Corrosion testing with unexpected results. Why?

N

Naphtali

Joined
May 20, 2002
Messages
148
This information is anecdotal. I hope there is an reasonable explanation that does not include voodoo.

I have three Morseth laminated carbon steel sheath knives presently in use, plus one Cold Steel TwistMaster folding knife with Carbon V® blade. I live in west central Montana where annual rainfall is about 25-27 inches.

Until about ten years ago I had a MASSIVE phobia pertaining to rust/corrosion. Years before I had bought half-a-dozen TwistMasters on close-out @ $4.95 each delivered. I decided to verify the severity of corrosion of non-stainless steel blades in routine, regular use. At first I religiously cleaned and oiled the folder after every little use - and I mean EVERY. The blade discolored and mottled within a few days, then remained in that condition. I thought my babying the blade was retarding the test, so I stopped all maintenance except washing the knife after food preparation and wiping dry with a towel - that is, no oil or lubrication of the blade or hinge at all. . . . That was about 7.75 years ago. The blade hasn't further corroded. The only "maintenance" I do is to wipe/strop the blade along my pant leg a few times every few days, usually when I'm watching a DVD.

The Morseths have never received any lubrication or oil of any sort. I wash them after food preparation and dry them with a towel. They, too, discolored and mottled, then remained that way. This has gone on for four years.

The TwistMaster is EDC. The Morseths are kitchen cutlery and hunting/outdoor knives. Edges are free of mottle and have 15-degree edges that are sharpened in a fixture no more than once a year.

I guess I can report that my corrosion testing is still going on.

One blade as I describe I could accept as a freakish exception. Four blades for the length of time I've been "testing" their corrosion is way more than freakish. I have observed surface rust on others' knives and guns. And my interpretation of metallurgical information I have read appears to report my experience cannot happen.

What the heck is going on?

Why?
 
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Leave them out in the rain and see what happens..lol
But seriously, I think there is very little humidity in Montana compared to say east texas, where I live, but from my experience, carbon blade are not that bad at rust unless they are in constant contact with some form of water. Plus if they have developed a good patina, that will keep further rust to a minimum but not rust proof

I have an Ontario machete that is about 15 years old and had a good patina on it. It was left outdoors, under a covering, for the last 5 years, and had very little rust on it and I never cleaned it
 
I've seen machetes in tropical climes (Costa Rica, Micronesia) that were used/abused but still held up fine despite a light coating of rust/corrosion. Stick them in the rafters of a sugar house for several months and they hardly showed any change. In regular use, rust is rarely a problem for carbon steels.
 
Patina is the word I shall use in the future. I cannot understand why corrosion ceased at essentially none and remained at "essentially none" despite no preventive maintenance.
 
"I wash them after food preparation and dry them with a towel. They, too, discolored and mottled, then remained that way. This has gone on for four years."
Click to expand...

That's 99.9% of the battle. It's not difficult to keep a carbon steel blade from rusting significantly, if at all. The 'patina' that forms naturally on the blade will will also help with that. Much of what we read here about corrosion on non-stainless blades only serves to feed an irrational level of fear about it. Just using the blade, cleaning it after use and putting it away dry will render moot most of the 'hype' about rusting issues.

Corrosion tends to creep back into the picture if/when a knife is neglected for a while and we're 'not looking', leaving it a little dirty (salts from the hands, food acids and chemical exposure can really accelerate rust) and/or in an environment that fosters rusting (high humidity for extended periods of time, or exposure to caustic fumes/vapors). For most conscientious people, just handling and using the blade regularly will be enough prevention, because we'll always see if it's dirty or wet, and immediately correct it before putting the knife away, purely out of good habit. Knives that get put down during use & misplaced, or just forgotten for a length of time, are usually the ones that have problems.


David
 
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I'll repeat the above - with carbon steel it is most important to wipe them dry after use, failure to do this once and not use the blade for a few days will result in rust forming.

Most of my carbon steel knives are fixed blade, I keep them in hard waxed leather or waxed leather liner in Kydex shell. I also carry some of them IWB and have no problems with rust even in the Summer months Upstate NY. Only when it comes to storage for a long period of time will I bother to oil them, though on top of the wax residue from the sheath, is more or less overkill.
 
In my opinion carbon steel has a wonderful ability to take care of itself once a patina is formed. That is not to say that you don't need to keep it clean and dry (which really doesn't take much). Years ago I switched over almost all my knives to carbon steel and I like the way it performs and how easy it is to maintain. A few strokes on an Arkansas stone or a diamond plate and it's back to work. I spend much more time worrying about my guns, gunsmithing tools and reloading equipment out in the shop than my knives.
 
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