Small knife rust resistance experiment

HawkeyX · **Reply #30 on:** April 13, 2011, 11:50:45 AM

Cheers.
Didnt get home with the sunlight today so will hold off until the weekend to show latest developments...

HawkeyX · **Reply #31 on:** April 17, 2011, 12:30:12 PM

So, a week has gone by with both blades in the salt water. The results are not quite as I expected...
The long term salt blade increased in rust a bit:

However, the one that used to be in the fresh water:

Its still perfect! - not a sign of rust at all.
Interesting.
Now I cant be sure which is from what, but if you look at the nail nick's, they are different sizes, suggesting different ages of the swiss knives they came from. I can confirm 100% one is from a Tinker and the other 99% from an non hook Climber (with older corkscrew).Perhaps age, or stainless used at the time has caused one to rust and the other not to...thoughts?
So, no content bringing the mountain to moses, I decided to take moses (the blades) to the mountain (the sea). This is either the next stage of the rust test, or, a fairwell to the brave blades of science:

I chose a place you can only access at low tide, but who knows, a scavenger may find them and take them.

So...its either an update next week, or...

nsa-x-file · **Reply #32 on:** April 17, 2011, 12:33:13 PM

Love those photos by the water.

Looking forward to the update.

Gareth · **Reply #33 on:** April 17, 2011, 06:11:59 PM

Very interesting that the second blade didn't rust at all. Other than being a different steel can anyone else think of a good reason for this?

jekostas · **Reply #34 on:** April 17, 2011, 07:40:53 PM

Quote from: Gareth on April 17, 2011, 06:11:59 PM

Very interesting that the second blade didn't rust at all. Other than being a different steel can anyone else think of a good reason for this?

Age and wear. My guess is that the unrusted blade is newer with less wear - less pitting and scratching on the surface, considerably less surface area for rust to form in.

Similar reason to why mirror polished blades are more corrosion resistant than bead-blasted or matte-finished blades of the same steel.

AimlessWanderer · **Reply #35 on:** April 17, 2011, 07:54:53 PM

Quote from: Gareth on April 17, 2011, 06:11:59 PM

Very interesting that the second blade didn't rust at all. Other than being a different steel can anyone else think of a good reason for this?

Salt water is WAY more detrimental to the steel. Going back to the boat subject and anodes - if you use freshwater anodes at sea - bye bye anodes VERY quickly, whereas salt water anodes don't corrode in fresh water and thus don't protect the boat. Don't worry - you'll see some rust now it's been put to sea assuming the water (or anything else) doesn't take it first

... but yes, the scratches/wear arguement is relevant too, just less so than the electrolyte in this instance

Gareth · **Reply #36 on:** April 17, 2011, 08:47:07 PM

Quote from: jekostas on April 17, 2011, 07:40:53 PM

Quote from: Gareth on April 17, 2011, 06:11:59 PM
Very interesting that the second blade didn't rust at all. Other than being a different steel can anyone else think of a good reason for this?

Age and wear. My guess is that the unrusted blade is newer with less wear - less pitting and scratching on the surface, considerably less surface area for rust to form in.

Similar reason to why mirror polished blades are more corrosion resistant than bead-blasted or matte-finished blades of the same steel.

except of course that it's the non-rusty blade that's got all the scratches. In fairness I'd normally completely agree with you.

HawkeyX · **Reply #37 on:** April 17, 2011, 10:28:29 PM

Yes, the non rusty blade had many more visual scratches than the non rusted. Also, the non rusted was in the same salt conditions for a week as the rusted and didnt show any rust at all, even though the first blade in salt got obvious rust in the first week.
In the controlled jar, the rust from the blade being exposed to air/water showed no more rust at the surface level than that which was submerged all the time (the tip)
I would assume the non rusted is newer, and obviously pitting etc on the older blade can be smaller than seen by the naked eye, but you would have thought visual scratches were just as detrimental as unseen pitting?
Also related to that, would the cutting edge not be one of the first expected areas to rust? - its not polished to the degree that the blade is.
Can anyone approximate the ages of the blades based on the nail nicks?

AimlessWanderer · **Reply #38 on:** April 18, 2011, 12:57:24 AM

Quote from: HawkeyX on April 17, 2011, 10:28:29 PM

Yes, the non rusty blade had many more visual scratches than the non rusted. Also, the non rusted was in the same salt conditions for a week as the rusted and didnt show any rust at all, even though the first blade in salt got obvious rust in the first week.

I thought the non-rusted had always been in plain water - first fully submerged then partially

Quote from: HawkeyX on April 17, 2011, 10:28:29 PM

In the controlled jar, the rust from the blade being exposed to air/water showed no more rust at the surface level than that which was submerged all the time (the tip)

That did surprise me - certainly very different from what I've seen before. But that was over FAR greater periods of time and not on stainless knives

Quote from: HawkeyX on April 17, 2011, 10:28:29 PM

I would assume the non rusted is newer, and obviously pitting etc on the older blade can be smaller than seen by the naked eye, but you would have thought visual scratches were just as detrimental as unseen pitting?
Also related to that, would the cutting edge not be one of the first expected areas to rust? - its not polished to the degree that the blade is.
Can anyone approximate the ages of the blades based on the nail nicks?

I'd have expected that too - lots of surprises so far

Lets hope they're both still there next week

HawkeyX · **Reply #39 on:** April 18, 2011, 02:30:44 AM

Quote from: 50ft-trad on April 18, 2011, 12:57:24 AM

Quote from: HawkeyX on April 17, 2011, 10:28:29 PM
Yes, the non rusty blade had many more visual scratches than the non rusted. Also, the non rusted was in the same salt conditions for a week as the rusted and didnt show any rust at all, even though the first blade in salt got obvious rust in the first week.

I thought the non-rusted had always been in plain water - first fully submerged then partially

Sorry for the confusion. I placed the fresh water one in salt water with the other blade last week.

Fingers crossed the blades survive the wilderness. Would be great to see how the non rusted goes over a week!
Stormy conditions at the moment however, so will have to wait and 'sea'

KiwiMark · **Reply #40 on:** April 18, 2011, 01:23:42 PM

Quote from: jzmtl on March 30, 2011, 06:53:05 PM

So.... Which is more corrosive, sea water or vegemite?

Well, the Vegemite would be more salty . . .

Damn, now I have a hankering for some Vegemite - time to make some toast!

Cyclone82 · **Reply #41 on:** April 18, 2011, 01:47:26 PM

Ha Vegemite again

. I actually just had a Vegemite sandwich 20 minutes ago, something i haven't had in a long time!

This is going to be real interesting to see how they go being left out in the sea. such a good idea

I would have thought the metal is the same make up throughout so it would not matter if there was scratched or not. Theres no coating so i dont think scratches would rust any more.

AimlessWanderer · **Reply #42 on:** April 18, 2011, 04:43:09 PM

Quote from: HawkeyX on April 18, 2011, 02:30:44 AM

Quote from: 50ft-trad on April 18, 2011, 12:57:24 AM
Quote from: HawkeyX on April 17, 2011, 10:28:29 PM
Yes, the non rusty blade had many more visual scratches than the non rusted. Also, the non rusted was in the same salt conditions for a week as the rusted and didnt show any rust at all, even though the first blade in salt got obvious rust in the first week.

I thought the non-rusted had always been in plain water - first fully submerged then partially

Sorry for the confusion. I placed the fresh water one in salt water with the other blade last week.

Sorry - must have missed an episode. I'm back on track now

HawkeyX · **Reply #43 on:** April 22, 2011, 07:29:02 AM

Update time!

So I managed to catch low tide today and wandered down to the secret cove of the blades...
I forgot to take my camera, but was also 50/50 they would be there. About 30m away from the spot I saw a shimmering light that could only be a swiss blade (well, ok, any shining metal).
On close inspection, both blades are doing pretty darn good. The rustless one finally has a small rust stain, but this is at the pivot point, under the fishing line holding it there.

So they are holding up very well to the ocean so far (and are still there!). I'll try to get a pic before easter is over.

Quote from: Cyclone82 on April 18, 2011, 01:47:26 PM

I would have thought the metal is the same make up throughout so it would not matter if there was scratched or not. Theres no coating so i dont think scratches would rust any more.

Im no metallurgist, but thats a good point. I guess the only difference would be areas that are not as finely polished (e.g. bade edge), but so far neither scratch or cutting edge is showing to be any less resistant than other areas.

HawkeyX · **Reply #44 on:** April 24, 2011, 07:51:23 AM

Just managed to catch the tide before sun down today.
Both blades still hanging around, both doing pretty good after a week in the ocean (sorry for the amount of noise in images, had to use a fairly high iso!):

As in last post, only the small bit of rust stain on the pivot point of 'non rust' blade. Rust blade is looking no worse than several weeks ago.

Zag · **Reply #45 on:** April 24, 2011, 09:30:20 AM

This is such a great thread

If now the pivot point is rusting it would kind of back up the theory that high friction/use area rust faster. Or it would prove that rust is completely random

J-sews · **Reply #46 on:** April 24, 2011, 03:37:06 PM

Wow, this is an amazing test.

After seeing how quickly rust developed during the submerged-in-salt-water-jar test, I expected we'd see a lot more rust by now on the blades tied to the oceanside rock. These results so far are most surprising.

HawkeyX · **Reply #47 on:** April 30, 2011, 02:23:34 AM

So another week update.
I only just caught the tide again today and initially could only see the fishing line and not the blades. Luckly they had just tucked behind the rock and have survived another week.
So hows the rust going? - lets see:

Not bad at all!!!
Im going to give them one more week in the ocean and then bring them home for some closeups and to see how well I can clean them up again.
Might be time for a fuller experiment to be formed me thinks

Gareth · **Reply #48 on:** April 30, 2011, 10:02:48 AM

It's a good question, not only how widespread the rust is, but how deeply has the rust taken hold?

J-sews · **Reply #49 on:** April 30, 2011, 01:24:12 PM

AMAZINGLY little corrosion for the environment and length of time those blades have been exposed to it.

Heck, I can still see your reflection in the second photo!!

Top-Gear-24 · **Reply #50 on:** April 30, 2011, 02:54:57 PM

This is such a great topic

.

And I think the small knives are doing an amazing job, impressive results

.

(next test with some Leatherman knives ... ?

)

HawkeyX · **Reply #51 on:** April 30, 2011, 10:37:04 PM

Without getting close up yesterday, I think the only potentially bad rust is on the tip of what was the salt blade. Im pretty sure the rest will polish off next week (but we will have to wait to find out). I have an alright closeup lens, so will make sure I get pics.

I'd be happy to do a Leatherman test, but I only own a Juice and Squirt and dont want to experiment with them lol. (donations accepted

)

Related however, I do plan to up the ante with another Vic test. I just need to gather all the pieces and finish this one before I reveal it!

Malarauko · **Reply #52 on:** May 01, 2011, 12:25:10 AM

The metal quality must be pretty good. Those blades are holding out fantastically.

HawkeyX · **Reply #53 on:** May 17, 2011, 09:50:10 AM

Been a bit busy of late, but finally have got around to the update.
So as usual, waiting for low tide I made my way down to the 'spot'

As with every other time, I was happy to see the blades were still there, not stolen or swept away by the tide (we had a particularly big storm the week leading up to collection)

If anything, they almost looked better than the week before I think!

So thats the end of their venture at the beach. Before closing this section of the test and moving onto bigger experiments I will find some time in the week to take some closeup shots of the blades as they are, plus see how good I can clean them up

MultiMat · **Reply #54 on:** May 17, 2011, 01:17:28 PM

This has been a great experiment , thanks mate

nsa-x-file · **Reply #55 on:** May 17, 2011, 01:37:48 PM

Great info. Thanks.

Mr. Whippy · **Reply #56 on:** May 17, 2011, 05:16:34 PM

What an eye opener!

Great experiment.

Gareth · **Reply #57 on:** May 17, 2011, 06:27:08 PM

Does the term 'stone washed' apply here?

HawkeyX · **Reply #58 on:** May 18, 2011, 11:16:18 AM

so a few more up closer pic's. Not the best sorry, bad low lighting...anyway:

Interesting to note, the former fresh bade suffered most where the line was tied to it(but the other blade didnt). The former salt blade got a slightly raised area where it was rusting in the very first week of the experiment, but didnt get worse, whilst part of the cutting edge really suffered.
Both still cut fairly well!
Ill see how well I can clean them up over the next week.

Malarauko · **Reply #59 on:** May 18, 2011, 05:29:30 PM

Its fantastic to know that SAKs can stand up to so much. Those blades are going no where in a hurry.

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