Firearms are typically made of metal, or at least have a large percentage of their components constructed of steel, aluminum, and various alloys. As such, they can be negatively impacted by undesirably high humidity levels wherever they are stored, but most particularly within a closed-in space like a closet, locker, or gun safe if humidity levels are not properly monitored and managed.
Understanding the impact of humidity on firearms and valuables
Museum curators with mixed exhibits typically aim for relative humidity levels between 25% and not more than about 60%, and for museum patron comfort, usually maintain temperatures at between 60-70°F. For books and paper records, the Library of Congress recommends cool temperatures and a relatively dry environment (30-55% relative humidity), but not too dry. Generally, firearms experts agree that a stable, relatively cool, and dry environment is best for the proper storage and preservation of firearms. For example, the NRA recommends keeping the humidity in your vault room or gun safe between 30% and 50% and the temperature at 70 degrees F or below.
Why is this? Because fluctuations in temperature and/or high humidity levels can accelerate corrosion, rust, and the breakdown of woods and polymers used in firearms. Even if you don’t touch or inspect your firearms, they can still be damaged just from sitting in a humid environment or in a place with extreme temperature swings. We generally try to err on the side of around 30% humidity (but not much drier than that, for reasons we’ll see below) and a stable temperature that’s as cool as is practical within your selected gun safe storage area or vault room.
Rust formation
Rust is an iron oxide, typically reddish-brown in color, that is formed by the reaction of iron and oxygen in the catalytic presence of liquid water or moisture (humidity) in the air. The rusting of iron is an electrochemical process that begins with the transfer of electrons from iron to oxygen. Technically speaking, iron is the reducing agent (gives up some of its electrons), while oxygen is the oxidizing agent (gains some electrons). In the process, hydroxides are formed, accelerating corrosion. This process is greatly accelerated if there is salt or chlorine in the available water.
In the firearms world, bluing, pickling, color case hardening, and browning are all various methods by which raw steel is intentionally oxidized for decorative and/or protective reasons. Why do gunmakers intentionally oxidize steel surfaces if oxidation is supposed to be bad? Well, if the surface of a carbon steel barrel is rust-blued, for example, the black iron oxide magnetite (Fe3O4) is formed, and this exposed black oxide surface seals off the raw iron below and helps prevent further transfer of electrons from the iron to oxygen, mitigating the undesirable oxidation (rust) of the barrel. If the firearm is stored properly (see below), the formation of rust can be greatly slowed or prevented entirely.
Video: How To Store Your Guns (Avoiding Rust and Scratches)
However, if humidity is higher than recommended, or if firearms are handled frequently with bare hands and not properly treated afterward, the moisture in the air and acids from the skin can cause rust to begin to form. Once it starts there is very little you can do to stop it, short of converting it to black oxide again in the conservation process.
Corrosion
Even non-ferric metals (those not containing iron) aren’t immune from corrosion. Corrosion may be galvanic in nature, where two dissimilar metals undergo an electrochemical process during which one metal corrodes preferentially when it is in contact with another in the presence of an electrolyte (such as water). Or it may simply be corrosion due to oxidation from the air, which happens to all metals at varying rates. Uncoated metal alloys and aluminum (even stainless steel) generally all oxidize somewhat when exposed to the air. In some cases, this is desirable, as the oxidation itself forms a barrier against further corrosion, similar to the browning or bluing described above. One of the most common forms of protection for aluminum and similar alloys is anodization, which is an electrolytic oxidation process by which the surface of a metal is (again, intentionally) converted to an anodic oxide/hydroxide film with desirable protective, decorative, or functional properties.
Various spray-on and/or baked-on coatings, such as DuraCoat, Cerakote, enamel, or similar, are also used on steel and aluminum firearm components. These can be useful in preventing corrosion and wear, but they are not flawless and often wear or crack off under use, exposing the metal below.
If the humidity in your safe or vault room is too high, corrosion of these non- or low-ferric metals can accelerate and may cause expensive or irreparable damage to your valuable firearms and other items.
Wooden and polymer components
Wood has been used as the furniture or stocks of portable firearms since around the 14th century and is still widely used today, though typically in more premium guns. Polymer has become cheaper and more durable than most woods, but both materials need proper care to avoid damage from humidity (or the lack thereof).
Wood is a biological material, primarily cellulose, and many wood finishes (particularly on higher-end firearms) are wood or seed oils. These materials can become the breeding ground for molds, fungi, and other nasty stuff if left in humid environments. Even some polymers can sprout or facilitate mold in a humid basement closet or gun safe, particularly if left undisturbed and uninspected for long periods of time.
While metal surfaces may do better in extremely dry environments, wood stocks actually contain a certain amount of water and require the proper amount of humidity in the air to maintain their size, shape, and integrity. Wood gunstocks stored in too-hot or too-dry environments will lose their internal moisture and begin to shrink, crack, or chip.
Certain solvents and oils can react with wood finishes or polymer firearm components, and these reactions may be accelerated in the presence of high humidity or too-warm temperatures.
Tips for safe storage
There are a few key points to consider when developing a strategy that provides security for your firearms and also keeps humidity at bay. Let’s go over some of the main ones.
Choose the right place for your gun safe or firearms storage
Obviously, this will depend greatly on the layout of your home, your personal security plan, and even things like whether people have basements in your area (some places don’t due to high water tables). You want to select a location for your firearms storage that aligns with your personal preferences, how often you want to access your guns, and also is temperature stable and has relatively low humidity.
Places like a non-climate-controlled garage, where temperatures can exceed 100° F in the summer and may drop below freezing in the winter, are certainly not ideal places to store firearms (or ammunition/reloading components). Neither is a musty, humid basement where water condenses on the walls and floor. In cases like this, placing your secure firearms storage device (it’s best to invest in a proper gun safe) indoors, in a part of the house where the temperature is relatively cool and doesn’t fluctuate much, is a better way to go. Radical temperature changes are not just bad for anything you want to keep in good shape for a long time but can cause condensation, which can lead to rust, mold, and corrosion.
Monitor humidity levels
It goes without saying that you need to check the humidity in your home and inside your safe regularly. Otherwise, you won’t know if it’s too humid for the safe storage of your guns and valuables. The way you check humidity levels is with a device called a hygrometer. A hygrometer is a humidity monitor (some also tell you the temperature) that informs you of the current moisture level in the air. Hygrometers have become very affordable and are really a must if you want to keep your guns in an ideal environment to prevent humidity-related damage. Once you know the humidity inside your firearm storage area, you can make adjustments if necessary.
Invest in a safe dehumidifier
If a whole-home climate-control system is not in the cards and your dwelling’s interior air is still above about 40% humidity, then a good gun safe with a proper safe dehumidifier inside is likely the best place for you to store your guns and valuables to prevent humidity damage.
There are a couple primary types of safe dehumidifiers. Plug-in/electric safe dehumidifiers like the Dry Rod Dehumidifier and the PEET Air Circulating Dehumidifier work by heating an electric element and maintaining it at a constant, safe temperature. This creates a circulation of slightly warm, drier air inside your safe (compared to the outside air) and this circulation and temperature differential drives humid air out of the safe. This is the kind of in-safe dehumidifier we recommend for most people with safes, especially if you have easy access to an electrical outlet and/or your safe already comes wired for lights and other electrical accessories.
You may ask about the effect of creating a warmer environment, since, as we mentioned above, the preference overall is for cooler temps. As we noted earlier, electric safe dehumidifiers circulate slightly warmer air throughout your safe’s interior. However, this temperature differential is only around 3 degrees. As a result, the temperature of the metal parts of your firearms increases just enough to eliminate the tendency of cold metal to condense moisture out of humid air. It also helps maintain a more consistent temperature within the safe, even if there are fluctuations in the outside temperature.
Additionally, when you use a good in-safe dehumidifier, wood stocks, and grips are kept at a temperature that discourages moisture from building up in metal-to-wood contact areas, where they are the most vulnerable to rust and corrosion.
The downside of using an electric dehumidifier is that it (obviously) relies on a steady supply of electricity to function (though the cost is literally pennies per day). So, if you’re storing firearms at a remote location with unreliable electrical power, or you need to locate your safe somewhere without a nearby outlet, choosing a desiccant-type dehumidifier might be better for you.
Where a dehumidifier is not practical, consider using desiccants
Today there are basically two categories of types of non-electric moisture-absorbing materials (desiccants) in common usage: silica gel and calcium chloride. Products like Damp-rid contain calcium chloride crystals that absorb moisture from the air and can be useful for drying out enclosed spaces or other areas after a flood or a broken pipe in your home. This can be relatively effective, particularly if you replace the containers regularly. The problem is that as the crystals absorb and then adsorb water (hold moisture on their surface), they eventually become saturated and then dissolve into a liquid brine. This slush of saturated crystals and brine must then be disposed of and replaced, and if it’s pretty humid where you live, this can get expensive. Additionally, calcium chloride and the brine produced is corrosive to metal, so few experts will recommend this type of desiccant material for use in close proximity to firearms.
For use inside a gun safe or storage locker/closet in cases where a plug-in dehumidifier isn’t practical, a silica-gel-based dehumidifier or desiccant canister can be helpful. There are also so-called rechargeable silica-gel devices like the EVA-DRY dehumidifier. Both types of silica dehumidifiers use silica gel beads to absorb moisture from the air, and one key point is these devices work without needing to be plugged in. Once the gel beads absorb enough humidity from the air, they need to be replaced or dried out and renewed for continued use.
The EVA-DRY type includes a visual indicator letting you know when the silica beads are saturated and need to be recharged or renewed, which involves removing the device from your safe and plugging it into an outlet for a few hours to heat the silica beads and drive the absorbed moisture out. Canister-type silica gel desiccants can be placed in a low oven to remove excess moisture in a similar fashion. After the moisture is driven out of the silica gel material, the device can be returned to the safe to continue working at absorbing excess humidity. (Note: You should never leave this type of desiccant dehumidifier plugged in all the time.)
Apply protective coatings
Regardless of whether you use an electric dehumidifier, silica gel desiccants, or a combination of the two, to maximize the protection of your firearms, you should apply appropriate coatings on the metal and wood surfaces before storage. Consult your owner’s manual, but in general, metal surfaces should be properly cleaned and then wiped with a quality gun oil or surface protectant. Many people find wiping guns with a soft rag dampened with any good-quality oil to be sufficient for preventing external oxidation, but others prefer dedicated rust-preventers like Eezox, Corrosion-X, or WD-40 Specialist Corrosion Inhibitor (don’t use regular WD-40, as it can gum up the internals of a gun if not cleaned out regularly). Be sure to read and follow all directions when using these chemicals, as some are potentially harmful to the lungs or skin. Also be sure to test them before applying to plastic or wood finishes, which may be damaged by some formulations.
For long-term storage, particularly for heirloom firearms, a good coating of Renaissance Wax or Flitz Rifle, Gun, & Knife Wax can prevent rust and help protect against fingerprint marks. A coat of quality wax also helps prevent wood stocks from drying out and cracking.
Inspect your firearms regularly
It’s important to check on your firearms regularly when in storage. How often you inspect them will depend on multiple factors, including your personal schedule, the humidity in your area, and whether or not you are opening and closing your safe often to access firearms daily, such as for a CCW pistol. Set a reminder on your favorite calendar device and make sure you check all the areas of your safe for signs of humidity (particularly if it’s crammed full, you lucky dog).
We recommend starting out by checking once a week, and if you find no evidence of excess (or insufficient) humidity after several weekly checks, you can consider moving to a bimonthly or monthly inspection routine, assuming everything continues to look okay.
Remember that every firearm you touch with your bare hands should ideally be wiped down with an appropriate soft cloth and protective solution to remove the acidic oils from your skin.
Store your firearms properly
In most cases, experts recommend not storing firearms inside padded gun cases or even in sheepskin pistol rugs. This type of storage material can actually retain unwanted moisture and keep it in contact with the surface of your gun, causing damage that wouldn’t have occurred if firearms were stored in the open (and properly dehumidified) air inside your safe. Additionally, oils or chemicals in the materials of a padded firearm case might react with the combustion residue or cleaning chemicals present on the surface of your gun and cause corrosion or staining. However, high-quality, silicone-impregnated gun socks can be useful for preventing dings and scratches to firearms that are stored in close proximity to one another inside a crowded gun safe, and may be useful in preventing rust and corrosion. Firearms stored in this manner should still be regularly inspected, however, and perhaps even more regularly than those stored outside of gun socks.
The best place to keep guns secure and stabilize humidity levels is in a gun safe
Most of the US population lives in areas with greater than 50% humidity levels. However, even if your home isn’t climate-controlled, the inside of your gun safe can be. A quality US-made gun safe doesn’t just keep your firearms and valuables secure from theft, fire, and unauthorized access, but it can be a refuge from high humidity levels if you use a hygrometer and a safe dehumidifier. If you don’t protect your valuable firearms from humidity, eventually they will just rust away to nothing. So if your guns are just leaning up against each other inside a closet or somewhere similar, consider investing in a good gun safe soon before it’s too late.
*Made in the U.S.A. from U.S. and Global Parts.
