Chemical difference between steel & stainless steel?

Question

What is the difference between regular steel & stainless steel? Why does steel rust but stainless wont? Is stainless some kind of alloy or something? Any knowledgeable input would be great. Thanx!

Answer 1

In metallurgy, stainless steel is defined as a steel alloy with a minimum of 11.5% chromium content by mass. Stainless steel does not stain, corrode or rust as easily as ordinary steel (it "stains less"), but it is not stain-proof. It is also called corrosion resistant steel when the alloy type and grade are not detailed, particularly in the aviation industry. There are different grades and surface finishes of stainless steel to suit the environment to which the material will be subjected in its lifetime. Common uses of stainless steel are cutlery and watch straps.



Stainless steel differs from carbon steel by amount of chromium present. Carbon steel rusts when exposed to air and moisture. This iron oxide film is active and accelerates corrosion by forming more iron oxide. Stainless steels have sufficient amount of chromium present so that a passive film of chromium oxide forms which prevents further corrosion

Answer 2

There are many things in life that I wonder about. Being in the steel industry and selling stainless steel I have at one point in my life asked myself, why do they call it stainless steel? What makes it stainless? It doesn't take much to find out but here is a very brief synopsis of what makes stainless steel stainless so that you can check one more thing off the list in your quest for knowledge.



Stainless Steel might or might not have been invented by a man named Harry Brearley in 1912. Steel has been around for hundreds of years but it hasn't always been stainless. Only after the exact combination of elements had been achieved did we start calling a certain type of steel "stainless". His magic potion contained the keys to what is now called "stainless steel". That being said, the true inventor of stainless is still an ambiguous cloud at best. However, this isn't a discussion on WHO invented stainless but what stainless is and how it's actually stainless. Here is a great article posted by British Stainless Steel Association in regards to the history of stainless as a whole, see here.



So what is in this magic potion that makes a steel not stain or rust? As most of us know if you leave regular steel or metal out in the elements it will rust, oxidize, or stain. Why does stainless not stain? When Harry Brearley Brearley created a steel with 12.8% chromium and 0.24% carbon, that was believed to be the first ever stainless steel. Chromium is the element in stainless that improves the corrosion resistance by forming a chromium oxide film on the steel. This very thin layer, is what allows the steel to be impermeable to rust or staining and when placed under the right conditions, it can also be self-repairing to a certain extent.



There you have it. The answer is Chromium. Chromium is the element when mixed w/other elements in the proper amounts to form the thin layer that protects the steel from rusting, staining or corroding. Hope that helps you in your pursuit of knowledge.

Answer 3

steel is also an alloy - principally of iron and carbon. The reason ordinary steels rust is that the iron oxide is not tightly bound to the surface, revealing fresh metal to be oxidised. Stainless (like aluminium and titanium, both very reactive metals) forms a tough coat of oxide that protects the bulk.

Answer 4

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