what the... rusty blade coatings? explain please?

G

goodshepherdknives

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Apr 7, 2013
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Hello, ive had a few rusty blade coatings and i was wondering if anyone knew what caused thick brown orange rust overnight with no moisture being a regular part of the materials regular touch, and also the bare metal is fine.

here is the first. crkt m16 14-d desert big dog tanto. love this knife. rusty.
IMG_20130928_085251_156_zps2624fd7d.jpg


here is a tool i have. brand new, shiny
IMG_20130928_085237_253_zps668e745e.jpg
. two weeks... this.


now this is the reason why i posted this. i have this blur and i cut a lemon today. i squeezed it in some water, then wiped the blade off. the edge is fine. i tried to brasso it and no luck.

IMG_20130928_084601_248_zpsaa02b732.jpg


anyone else have this problem or find a way to fix? can anyone scientifically explain? thanks for reading
 
well the lemon part is easy
we all use a vinegar wash for old rusty blades
its acid, it eats the oxidation
makes it easy to remove
the rest is just a fact of H2O plus IRON =ferrousoxide also known as RUST
 
but the point of a coating is to resist rust. it covers the steel. which is stainless. which resists rust. which has constantly been dry. the edges are not corroded at all. just the part thats supposed to resist rust
 
goodshepherdknives said:
but the point of a coating is to resist rust. it covers the steel. which is stainless. which resists rust. which has constantly been dry. the edges are not corroded at all. just the part thats supposed to resist rust
Click to expand...

Not true. The point of the coating is called "light discipline", meaning preventing reflection of light.
 
RevDevil said:
Not true. The point of the coating is called "light discipline", meaning preventing reflection of light.
Click to expand...

Very true, at least for DLC. However, Benchmade offers knives with Cerakote coating that I believe is for rust/stain prevention. So not all coatings are useless for rust prevention.
 
I have gun oil i can use. i have never had a blade rust, only the coating. titanium and tungsten dont corrode easily, so i again dont understand how its possible to have iron oxide on a coating that is not iron based. if coatings are not to prevent corrosion, why does for example cold steel use a black powder coat on their 1055 non stainless machetes for the purpose of in their words protecting it from corrosion, when the edge, not the blade or coating, is rusty when neglected. or ka bar using a black epoxy powder finish. never any problems when wet or neglected. it is to protect a high carbon steel blade from rust, as is my psycho 711, benchmade nimravus, it goes on. everyone replying is seeming to think i need to add oil to prevent rust, on knives that are never wet. im confused.
 
Invective said:
Very true, at least for DLC.
Click to expand...

show me from the manufacturer website or other sources these words. ive never heard this before in 12 years of collecting, and sharpening and researching knives that a coating is not applied with *only* light/glare reduction and *no benifit* to corrosion resistance. especially when the exposed and bare metal is still polished. my tungsten wedding band is not corroded and yet the tungsten DLC is. why is this seemingly normal to everyone
 
Remember that stainless steel is just that, stain less not stain proof. If it has carbon in it which all blade steels do it will rust if not cared for.

I use a liquid wax for covering blades and lubing the pivot in folders.

I found this brand from sharpening scissors, its a pivot lube and rust inhibitor.

"Disclaimer" I also sell it and find that it works far better than any oil because of oil picking up every piece of lint and dirt in your pocket etc.. Wax doesn't do that, so the blade and pivot stay cleaner and operate smoothly.
 
goodshepherdknives said:
show me from the manufacturer website or other sources these words. ive never heard this before in 12 years of collecting, and sharpening and researching knives that a coating is not applied with *only* light/glare reduction and *no benifit* to corrosion resistance. especially when the exposed and bare metal is still polished. my tungsten wedding band is not corroded and yet the tungsten DLC is. why is this seemingly normal to everyone
Click to expand...

I don't have time to search for you, but Sal Glesser and Michael Janich both explained that the coatings used on many knives was not there to prevent rust. It was there to make the blade less "shiny" in an environment where that sort of thing was a priority. Another thing that mayinduce corrosion is body chemistry, oils and residue from your own body can react with metal. Most of the coatings on the knives you've posted are porous, and they do not in fact "seal the steel" 100%.
 
I don't know anything about coatings, but I know a few things about humidity. Even when you say the knives were 'dry' unless they are stored in a humidity controlled environment, they are only as dry as the air. My point being, I've had tools rust just sitting on my table.

Also, if you don't mind my attempt to guess whats going on, I would assume the steel is rusting underneath the coating? So the coating is not entirely sealing off the steel from all moisture?
(eta: What Rev said)
 
Rhinoknives1 said:
Remember that stainless steel is just that, stain less not stain proof. If it has carbon in it which all blade steels do it will rust if not cared for.

I use a liquid wax for covering blades and lubing the pivot in folders.

I found this brand from sharpening scissors, its a pivot lube and rust inhibitor.

"Disclaimer" I also sell it and find that it works far better than any oil because of oil picking up every piece of lint and dirt in your pocket etc.. Wax doesn't do that, so the blade and pivot stay cleaner and operate smoothly.
Click to expand...

wow diamonds and charcoal must be terrible rust magnets then if the carbon, not the iron in the steel is what causes rust ;)
 
r8shell said:
I don't know anything about coatings, but I know a few things about humidity. Even when you say the knives were 'dry' unless they are stored in a humidity controlled environment, they are only as dry as the air. My point being, I've had tools rust just sitting on my table.

Also, if you don't mind my attempt to guess whats going on, I would assume the steel is rusting underneath the coating? So the coating is not entirely sealing off the steel from all moisture?
(eta: What Rev said)
Click to expand...

yup i guess ill have to take the coating off of one small spot under the worst of the rust on my m 16 and see if its pitted. but why wouldnt brasso remove the rust...
 
The first picture of the M1614D looks like some gunk that was coating the blade that is now piled up and looking nasty on one side. It looks kind of like like what marine tuff cloth leaves behind. Clean it off, passivate ( get off any remaining stuff that can oxidize like dust from a sharpener or file that was used on non stainless, any acids, bases, or salt, or oxide particles itself down to just blade coating, or finish), then re seal the pores with oil, grease, wax, silicone etc. I see more gunk on that blade than rust. In fact I see only one small spot that might be rust.

second. The tool. You have actual rust. Sand it off, then do above steps.

3rd picture, the blur.

I don't see what you are talking about. You Brasso'ed it, OK. Why? Oh well. Clean it off, get the corrosive stuff off, relube .

I use silicone cloths from the gun cleaning section in the big box store. They are great for quick wipe downs of your knife AFTER you have washed the lemon juice off, the brasso, the salt water & fish guts, whatever.

Or, you can get clear liquid silicone as sold By A.G.Russell in his catalog or on his website. It's great stuff and I use it on my non stainless blades. Always get the corrosive stuff washed & cleaned off before lube, wax, oiling or coating your stuff.

Of the three pictures above the only one I see actual rust is the tool in the second picture. If there is something I missed I apologize but chances are it's something I can't make out as rust so how bad can it be?
 
RevDevil said:
Not true. The point of the coating is called "light discipline", meaning preventing reflection of light.
Click to expand...

Or to cover up tool marks made during the manufacturing process.

Moose
 
5 dollars... 30 wipes, each one can be used on multiple blades.. easy, fast, convenient, and food safe!

14205558120815075455.jpg

 
goodshepherdknives said:
Hello, ive had a few rusty blade coatings and i was wondering if anyone knew what caused thick brown orange rust overnight with no moisture being a regular part of the materials regular touch, and also the bare metal is fine.

here is the first. crkt m16 14-d desert big dog tanto. love this knife. rusty.
IMG_20130928_085251_156_zps2624fd7d.jpg
Click to expand...

Hard to tell from the pict but is your CRKT M16 tan or gray with bead blasted blade? The pic looks gray to me.
 
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