Spyderco Forums

I oil all my knives with 'dry silicone lube and generally don't have problems with minor corrosion or staining. (K390 has been fine for me, and is less stainless than Cru, no? It's has nice patina, but never rust)

Within my first couple carries, my cruwear ayoob developed the pits seen in the pics below. I cleaned the blade with BKF and re-lubed, and re-re lube semi frequently now, but the pits consistently grow rust spots while the rest of the blade is fine.

The pits are small but can be felt with a needle as physical depressions into the blade, NOT just surface staining. Material is missing.

Seems to me like a few grains of the steel are particularly reactive / oxidizeable.

What can be done, if anything, to discourage the pits from being a rust catalyst while the rest of the blade remains semi-stainless?

I cleaned the knife a few days ago so there is no rust visible, but the pits are visible.

I suspect cross contamination from the belt used to shape/sharpen the blade. I use cru-wear in the tropics and it is surprisingly (and pleasingly!) corrosion resistant - in my experience better than VG10 by miles which is a stainless steel.

I don’t think there’s any simple way to rectify cross contamination short of physically removing the contaminant, although I have been known to be wrong on occasions (usually when talking to my wife ). On the one knife I had this on I just ground the area with a diamond plate, which wasn’t pretty but did get rid of it.

*edited for early morning grammar.

Once you have pitting it will just keep getting deeper; that’s the pernicious thing about pitting.

Another thing I will add about the “cross contamination” thing. It doesn’t have to be a different steel. Ground particles from the same steel will accelerate corrosion if they are not fully removed. “Passivation” with acid helps to remove the particles.

Larrin wrote: ↑

Mon Apr 15, 2024 9:04 am

...
..It doesn’t have to be a different steel. Ground particles from the same steel will accelerate corrosion if they are not fully removed. ...

Very interesting, totally did not know that. Learned something new, thanks!

Larrin wrote: ↑ “Passivation” with acid helps to remove the particles.

Thank you very much for the insight Larrin et al. Can I do an at-home passivation to mitigate this?

If I can, do you have a recommended brew or method you could describe or link me to?

Thanks again!

Nitric acid and citric acid are both used for passivation, but you already have pitting.

Larrin wrote: ↑

Mon Apr 15, 2024 8:26 pm

Nitric acid and citric acid are both used for passivation, but you already have pitting.

Hey "Larrin" are there any "passivation" methods that can be implemented by a lay person? Because I feel that corrosion is enemy of every good blade.

Also over the years I've had good results using "Tuf Cloth" by Sentry Solutions for corrosion prevention. Do you have an opinion on that particular product?

JD Spydo wrote: ↑

Tue Apr 23, 2024 7:18 am

Also over the years I've had good results using "Tuf Cloth" by Sentry Solutions for corrosion prevention. Do you have an opinion on that particular product?

I don't know anything about it