Molybdenum and its effect on pitting

shao.fu.tzer

shao.fu.tzer

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While doing some research on what knife I should buy for my bathroom (I keep a knife hidden in every room of the house) I came across some interesting information on corrosion - pitting in particular. There seems to be a formula for calculating the pitting resistance of stainless steel. I'd never heard of such a thing so I thought I'd share with my fellow forumites.

PRE: Pitting Resistance Equivalent

PRE = %Cr + 3.3 x %Mo + 16 x %N

According to this equation, Molybdenum is a major player in pitting prevention. Up until I read this I thought it only increased toughness or ductility. The source seems reputable:

http://www.azom.com/details.asp?articleID=1177

Anyway, it should probably be added to the Steel FAQ if its true. What do you guys think?

Shao
 
That's why for harsh environments 304 stainless is replaced with 316. The 2% Mo addition in 316 makes a big difference.
 
Cliff Stamp said:
Yes it is one of the many ways in which molybdenum effects steels.

-Cliff
Click to expand...

Cliff -

What does the Cobalt in VG-10 do? Spyderco seems to be the only one to use it. Do you know why? ATS-55 also has Cobalt. Does it result in higher temps when heat treating or higher RC values?
 
From Spyderco.com

"Cobalt (CO)
• Increases strength and hardness, and permits quenching in higher temperatures.
• Intensifies the individual effects of other elements in more complex steels."
 
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