I wanted a rust-proof finish on my khukuri. The cheapest and easiest solution I came up with is parkerizing.
Wikipedia: “Parkerizing (also called phosphating and phosphatizing) is a method of protecting a steel surface from corrosion and increasing its resistance to wear through the application of an electrochemical phosphate conversion coating.”
This process is used mainly on military type guns. The result is a dull gray finish which protects from rust and keeps oil on the steel. Abrasion will be an issue on a knife, but I already had the solution, and the amount of work required is minimal.
I ordered a manganese parkerizing kit from Shooters Solution, which can also be bought from Brownell. Our process will thus be mechanical only, since no electricity is used.
Step one is to clean the knife thoroughly with dishwasher liquid to remove any trace of oil. This is an important step, not to be skipped. The kit contains a special cleaning solution, which would be used after sandblasting, to clean and warm up the piece. I was out of this product, and used hot water instead.
Sand-blasting comes next, to remove any remaining oil and abrade the surface to make the manganese acid solution work better on the bare steel. The blasting cabinet we used had a very fine abrasive powder in it, which didn’t quite work, but a hand-held gun with coarse sand did the job quickly. At this time, it is very important that you do not touch the steel with your fingers! This would immediately start rusting and result in an uneven finish appearance. Flash rust will appear within ten to twenty minutes, so you must have your parkerizing solution and accessories ready nearby. I did see some on the blade, and it did create some differences in color. I didn’t care too much on a work knife, but the same result on a collectible gun would mean re-doing the whole process. Blast until you get a uniform light gray finish free of contaminants.
Be smarter than me and wear a mask and eye protection for sandblasting. My throat was itching after only a few minutes outside, blasting. That was a stupid idea!
The manganese solution comes concentrated in a bottle. You mix it with distilled water. A second cleaning after sandblasting is necessary, and it is a good idea to warm up the piece, so that the acid bath temperature doesn’t drop too low when you plunge it in. The ideal temperature is about 190F. If you don’t have a thermometer, you could wait for it to start boiling (212F) and immediately turn the heat off. Parkerizing only works on mild steel, and this is why you must use a stainless steel container. Otherwise, your solution would be wasted quickly, as any steel container would be also parkerized.
Make sure you do not touch the piece, and put it entirely in the solution. I wouldn’t do this because the knife was too long, and it resulted in a visible line near the handle, which again isn’t a big deal on a work knife. You will get much better results however if the part is entirely submerged. By the way, don’t breathe the fumes! Leave the part in for about ten minutes, moving it a bit once in a while. After removing it, clean it with hot water, and let it air dry. You can then apply the finishing oil. Et voilà! That’s all there is to it.
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