Reactiveness on carbon steels.

timos-

timos-

Knifemaker / Craftsman / Service Provider
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This question is focused on what kitchen knife enthusiasts call Reactivity of carbon steels. What is it exactly that cause some types of carbon steels to be more reactive than others?

Would 52100 be considered less reactive than say W2? 1084 more so than 1095?
 
I would think the Cr would contribute to reducing "reactiveness". And 52100 has 1.5% of it....it also finishes "brighter". I don't have a 52100 kitchen knife of my own to judge that by, so take that with a grain of salt, but out of the low alloy carbon steels we mostly use, from 1084 thru 52100, I would think 52100 would be less reactive than most others. O1 seems to rust if you look at it funny, and then 1095 close behind O1. 1084 and 1095 would be about identical in reacting to corrosion, same with W2. My personal list from least reactive to most would be: 52100, 15n20, 1084, W2, 1095, O1. Just my 2 pesos.
 
I have made and used a bunch of knives out of both 52100 and 1084. In my experience the 52100 is clearly less reactive than 1084. I can't speak to the other steels.

Chris
 
Sometimes I wonder If people refer to reactivity based on the type of colors that develop as a patina. It does seem that the higher carbon least stain resistant steels are considered to be the most reactive.
Would it be accurate to say that surface finish could also influence "reactivebness" based on way light can reflect off the surface? May be way overthinking at this point :)
 
It's a fascinating question; I wish I had actual answers to it. :/ I suspect the differences in reactivity among the "carbon" steels we typically use are pretty negligible.

I don't think it has much to do with light reflection, but surface finish definitely affects how quickly any steel corrodes (reacts with oxygen, high or low pH, etc.) Smoother is better for resisting corrosion.

Personally, I have given up on giving much of a hoot about corrosion-resistance or reactivity when dealing with "carbon" steels. I just choose them for the cutting/performance/edge-holding characteristics I want. I don't like coatings so if corrosion-resistance is a major factor, I simply use an alloy with a bunch of chrome in it :)

Funny story... about a year ago I gave my mother-in-law a chef's knife made of 1095. She really liked it, and still uses it every day... but a couple months later she called my wife and asked, "This knife is turning grey/black! Did I ruin it somehow? Will James be mad at me?" No ma'am, I'm not mad. Patina is perfectly normal for that kind of steel and it doesn't hurt a thing :)
 
I think is mainly a matter of alloying. Chromium, nickel, and other additives can affect the reactivity ... they react less to acids, and shield the iron somewhat.

The HT can somewhat affect the reactiveness, but that would be in a less than optimum HT. Done right, the carbon content should be tied up with the iron as martensite and cementite, it is the alloy content in the boundaries that will shield the iron/carbon structures from reacting with acids.

I may be off a bit on this, but that is how I think it out.
 
Chefs may also judge reactivity by how it reacts with food, which is to say whether or not a certain steel lays a stink on whatever food you are cutting or makes the food change color.
 
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