized aluminum because corrosion can occur between anodized aluminum and stainless steel. In addition, the oxidation of aluminum makes it passive during the anodizing process hence susceptible to localized corrosion.

What can destroy stainless steel?

Stainless steel is destroyed when exposed to grease, moisture, salt, or heat for extended periods. Therefore, despite having inherent corrosion resistance, stainless steel can rust under specific circumstances, though less rapidly and severely than standard steel.

Is there anything that takes scratches out of stainless steel?

To remove scratches from stainless steel, some effective products are available on the market, like 3M rubbing compound, Rolite metal polish, Bar Keepers Friend, etc. In addition, some everyday household products like non-gel toothpaste or baking soda can also remove scratches from stainless steel.