
We’ve all heard the stories that GLOCK’s miraculous metal finish is impervious to any corrosive agent. It’s so strong that it’s actually illegal in the United States! Or so the story goes!
Here are the facts:
After some research, I found that one German company owns the various trademarks (Tenifer, Melonite and Tufftride) to a ferritic nitrocarburizing (not to be confused with carbonitriding or just plain carburizing) process widely used in industry to “increase surface hardness, lower coefficient of friction, enhance surface lubricity, improve running wear performance, increase sliding wear resistance, and enhance corrosion resistance,” according to Burlington Engineering Incorporated, a Southern California metal finishing service.

Apparently, Burlington and another company, KC Jones Plating (calling the process “NitroMet”), both use Kolene Corporation equipment and chemicals to apply this finish right here in the USA. Another process called “Nu-Tride” is another word for the exact-same finish exhaustively explained and analyzed on this finishing.com site.
Burlington Engineering states that it is a “leader in the application of quality Melonite* Molten Salt Bath Processing, an environmentally friendly high performance alternative to plating for corrosion resistance industrial rust removal.
Melonite is the most widely-specified process in the world for improving the wear and corrosion properties of metal and metal components. No process can match it for precise, repeatable results; no competitive technology offers two unique combinations of performance, versatility and cost-efficiency.
*Melonite was developed by Degussa Durterrit.”
Although misspelled on the Burlington website, this leads us back to HEF Durferrit, the Mannheim company that developed the process and probably does or did GLOCK’s work. Their website tells us that ”To meet the growing needs with regard to wear and corrosion resistance, as well as the enhancement of the fatigue strength, great efforts were devoted to the development and launching of the TENIFER® process, which is also known worldwide under the trade names of TUFFTRIDE® and MELONITE®. This nitrocarburizing process has undergone continuous development with regard to its regenerability and ecology, and from year-to-year the number of applications is increasing on all 5 continents.”
Elsewhere on the German site we read that “The term nitrocarburizing means an enrichment of the surface layer of ferrous materials with nitrogen and a small amount of carbon. This thermochemical treatment improves the wear resistance and the fatigue strength.
Used with a strongly oxidizing cooling bath – TENIFER®-QPQ – wear and corrosion resistant surfaces with an attractive black appearance are produced.
Products used in nitrocarburizing
- TF1 cyanide-free top-up salt for TENIFER® baths*; used for treating ferrous materials. Used only in combination with the REG 1 regenerator. Working temperature 480 – 630°C.
- REG 1 environment-friendly, nontoxic regenerator for TF 1 baths
- AB 1 oxidative salt for cooling parts treated in TF 1 baths; greatly enhances the corrosion resistance (TENIFER®QPQ process). The well-known traditional Durferrit NS salts are still available*.”
So we may assume that “traditional Durferrit NS salts” were probably the ones that the EPA had a problem with and started the truth-based legend that Tenifer could not be done in the US. Also here we learn that GLOCK probably uses the highest-quality QPQ variant of the Tenifer process. QPQ stands for Quench-Polish-Quench.
The Kolene site describes the QPQ: ”Ferritic Nitrocarburizing is a thermochemical diffusion process which imparts marked resistance to wear, corrosion, and fatigue in ferrous metal components. The optional quench / polish / quench adjunct treatment provides a cosmetically pleasing, black lustrous appearance, as well as a further improvement in corrosion resistance.”
Back on the Burlington site we learn the differences as we go up the scale of quality: ”The following chart demonstrates what properties are best enhanced by varying the Melonite process:
Melonite Processing: Melonite Q
- Improved Wear Resistance
- Improved Running Properties
- Increased Fatigue and Rolling Fatigue Strengths
- Heat Resistance
- Black Color
Melonite Processing: Melonite QP
- lncludes the properties of Melonite Q
- Lower coefficient of Friction
- Decreased surface roughness
Melonite Processing: Melonite QPQ
- lncludes the properties of Melonite Q and QP
- Low Light Reflection
- Further Decreased Coefficient of Friction
- Enhanced Corrosion Resistance (Not suitable for stainless)”
This last note probably explains the well-reported rust problems that Smith and Wesson M&P have had with slide corrosion. GLOCKs also have infrequent rust issues. The discussion on this Metal Finishing forum educates us to the fact that even the exact same finishing process is going to vary according to the details of the particular process. So inconsistancies even within one manufacturer should not be surprising.

Also, the process can be altered by time and chemical density as reported in this very scientific paper entitled: How different steel grades react to a salt bath nitrocarburizing and post-oxidation process: Influence of alloying elements. (Which you can’t read without paying for it, but you can view some cool SEMs like this.)

So there is my official scoop on Tenifer. It is an awesome finish. It is one of the best. It is not perfect, but carefully done, it can be close. GLOCK did not invent it, nor was it the first to use it. GLOCK may have been the first to use it on a firearm, though. The process is not secret, although they’d like to keep it mysterious. Other firearms companies use it, but apparently the cheaper version or inappropriately (on stainless steel, for example). In the past, it may have been prohibited by the US EPA, but now it is commonly applied in the US, even in Southern California, no less.

GLOCK's tough finish has changed its appearance over the years. Here you see the original dull oxide look. This finish can wear and scratch off with no harm to the tenifer under it. Later models are shinier and the glossy prep does not wear off as easily.
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