Sorry guys, I don't want to beat a dead horse here, but there's still a bit of confusion and misinformation.
While it's true that Tenifer and Melonite, which are basically the same process, are surface hardening treatments, and penetrate into the metal (and correctly noted by some posters above as being different from surface finishes); these treatments can and do impart some coloration and a surface finish.
Notwithstanding that, other surface finishes may still be applied over the Tenifer. I've heard that Glock uses a Parkerized finish over the Tenifer- I can't confirm it. And I have no desire to own a Glock so I don't plan to delve into the subject.
Here's what two leading providers of Melonite type treatments say about the process (note- bold fonts and italics are my emphasis):
Coal Creek Armory Custom Finishing And Refinishing
Quote:
ISONITE QPQ™
Coal Creek Armory is proud to offer the ultimate black "finish" for your steel firearms - Isonite QPQ™.
Isonite QPQ™ is a thermochemical process (ferritic nitrocarburizing) used for the case hardening of iron-based metals. In a molten bath of special salts, nitrogen, carbon, and small amounts of oxygen are diffused into the surface of the steel, creating a super-hard surface, called the "compound layer." Additionally, small amounts of carbon are pulled from within the substrate, toward the surface, creating a "diffusion zone," which exhibits a gradient of concentration of carbon and nitrogen, decreasing toward the core. Thus, the process provides both a hardening of the surface, and a gradient alloying of the substrate, which improves the ductility and overall strength of the material.
Isonite QPQ™ can be used on both carbon steel and stainless steel. Melonized steel gun parts will be blue-black in color, and will exhibit surface hardness in the area of RC70, lower coefficient of friction/enhanced surface lubricity, superior running wear performance, superior sliding wear resistance, superior heat resistance, and superior corrosion resistance. The treatment penetrates to a depth of ~.004" to .008," with surface dimensional growth of only .0002" to .0004"(negligible), so post-treatment fitting is not a concern. Final appearance of the surface is dependent on the type of surface prep used, with surfaces tending to appear a bit smoother than before treatment. Thus, surfaces prepared via our preferred method of aluminum oxide blasting, which have a matte appearance, bear a smoother, yet non-reflective, satin post-treatment appearance. Polished surfaces tend to retain approximately the surface appearance they had prior to treatment. For those who love the look of a "tactical" black finish, Isonite QPQ™ is, without doubt, the best practical surface treatment available for firearms today.
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Melonite Processing
Quote:
The MELONITE� Nitrocarburizing Process
MELONITE is a thermochemical treatment for improving surface properties of metal parts. It exhibits predictable and repeatable results in the treating of low and medium carbon steels, alloy steels, stainless and austenitic steels, tool and die steels, cast and sintered iron.
Melonite Processing : Salt™ Bath Nitriding System
As the first job shop on the west coast to offer Melonite processing, Burlington uses its salt bath experience to diversify its servicing to the Southern California metal finishing industry. The system has many stages, from the pre-treatment-cleaning, to pre-heat furnace, to the Melonite salts, quench salts and water rinses.
Melonite Processing: Melonite QPQ
Melonite™ and Melonite QPQ™ are thermochemical processes intended for the case hardening of iron based metals. These processes are categorized as molten salt bath ferritic nitrocarburizing. During these processes, nitrogen, carbon, and small amounts of oxygen are diffused into the surface of the steel, creating an epsilon iron nitride layer (e - FexN).
A degraded form of this nitride layer (gamma prime: g' - Fe4N) is obtained during plasma or gas nitriding. The nitride layer is composed of two principle zones. Zone 1, called the compound or "white" layer, extends to a case depth of ~0.0004" to 0.0008". The compound layer is porous, which lends to the lubricity of the finish, and hard (~700HV to 1600HV). Zone 2, called the diffusion zone, extends to a case depth of ~.004" to 0.008".
In addition, small quantities of substrate carbon are pulled from deeper within the substrate toward the surface. The diffusion zone demonstrates a decreasing gradient concentration of carbon and particularly nitrogen as the gradient extends deeper into the surface of the substrate. This property yields a tough outer surface or shell, yet alloys the material to retain ductility, thereby lending to the overall strength of the material.
Resulting properties from these chemical and structural composition changes are increased surface hardness, lower coefficient of friction, enhanced surface lubricity, improved running wear performance, increased sliding wear resistance, and enhanced corrosion resistance. Naturally, the alloy of the substrate will influence which properties are principally affected and to what extent they are affected. 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
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So I doubt Glock puts any type of Krylon paint on their slides or any other type of industrial paint. Although some lazy Glock armorers might choose to do that as a quick cover-up.
Black Oxide would be a better choice as well as Parkerizing. I'd like to know if S&W adds any additional color treatment on top of their Melonite treatment.
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