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Author Topic: Why does stainless steel sometimes go rusty?  (Read 1561 times)

Offline chris

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Why does stainless steel sometimes go rusty?
« on: 02/02/2014 22:53:32 »
I was asked the other day by a distressed housewife why her new "stainless" steel cutlery was going rusty?
« Last Edit: 07/02/2014 09:10:34 by chris »


 

Offline RD

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Offline CliffordK

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Re: Why does stainless steel sometimes go rusty?
« Reply #2 on: 03/02/2014 08:49:05 »
Apparently it is a bit more complicated than that.
Stainless steels come in various grades.

Martensitic grades of stainless steel are those that can be hardened which is vital for making good knife blades.  However, they all have low nickel content.

Austenitic grades of stainless steel have higher nickel content and excellent corrosion resistance, but can't be hardened, and thus make poor knife blades. 

You will note that the knife blades are all strongly attracted to magnets, whereas high quality marine grade stainless steels are not.

The notes I'm seeing indicate that Molybdenum gives high corrosion resistance to the Martensitic stainless alloys. 

There is also a group of precipitation hardened stainless steels which require maintaining the metal at an elevated temperature for an extended period during the hardening process.  I presume this process also increases the manufacturing cost.
 

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Re: Why does stainless steel sometimes go rusty?
« Reply #2 on: 03/02/2014 08:49:05 »

 

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