Rust on H1 !?

J

jps01

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Apr 22, 2006
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Actually I placed this post in some other thread, but I repeat it as a new thread because it might get overlooked there and as I would like to know your opinion and maybe Sal's opinion on what had happened to my H1 folder.

I have decided to take my Pacific Salt with me as a backup knife while scuba diving because I like the idea to have some Spydie with me also underwater. And because it's serrations are so sharp it may be really useful one day, hopefully not.
I am pretty happy with it.

But there is one place on the blade where I got rust on it almost immediately (3-4hours !!!) after first time scuba diving (brand new knife from the box) with it in the pocket of my jacket (BCD). It was the PACIFIC SALT engraving. Absolutely no signs of any rust anywhere else including other blade inscriptions.

Anyway I polished the rust off pretty fast using my toothpaste and covered with some silicone grease for future use - no problems anymore.
Can anyone explain me why rustless H1 gets so easily rust in the place of the factory engraving ?

In my opinion maybe this is the way the Pacific Salt saying inscription is performed on the blade, that makes it more rust prone than other places ??
It happened about 2 weeks ago, I dived in the caribbean in Atlantic (one certain explanation is I should have taken Atlantic Salt for this time :) :) :) ) and I opened the knife for checkup just after returning from the boat to my hotel (approx 3-4 hours from diving)
 
Residual metal from tooling bits is a possibility.... other metal dust, particles or residue from factory.....
 
Like Robert suggested, it's probably residuals from another material. But in general rust does occur at the more stressed areas of an ferrous object.
This is from a website I made last year:

"Oxidation occurs to some degree to most metals exposed to air. For instance, aluminum, whether in foil, powder, or billet form is always covered by a layer of aluminum oxide. Such oxidation is not catastrophic to aluminum because the oxide layer prevents further oxidation. Iron, the main material in both of the above objects, does not enjoy the same protection from iron oxide. However, the formation of an oxide layer on iron is not catastrophic, merely causing a darker appearance, as can be seen on arms and armor collections in museums. So clearly some other process is occurring in the service conditions ... that causes this extended corrosion.

The figure above [does not exist anymore] depicts a droplet of water on an iron surface. The droplet contains dissolved oxygen from the atmosphere. The oxygen undergoes the following reaction:

O2(g) + 2H2O(l) + 4e- -> 4OH-(aq) E ° (red) =0.401 V

At the same time, the iron undergoes the following reaction:

2Fe(s) -> 2Fe2+ (aq) + 4e- E ° (red) =-0.440 V

The potential difference for these two hall-cell reactions is 0.841 V, indicating it is a spontaneous reaction. Hence the droplet creates a miniature electrochemical cell which results in rapid pitting of the metal at the centre of the droplet.

The same process occurs when an iron object is immersed in water. At certain areas of the metal where there is strain in the crystal structure, the metal is more active in its tendency to become the anode. Electrons freed at these areas due to the oxidation reaction may travel along the metal to another area where the electrons are consumed in the reduction reaction. This electron movement accounts for the observation that sometimes there are heavy localized rusting in an object while in other areas the rust is surprisingly minimal in comparison."

*Edited per Lambertiana's comment
 
kel_aa said:
O2(g) + 2H2O(l) + 4e- -> 4OH-(aq) E °=0.401 V

At the same time, the iron undergoes the following reaction:

2Fe(s) -> 2Fe2+ (aq) + 4e- E °=-0.440 V

The potential difference for these two hall-cell reactions is 0.841 V, indicating it is a spontaneous reaction. QUOTE]

You got one of your half-reaction potentials mixed up. The potential for the oxidation of Fe(s) to Fe2+(aq) is +0.440V. Then your cell has a net potential of +0.841V.

This reaction is normally rapidly followed by the conversion of the Fe2+ to Fe3+ to make red rust, Fe2O3.
Click to expand...
 
I listed both E(naought)'s as reduction potentials. As you pointed out, I don't think that was clear, and prehaps misleading.
 
robertmegar
Residual metal bits from the factory... yeah,I didn't think of it. Next diving holiday hopefully in about 6-8 weeks, so I test the knife again then :) I'll remove protective silicone grease, to test if it get rust again or not.

kel aa, lambertiana
My fixed blade diving knives made of 420 also get rust at their engravings first.
Now I know more on what's going on in there
Thanks
 
On the subject of residual metal left by non-stainless tools on stainless steels - my brother did a lot of consulting work for the construction of the Spallation Neutron Source at Oak Ridge National Lab, and they were very strict about no carbon steel tools touching the stainless parts.
 
And not just carbon steel tools - on many equipment purchases no tools of any kind could be used that had previously been used on any type of carbon steel. This meant the manufacturers had to buy dedicated stainless steel tools to do the job.

This led to an interesting question one day when I was cutting plastic sheet off some equipment at the vendor's shop for an inspection, and one of the guys there asked if my knife was stainless steel (it was).
 
I've been thinking on this for awhile. H1 might be especially susceptable to rust formed from other metals on it due to a displacement reaction with the more reactive metal (our residual metal here, perhaps).
 
The Spyderco people" think it isn't rust.

In the few samples" we've seen, the color seen wasn't rust. usully some type of food. It is possible that something in the engraving might be discoloring, but I would guess it is a foreign element causing the color.

sal
 
on mine, whatever was in the engraving looked like gold. seriously, like gold filigree or powder. The letters "atlantic salt" were gold inside of them. whatever that was, it rusted. The rest of the blade? NADA. and the edge retention gets better every time I sharpen it. :)

pete
 
Hmm...I'm not familiar with something that oxidizes to gold color. But then, I'm a biologist.

Can we get some photos up in here?
 
Thank you for your feedback Sal !
Very pleased to meet you on Web - I admire the knives you make a loooot !!!
It looked rust-like to me, but obviously it could be sth different. I"ll give my folder another diving try in Aug, so if it showes again I take the pictures and maybe not clean it so quick, to make sure it doesn't tend to spread out from the engraving.
Aha, in my knife the engraving was just polished steel color - before it got rust (or whatever it was)
 
Iam glad my 4 day old pacific salt has a blank blade (sans the name that is), prod date 02/2005.
 
All we can think of is that there is something in the engraving process that is leaving a rust or similar coloring. We'll have to do some investigating.

Actually we're glad this came us so thanx for the beef. It helps us to understand.

We do believe that watever is happening, that it's not coming from the H-1.

sal
 
Do the current production Pacific Salt knives have the "Pacific Salt" and bug in black, or is it just "Pacific Salt" etched on like the older ones??? The name on my Pacific Salt looks laser etched into the blade, but I have seen pictures of them done in black with the bug on the blade?
 
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