The Cutting Edge

The official blog of Knife Depot

Category: Knife Maintenance

How to Remove Rust From the Blade of Your Knife

Whether you’ve found a knife in one of your old toolboxes or accidentally left your favorite knife outside in the rain, chances are you have encountered a nasty case of rust.

Many old timers considered rust the sign of a knife’s quality, but a rusted knife is also dangerous, useless, and downright ugly.

We originally wrote this post way back in December 2011, but we thought it’d be a good idea to do update it with some better information, videos, and recommendations.

What is Rust?

If you only want to some methods for removing rust, skip these next two sections, but it will be helpful to learn more about why your blade is rusting.

First, let’s tackle the nature of rust.

Rust is the common name for a compound called iron oxide — that reddish-orange flaky stuff you see peppered on some metal. This forms when iron and oxygen react to moisture. It doesn’t even have to be water exactly, it could just be the presence of water in the air.

Here’s a more scientific explanation from How Stuff Works:

Iron (or steel) rusting is an example of corrosion — an electrochemical process involving an anode (a piece of metal that readily gives up electrons), an electrolyte (a liquid that helps electrons move) and a cathode (a piece of metal that readily accepts electrons). When a piece of metal corrodes, the electrolyte helps provide oxygen to the anode. As oxygen combines with the metal, electrons are liberated. When they flow through the electrolyte to the cathode, the metal of the anode disappears, swept away by the electrical flow or converted into metal cations in a form such as rust.

Why Do Knives Rust?

Here are the ingredients for rust: iron, water, and air.

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How to sharpen a knife with a whetstone

A picture of a whetstone sharpener and a knifeGot a dull knife, sharpen it with a whetstone

A dull knife is not only ineffective, but it can also be dangerous. If your knife is dull, you’ll have to use more pressure to cut, increasing the risk of slippage and injury.

There are numerous ways to sharpen a knife, including fancy, high-tech sharpeners, but one of the most reliable–and affordable–is the whetstone.

What is a whetstone

Whetstone is a term for a number of natural or artificial stones that have properties making them ideal for sharpening. Artificial whetstones are composed of components such as ceramic, silicon carbide or aluminium oxide. These stones are usually double-sided with coarse grit on one side and a fine grit on the opposite side.

Natural whetstones, which typically have finer grades and are best used with oil, are often made from the material Novaculite, which is a variety of quartz.

Preparing to sharpen a whetstone.

The first step in knife sharpening is to lubricate your whetstone. You’ll want to either use oil or water for this process, depending on what type of whetstone you have.

Start by placing your whetstone on a paper towel that sits on top of a cutting board. then soak your whetstone in the lubricant of your choice for approximately twenty minutes. If your whetstone has both a fine and coarse side, you’ll want to start sharpening on the coarse side.

Finding the correct angle for sharpening a whetstone

Most knife experts agree that the ideal angle for knife sharpening for a whetstone is 20 degrees. You’ll want to sharpen your knife using smooth motions. Make sure you perform equal strokes on each side. A good rule of thumb is to perform five strokes on each side of your knife and then touch it; you should be able to feel the difference. The motion should be slow and smooth–never jerky–and should resemble the way you would slice a thin piece of meat.

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Knowing vulnerabilities in blade material key to maintenance

Last week, in one of Martha Stewart’s Q&A articles at Cincinnati.com, a reader raised an important aspect in maintaining knives: what material the blade is made out of.

Whereas most modern kitchen knives are created out of stainless steel, the blades of many older models are other materials, such as carbon steel.The problem with carbon steel blades, as the reader had found out, is that they are vulnerable to discoloration.

Stewart’s solution for the brown blade was fairly simple:

You can brighten your knives’ blades by polishing them with fine steel wool and Noxon metal polish. In addition, collecting editor Fritz Karch recommends hand-washing the knives after each use and drying them immediately to prevent rust. Then, with a cloth or paper towel, wipe a thin layer of mineral oil onto the blade to protect the steel from corrosion. Finally, store them in a location with low humidity.

Although the question was aimed at kitchen cutlery, this topic is something all knife owners should consider. As Stewart pointed out, always cleaning carbon steel blades, whether kitchen cutlery or hunting knives, is crucial to keeping its color and durability.

Each blade material has specific tips to remember. For example, stainless steel blades have the potential to rust in certain environments, so drying and occasionally scrubbing them with abrasive cloth will preserve the blades’ integrity.

For ceramic blades, found in some folding knives and kitchen cutlery, they will not rust or suffer discoloration, but they are more susceptible to scratches and breaks.

Whether plastic, titanium, stainless steel or carbon steel, it’s important for knife owners to understand the vulnerabilities of each blade material.

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