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Views:1     Author:Site Editor     Publish Time: 2019-05-28      Origin:Site

To answer this question, we first need to deal with two concepts:

1. What's steel?

An alloy material consisting mainly of iron and containing two or more elements is called steel. For example, when carbon is added to iron, carbon steel is obtained, and its hardness is much higher than that of pure iron. In addition, there are high-speed steel, spring steel, bearing steel and so on.

2. What's rust?

In fact, the so-called rust is a metal and oxygen reaction after the formation of an oxide. In this sense, a considerable amount of metal will rust, such as Verdigris is a kind of rust.

It is generally believed that rust is always a bad thing, but in fact, it is not. The reason why many active metals are not consumed in the air is simply that their rust forms a protective film on the surface of the metal Keeping them out of the air protects the interior material from further corrosion, as is often the case with Aluminum.

Back to rust. It is harmful because when iron or ferroalloys come into contact with air, they form on their surfaces what is commonly known as "red rust" formally known as iron(III) oxide hydrate, with the Chemical Formula Fe2O3·nH2O. This red rust is very porous so oxygen and water will continue to permeate, forming a continuous oxidation reaction, until the depletion, or iron completely oxidized just stop.

To sum up, in short terms, the so-called stainless steel is in the air or weak acid environment, will not be corroded ferroalloy.

In addition, the corrosion-resistant steel in the strong acid environment, there is another term "acid-resistant steel", in general, acid-resistant steel has stainless steel characteristics, stainless steel is not necessarily acid-resistant.

stainless steel

Now we can talk about stainless steel.

Let's start with where it came from.

The invention of stainless steel has been variously described, most famously by a British man, Harry Brearley, who stumbled across it in 1912 while researching weapons steel for his country's arms dealers. When he used a metallurgical etchant on steel containing 0.24% carbon and 12.8% chromium, he found that dilute nitric acid was of no use to the material. So he realized it was new corrosion-resistant material. Although this material is not wear-resistant and cannot be used as a weapon, it must have a wide range of uses in the food industry.

 Harry Brearley

That's the Guy Right there

He immediately began working with cutlery manufacturers to make the knife, and after extensive experimentation and refinement, he patented it at the United States Patent and Trademark Office in 1915 and published a notice in the New York Times.

An announcement, as it appeared in the 1915 New York Times, of the development of stainless steel.[5]

A 1915 New York Times announcement on the invention of stainless steel

At this point, stainless steel official debut.


A careful classification can be made by reference to the various national standards of China for stainless steel, and there are three broad classifications by composition:

No alt text provided for this image

The common 304 stainless steel in food industry belongs to 18 / 8 stainless steel, the main reason is that the lead content is very low, generally used as food containers, and stainless steel knives are mostly 13 chromium stainless steel, of which the more extensive is 440C Because of the high content of carbon and chromium, it has relatively better strength and hardness and is easy to stand out.

One more thing:

There is something on the market called "304 stainless steel", here in particular. First of all, the word "stainless steel" does not exist in the industry, it is just used to deceive consumers said. The idea is to demagnetize ordinary steel (either by disrupting the magnetic field lines or by heating the Curie Point) and deceive consumers by using the standard "it's stainless steel if it can be held by a magnet" test. Remember, there is only "304 stainless steel", there is absolutely no "304 stainless steel".


[1]what is Rust-From Wikipedia

[2]who is Harry Brearley-From Wikipedia

[3]what is stainless steel-From Wikipedia

[4]Corrosion Resistance of Stainless Steel to Sulfuric Acid-From Sciencing

[5]Picture-From"A non-rusting steel".New York Times.31 January 1915.

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Written by Janus Liu From RONSCO

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