I have had several people ask me to explain the salt bath nitriding process that several rifle and pistol barrel manufacturers utilize.
By now, most of us have noticed rifle barrels with coating descriptions like Melonite, Ni-Corr, Black Nitride, or Salt Bath Nitride on everything from low-end semi-autos to high-end bolt action rifles. They are all variations of a surface treatment formally known as “Liquid Salt Bath Ferritic Nitrocarburizing Non-Cyanide Bath,” but more commonly referred to as FNC. Or just plain nitriding.
The FNC process dates back to the 1940s in Germany and England. It was a cyanide-based process that is hazardous to the environment and those working with it. By the 1980s, the process had been refined and cyanate replaced cyanide, which made the process much safer. The process still works the same and first was used on firearm barrels by Glock. It is known as Tenifer in that company’s nomenclature.
It is a heat treatment process that is done through immersion of the barrel in a molten salt bath that is heated to 900-1,200 degrees F, depending on the steel type, time run and case depth required. The normal temperature for steel used in the gun industry is 975-1,100 degrees F. The process uses cyanate salts to dissolve nitrogen and carbon into the steel, forming a two-part surface layer — an iron nitrate layer and a nitrogen diffusion layer that gives a hardened surface without hardening the core.
Increased barrel life, increased corrosion resistance, uniform color (both inside and outside of barrel become black), an increased velocity and lower chamber pressures due to less friction, are some of the benefits of the process. There was also a reduced need to lubricate due to the lubricity the process creates, resulting in less dirt sticking to the lube on the rifle.
The process is much more corrosion-resistant than hard chrome, which is still the standard lining of AR-platform rifles. Another advantage over chrome linings is that they are difficult to apply evenly, and the bores of rifles that are to be chrome-lined have to be bored a little larger than the desired specifications.
The FNC process is not a lining but reacts with the metal of the barrel both inside and outside the bore to harden the barrel. The only way to remove a properly nitrided treatment is to remove the metal.
Most of the manufacturers who produce AR platform rifles have been looking hard at the FNC process for their barrels and possibly the moving parts. In one test of an AR-15 rifle with a nitrided barrel in 5.56 caliber by several companies, there was no loss in accuracy and no measurable throat wear after 30,000 rounds.
However, nitrided barrels have not been in production long enough to make definite statements about how many rounds it would take to wear down a barrel that has been treated with the FNC process. But it seems to be at least twice as many as chrome-lined barrels.
Nitriding won’t put chrome-lined barrels out of business. The “don’t fix it if it isn’t broke” folks who love their chrome-lined barrels will keep buying what they like.
In the future, I believe we will see more firearm manufacturers start offering FNC-treated barrels in their top of the line firearms to the public as buyers become aware of the advantages of nitriding.
At about $89 a barrel, it makes sense to give the customer a choice.
Smokey Merkley was raised in Idaho and has been hunting since he was 10 years old. He was a member of the faculty of Texas A&M University for 25 years. There he taught orienteering, marksmanship, self-defense, fencing, scuba diving and boxing. He was among the first DPS-certified Texas Concealed Handgun Instructors. He can be contacted at email@example.com.