Keeping Rust Off an M9 Bayonet

Modern bayonets like M9 bayonets have been, by and large, made with relatively rust-resistant steel alloys in the 420 class. Those made by Ontario and Buck Knife Company, for instance, were made with relatively stainless steels that could withstand some moderate chemical attack without totally giving way to rust. 

But, as anyone that has ever handled a knife (especially) for any appreciable amount of time knows, there is no such thing as a truly stainless steel. If you get the conditions right (or wrong, depending on your perspective) any steel will eventually rust. 

So, with that said, how can you keep rust off an M9 bayonet? Let’s take a closer look at some high level notes that will keep your bayonets shinier for longer, and in better shape, all while preserving your investment in military collectibles. 

Preventing Rust 

The best way to keep rust off an M9 bayonet is to prevent it, rather than having to remove it after the fact. Fortunately that is relatively easy to do. 

If you use your M9 bayonet, that is, if you don’t just keep it in a display case and actually use it as a utility knife or for some other purpose, make sure you always clean it and dry it before putting it away. In fact, get in the habit of wiping off the blade and making sure it is dry before you even sheath it, even if you are in the field, temporarily. 

The same goes for whenever you come in from the field. Leaving an M9 bayonet in its sheath if there’s anything on the blade, especially moisture, is asking for a bloom of rust to materialize. 

So make sure you clean the blade off thoroughly whenever you get in and make sure it’s dry before you store it. You can keep it in the sheath for a prolonged period of time as long as it’s both clean and dry before you do so. 

One thing to note here is that you should pay special attention around the crossguard, where the shoulder of the bayonet meets the handle. This area can accumulate fouling, dust and other debris that can trap moisture and which will cause rust if it is not routinely cleaned away. 

Also, as a best practice, you should also get in the habit of oiling your blade before you store it. You can use any machine, gun or knife oil for this, but if you’re looking for something food safe a good option is to use tsubaki oil, also known as tea oil. This is commonly used to keep rust off blades.

Just make sure that the blade is completely dry before you oil it, as if you apply oil to a wet blade it will seal moisture against the blade and cause rust rather than preventing it. 

Also, if you are looking for something longer lasting, you can try microcrystalline wax, which does not evaporate like oil does. This is what museums and collectors use sometimes to keep moisture off steel, protecting it against corrosion and rust. 

After considering proper care of the bayonet, you also need to be smart about how you store it. It should be stored somewhere away from direct sunlight, but more importantly, where the humidity will be consistently low. 

The lower the better, but anything under 50% relative humidity, most of the time, should be fine. The lower humidity conditions will help minimize stress on the steel, preventing rust from materializing. 

But, we also recognize that sometimes, despite your best efforts, a blade will rust. That being said, here are some things you can do to remove it. 

Removing Rust 

This post will only consider the removal of light rust blooms from an M9 bayonet. Heavier rust and pitting will require more involved methods. 

Also, keep in mind that once you have rust on a blade, the finish will be damaged not just by the rust but by whatever method you choose to remove it. Still, that’s better than leaving rust on the blade.

Our best suggestion is to use a brass brush or fine steel wool to buff the rust blooms off the blade. Then, once you do that, wipe the blade down with a microfiber cloth to remove the rust residue, then apply a light coat of oil to the blade to help prevent rust from reappearing. 

And, as indicated, store the bayonet somewhere it will be protected against high humidity, which will cause rust in the first place.

Here for an M9 Bayonet? 

Need a new M9 bayonet for your collection? Take a closer look at our catalog of bayonets for sale which contains M9 models as well as other historically significant examples, and get in touch with us if you have any questions about anything in our collection before you buy.