Category: Corrosion Resistance
2 thoughts on “Corrosion Resistance”
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Corrosion Resistance Testing of Stainless Knife Steels
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Corrosion Resistance of Steel
How to Design Knives that Do Not Fail
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Failure Modes
A common engineering technique is to evaluate designs based on how they failed, or may fail. Failure modes are identified and the designs are modified to prevent those failures. These ideas are simple in concept but it is surprising how easy it can be to miss the forest for the trees. In terms of predicting failure modes in some cases it is easy and in some it is difficult. You would expect a large chopping knife to require heavier edge geometry to prevent chipping and rolling, or a seawater diving knife to require high rust resistance. Other times failure modes are identified through testing of the knife or by returns from customers. Whatever the source of the failure, there are usually relatively simple methods for fixing each one, though the trade-offs for doing so may not be desirable.
H1 Steel – How it Works
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Austenitic Stainless Steels
At its most basic, H1 is an austenitic stainless steel. Austenitic stainless steels are about as old as stainless steel itself, being developed by German metallurgists in the approximate time period of 1909-1912. They worked on 18% Cr, 8% Ni steels which are quite similar to common austenitic stainless steels like 301, 302, and 304.
Does Acidic Food Affect Edge Retention?
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I was interviewed on the Knife Junkie Podcast, so make sure you check that out.
Acidic Food
Carbon steel knives are frequently used in kitchens, probably the majority of them made by Japanese bladesmiths and knife companies. Kitchen knives cut a variety of foods, and some of them are corrosive. There has been some debate about whether any of these potentially-corrosive foods can actually affect sharpness or edge retention of kitchen knives. Sharpness is controlled by the radius/width of the edge. You can read more in the article on sharpness vs cutting ability.
Which Knife Steels Have the Best Corrosion Resistance?
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Update 1/6/2020: I have since performed my own corrosion resistance testing and provided updated analysis.
Nitrogen-Alloyed Knife Steels
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In previous posts I have written about the process by which steel is hardened. The steel is heated to a high temperature phase called austenite, where carbides are dissolved and carbon goes into solution in the austenite. During rapid quenching the carbon is trapped between the iron atoms and a phase called martensite is formed. Martensite gains its high hardness from the distortions to the atomic structure that come from carbon in between the atoms.
Carbon vs Stainless Steel in Knives
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Steel History – The First Stainless Steel was for Knives
Update 7/23/2018: I added a small piece of new information on the development of 440C steel to the article.
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The writing of this article was made much easier due to the existence of The History of Stainless Steel by Harold Cobb [1]. If you want more information on the history of stainless and the people who developed it, check out the book.
How Much More Chromium Does D2 Need to be Stainless?
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Some materials like aluminum form a passive oxide layer that prevents further corrosion. Steel is not one of those materials. Instead, steel forms iron oxide, or rust, that doesn’t protect the underlying iron and flakes off leading to further corrosion. However, when sufficient chromium is added then a chromium oxide passive layer forms which protects the steel from corrosion in a similar way to a metal like aluminum with its own aluminum oxide layer. A simple schematic diagram shows the passive film vs rust [1]:
This was really informative article, As corrosion is a big problem for steel and other metal but resistance can control this problem. Thank you for sharing this.
Larrin,
Has anyone ever attempted to mostly use Molybdenum, or Moly/Nitrogen, as the leading corrosion resistant element in a steel to eliminate or mitigate chromium in a steel? I need to double check the corrosion resistance formula you created, but I was curious if it is possible for an all Moly “440”.
Maybe a Niobium/Moly homunculus is possible.