Magnacut rust from pocket carry

[Matus]

I am jut wondering - up to what extend can a HT be optimized for rust resistance while delivering also the desired edge holding/stability/toughness properties?

[SaltyCaribbeanDfly]

I am jut wondering - up to what extend can a HT be optimized for rust resistance while delivering also the desired edge holding/stability/toughness properties?

Maybe Larrin will chime in on that as he’s the expert but I can tell you from my experience so far with the Native Salt Magnacut it hasn’t shown any signs of rust and I carry it in my WB just like all my H1/2 and LC200n knives…there’s usually a definitive dried up salt line on the blade at the end of the day and I just rinse it off…when it’s time to do a little cleaning I drop it in a plastic bowl with warm water and Dawn, then scrub away with a toothbrush…easy peasy

[Larrin]

In general optimizing for corrosion resistance is not at odds with optimizing for other properties. The main parameters that control corrosion resistance are austenitizing temperature and tempering temperature. Higher austenitizing temperature means higher hardness and higher corrosion resistance. There is a maximum temperature before hardness drops, that temperature is higher and hardness greater when using cryo.

When it comes to tempering there is a relatively wide range where corrosion resistance is largely unaffected. However, there is a relatively common practice of tempering in the “high” or “secondary hardening” range which is around 900-1100F. While typically a higher tempering temperature means lower hardness, in high alloy steels, especially those with molybdenum, the hardness goes up again in that range. This practice is common because it makes steel less sensitive to overheating, such as grinding/sharpening or using certain coatings. The hardness increases in that range because new tiny chromium and molybdenum carbides are precipitated. When those carbides are precipitated in steels those alloying elements are unable to contribute to corrosion resistance. My own tests showed that tempering in the high range leads to steels like LC200N and Vanax behaving like other stainless steels when it comes to corrosion resistance.

However, as mentioned there are other factors aside from heat treatment. Surface finish is important, the higher the polish the greater the corrosion resistance. Remaining steel particles from grinding are a common issue. And Spyderco has talked about finding compatible materials in their folders to avoid galvanic corrosion.

[Matus]

Thank you Larrin for a detailed explanation.

[Bemo]

What a treasure Dr. Thomas is!

[N. Brian Huegel]

Larrin, would passivation or electropolishing be helpful in preventing corrosion on MagnaCut? Particularly as bead blasted finishes expose more surface area than stonewash, satin or mirror polishing?

nb

[Larrin]

Passivation is treating with acid to remove iron particles and to force the chromium oxide to form at the surface. The oxide forms on its own but passivation helps. It could be helpful but it doesn’t seem to be standard practice in the knife industry.

[dj moonbat]

My first thought is that it looks like the bug is missing from the blade... I'm in the woods with Magnacut now and so far I can say my Spyderco is earning it's Salt name. I've been carrying it since January in the wet and snow. No maintenance beyond wiping the blade with a wet paper towel or a quick scrub, in the sink, with an old toothbrush and dawn dish soap. I sing the praises and wish you the best of luck with yours.

I did not know Sunny D had branched out into booze. Good marketing decision.

[SaltyCaribbeanDfly]

What a treasure Dr. Thomas is!

Agreed!!!

[SaltyCaribbeanDfly]

Lather…Rince…Repeat

[Bill1170]

Brad-blasted finishes seem ideal for holding paint, but inferior to almost all other finishes for resisting corrosion. Even a satin finish can be made more resistant by polishing. I did this on my two Spyderco knives with ZDP-189 blades and it helped a lot.