...นี่ครับ
...My tenifer finish is wearing off how do I replace it?
The tenifer finish is an extremely hard surface preparation that is impregnated into the slide before the black parkerized coating is applied. Even if the black coating is wearing off, the slide is is still protected by the tenifer finish.
...What is the tenifer finish?
Surface hardening of steel and iron (to improve wear resistance) can be done by either allowing the surface of metals to react with either Nitrogen (nitriding), Carbon (carburizing), Boron (boriding), etc. TENIFER is termed for a chemical bath nitriding process whereby nitrogen is chemically released and introduced into the surface at a suitable high temperature to allow the chemical process to take place.
Using the liquid bath techniques, the temperature requires to activate the reaction is about 550 to 580 Celsius. The bath is performed in a molten, nitrogen-bearing liquid containing either cyanides or cyanates. However, cyanide-free liquid has also been used to release Nitrogen and then allow it to react chemically with steel (iron)at the surface (modern techniques).
Interestingly, when using the cyanide-free liquid, Tenifer is actually the salt bath nitro-carburing technique because it starts (first reaction) with Carbon-Nitride (CN) and allows it to react with Oxygen (0)to produce Nitro-carbon-dioxide byproduct plus Nitrogen. The simultaneous second reaction takes place when nitrogen (N) is in contact with Iron (Fe) to form FeN (iron-nidride).
The tenifer coating "composition" of Glock's steel slide is essentially that of FeN.
It is interesting to note that FeN coating is used mainly to increase the surface wear resistance to against galling and wear. The corrosion resistance is also better for iron and conventional steel that are NOT stainless steel. Most stainless steels need not to be nitrided. The reason is stainless steel has chromium to fight against corrosion and rust (this is why we call these material stainless). However, nitriding a stainless steel will almost always lower the corrosion resistance of the stainless steel. This is because the nitrogen will also react with some of the chrominum (Cr) at the surface of stainless steel to form Chrominum-nitride (CrN).
Obviously, gas-nitriding is a simpler process (but not necessary cheaper) to form a tough wear resistance coating. In this case, pure Nitrogen gas is chemically reacted with the metal such as iron (Fe) by holding the metal in the Nitrogen gas environment at high temperature allowing the chemical reaction to take place.
The true FeN (tenifer) coating has a dull-gray color surface. Definitely, never black. In some applications, FeN coatings can also be polished to give a bright metal finish appearance.
http://www.glockfaq.com/gunsmithing.htm 
