Extrema Ratio AMF Survival Knife
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| Wet all day in a hot humid rainforest environment, submerged for approximately 2 hours while exploring tannin stained freshwater pools, the Extrema Ratio AMF shows negligible signs of corrosion. |
Recently I took a knife labeled as a "Survival knife" from the manufacturer diving into warm tannin stained (Acidic) tropical waters for about just over 2 hours.
This knife is not a specific diving knife but I figured if you're going to call your product a "Survival Knife" then you had better be making a good product and if it's a survival knife then it needs to be not afraid of water!
I was not disappointed when I disassembled the knife at the end of the day. A burnishing, anti-glare finish had been applied to the entire blade surface. This is simply a physical finish. There is a trade off with corrosion resistance in stainless knife alloys; the higher the HRC the lower the corrosion resistance as the the amount of soluble Chromium present will be less than in equivalent alloyed steel at a lower HRC's. This knife was HRC58. Not too hard not too soft. Just right.
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| You can see some very slight staining on the blade, there was no pitting evident. The tang had been wet all day but no evidence of staining or pitting. The knife had been used to cut up many different jungle plants all of which contain sap of various acidity and very sticky too. The knife was used for diving in a fast flowing highly oxygenated river, stained with tannins (very acidic) for approximately 2 hours. There was no corrosion present in the small black threaded nut at the end of the tang either. For all other stainless fixtures (not made from N690) there was no evidence of corrosion. |
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