How to Restore a Rusty Knife Back to New

Some items are worth restoration; they could hold sentimental value by representing special occasions or gifts from someone special. It could even be a collector’s item because the production of the particular model ceased.

Sometimes we look beyond how the knife got rusty in the first place and decide to fix it first and focus on ensuring it does not get that bad again.

In this article, you will learn how to restore a rusty knife back to new with your bare hands a few simple tools you probably already have laying around at home.

Step 1: Disassembling the Knife

For restoration to be effective, you need to disassemble the knife so that you can have access to all the surfaces. This way, you can better visualize the damage and see what needs to be done.

Some joints, rivets and screws may be too rusty to operate, but this should not be a permanent setback. A lubricant such as WD-40 should do the trick of loosening them up.

Step 2: Cleaning the Knife

Clean each piece and section of the knife as thoroughly as possible because any dirt or debris might interfere with the rust removal process. This also helps eliminate any loose rust. Wipe the knife down thoroughly before proceeding to the next step.

Step 3: Removing the Rust

One of the most common methods of removing rust from a knife is using white vinegar. It is something many of us already have in our pantry at home. If not, it is an affordable option that works well for cleaning knives. White vinegar can work wonders on stainless steel and ceramic knives. 

Place each section of your disassembled knife in a container and pour enough vinegar over it to submerge the knife. Bubbles should start rising. This is an indicator of a reaction going on and will typically happen after a couple of minutes of being submerged in the white vinegar.

This means the rust is coming off. Don’t let the knife soak in the vinegar for more than 5 minutes, or the metal itself will start corroding and can result in irreversible damage.

White vinegar is preferred as it contains acetic acid, which attacks the rust instantly. Any other types of vinegar might stain the knife in the process.

If rust spots are still clearly visible, you can go to the next level of abrasion, which involves scrubbing and using a baking soda paste. The paste is created by mixing baking soda and water or lemon juice in a bowl and stirring it until it becomes a paste.

This paste is then applied to the knife parts and scrubbed using a toothbrush or any other available brush until the rust spots come off. If the rust stain proves to be stubborn, you can use steel wool or a semi-abrasive sponge to get leverage for applying more pressure.

A sharpening stone will be the ideal tool for this job, though. It is not a bad investment, given you will still utilize it later to sharpen your newly restored knife. A simple coarse grit whetstone like the KEENBEST Kitchen Knife Sharpener with a 400 grit surface will suffice.

When using white vinegar to restore a rusty knife back to new, make sure to rinse the knife and wipe it dry. While the vinegar helps remove rust spots and residual grease and residue on the knife, it can also damage a stainless steel finish when left too long.

Step 4: Sanding

The knife will still not be presentable enough to use after the rust has been removed; there may still be a rust stain or stubborn patches which need to be taken care of.

Apply coarse sandpaper first with a low grit of between 500 to 1000 to tackle the hard rust leftovers and scratches. After this, move on to finer grains of up to 2000 grit to even out the remaining scratches caused by the rough sandpaper.

Any stains that were on the surface of a stainless steel knife should be taken care of at this stage.

This step can also be executed on the whetstone, especially if only the knife blade is sanded. The other parts will have odd shapes that are better-taken care of with sandpaper.

Step 5: Polishing

This step is aimed at restoring a semblance of the glow the old rusty knife used to have. The SHARPAL 208H Buffing Compound works great for a medium to fine polish, and you can apply it using a leather strop on your knife to attain that desired mirror finish.

Step 6: Taking Care of the Deeper Rust Holes

You can remove these holes by sanding with the coarsest sandpaper available, a 60 grit, so the knife becomes smooth.

This, however, may result in a thinned blade, depending on how deep they go, and a thin blade is weak. The alternative will be to let them be and keep the rugged stonewashed appearance, but you need to take care of the rust in them.

One way is to spray WD-40 directly into the holes using their Smart Straw Spray canisters, enabling you to aim at the specific targets. The underlying concept is to avoid getting the spray on the blade’s cutting edge because WD-40 is strong and might corrode this delicate part of the blade and mess up its alignment.

It can also be harmful if ingested, and you don’t want it getting into contact with food, especially acidic food. We advise you don’t use the knife on food immediately after this exercise and that you wash it thoroughly.

Alternatively, restrict the use of WD-40 to larger knives like machetes that you won’t regularly use for cooking.   

If you decide to keep the rust holes, you can still use all the rust removal methods repeatedly to clean and polish your knife until you are impressed with the outcome. You can use steel wool while cleaning and a toothbrush to apply the polish because a leather strop might not get into all the groves.

Step 7: Sharpening the Knife

Depending on how bad off the knife was, you may require all three-grain ratings to restore the knife. If the blade is chipped, start with the coarsest whetstone grain, below 1000 grit, to level out the blade.

You can then smoothen it out with a finer grain between 2000 and 3000 grit. It is up to you to decide if you will go higher than this, depending on how you intend to use the knife.

After successfully restoring a rusty knife, the feeling is very fulfilling, especially if you did not need to break the bank to achieve the feat. It is definitely something we would recommend to consider for your prized knives.