Removing Patina from Carbon Steel – Should You & How to Do It
Carbon steels make up the majority of bushcraft knives and older collectible knives. Tool steel like O-1 date back to the first world war and there are hundreds of thousands of knives that are coated in a scaly buildup of stains and corroded metal that if removed would yield a vintage perfectly fine knife.
If you’re interested in restoring a knife and removing the patina from carbon steel, you have a few options.
But first, ask yourself…
Should you remove Patina?
Patina is usually the discoloration on a blade that isn’t heavy corrosion or scale buildup. In other words, stains that aren’t rust. Staining of the blade can happen the same way rust does but is harder to remove.
Patina is actually good for a blade in some cases because the patina forms a layer of oxidized steel that won’t oxidize any further. Depending on the purpose of the blade it may not be worth it to refinish it. (i.e. old bait knife tossed in the tackle box vs. your EDC blade)
Finally, what everybody will scream at you about is the value of the blade could be lost. Yes, in some rare cases you may destroy the value of a knife by refinishing it. Historical pieces like sabers, field knives or weapons used in a war or a knife carried by a celebrity or at an important event shouldn’t be restored. However, it’s your knife do as you please.
Things to Keep in Mind
- Having the right tools makes all the difference.
- Don’t break anything.
- You may need professional help.
The Best Methods for Removing Patina from Carbon Steel
Polishing the metal is actually removing very small amounts of metal in order to smooth out the surface and grain of the blade. Be careful when you go down this road. If you polish too much and go past removing the patina will leave you somewhere in between a rough sanding a mirror finish.
Most any metal polishing compound is going to work but polishing compounds for carbon steel are going to serve you best. Mothers creams are one of the best and my favorite.
If you decide to start out removing the patina with abrasives, use the least invasive products first. Scotch-Brite works wonders, the big guns after that is automotive grade sandpaper. Start with the highest grit sandpaper that will remove the patina. Always use water or oil to lubricate this process.
Remove all the patina and then work back up to the highest grit sandpaper you can find, should be around 2000-3000grit, and then buff it with Scotch-Brite. You’re almost refinishing the blade during this process, work slow do your research and do it right. You’ll be glad you did.
If you have the equipment, media blasting or rock tumbling the blade will remove all the patina in short order. If you’ve never done this sort of work before, don’t start out by blasting away your favorite knife.
Work up on scrap pieces to get the finish you like and then prep your knife by removing everything you can, and taping off anything that can’t be removed and you don’t want to be blasted.
How NOT to Remove Patina…
Wire brush - Other steel components are sometimes okay for cleaning your knife. 000# steel wool, for example, can help you clean up your blade extremely quickly. On the other hand, taking a wire wheel or a wire brush and going to town will most likely gouge your blade. Be patient and do the job right.
Cheap Sandpaper - Sandpaper is used by the world’s finest knife makers to put a finishing touch on a blade. They also use the world’s finest sand paper. Companies like 3M and Norton, my favorite, make very top shelf sandpaper for use on steel. Get yourself some!
Harsh Chemicals - Don’t dip your blade in Naval jelly which is phosphoric acid. Blades can be damaged by the harsh chemicals and often, by removing the rust with chemicals you’re going to stain the blade and be back to square one anyway!
If you decide that you want to clean up your old rust shank into a good bushcraft or EDC blade, proceed. Ignore everyone else who may talk you out of it. Gets your hands on the right tools, set aside a long afternoon, and get at it, you’ll be glad you did!
Knives were meant to be used and removing the years from a blade is just a new slate for you to work the blade until it’s time for you to clean it again.
* Photos from Flickr