Why don't they just used uncoated blades?

[rbscebu]

Do you mean this in the sense that the manufacturer actually applies some form of chromium oxide to the blade? My understanding was that the chromium in stainless steel oxidizes itself to form a "stainless" surface layer (or acid is used to bring this out and eliminate iron that would rust on the surface).

Your understanding is correct. I did not state that the manufacturer applied a coating of CrOx to the stainless steel, just that the stainless steel has a coating of CrOx on it.

 

[ShavingPrimate]

My understanding was that the chromium in stainless steel oxidizes itself to form a "stainless" surface layer (or acid is used to bring this out and eliminate iron that would rust on the surface).

The explanation I have heard, is that chromium, while essential to make stainless steel stainless, also has the property of making it hard.

As a certain content is necessary, by adding a thin layer of chromium to the surface of the blade will give it added protection without increasing the hardness of the blade itself.

This better protects the blade, while allowing it the flexibility it needs to bend without breaking.

In an unflexable metal, such as a knife. The chromium in the metal forms on the surface, where it reacts with oxygen and forms a protective layer that protects the metal underneath.

 

[FloppyJoe]

What recall is that the type of stainless used is not very homogenous. Think of carbon steel as very fine sand where are all the particles are uniform in size. When you build a pyramid in that sand it is very easy to make it uniform.

Now throw some random shaped rocks into the sand to represent the carbides that make stainless stainless and try to build that same pyramid. Not very uniform with gaps, peaks etc…. The sharpening effectively rips out some of the rocks as well.

The coating is intended to smooth out the jagged edges.

That is what I recall as an explanation. Seems reasonable but I am not schooled metallurgy.

 

[BigJ]

I don’t think the coating on the blades wears completely ‘off’. I think it wears ‘down’ and still creates a buffer into places in the steel that are irregular. My theory is that it is that excess coating that we dislike on initial shaves but the coating that sticks past that does help.

+1! This is also my understanding.

However, I am neither an engineer nor a materials scientist so what do I know?