Stainless steel 304 vs 316: what are the differences between the two?

Stainless steel 304 and 316 contain high nickel and chromium content, which makes them very resistant to corrosion.

Stainless steel is used in the manufacture of a wide variety of products essential to our daily lives. From knives to household appliances to industrial components.

In this post, we are going to focus on two variants of stainless steel, 304 and 316, and how their particular characteristics influence their performance, thus helping you to make informed decisions to choose the technological solution that best suits your needs or those of your project.

WHAT IS STAINLESS STEEL?

Knives, electrical appliances, trays, shelves, surfaces for boats, structures, sheets... there are a multitude of products that are made of stainless steel.

What is stainless steel and what does it mean that an article is made of this material?

Stainless steel is basically an alloy of steel and chromium. Sometimes this fusion can also incorporate nickel, molybdenum and wolfram to improve certain properties such as corrosion resistance, tenacity, structural stability, hardness or thermal stability.

But what really makes a steel stainless is the addition of chromium, which is a hard transition metal, brittle and highly resistant to corrosion in aggressive environments. This metal has a high affinity for oxygen, and when it comes into contact with oxygen it forms an invisible passivating layer, which prevents corrosion of the iron.

WHY DOES A STAINLESS STEEL ITEM RUST?

Stainless steel has proven to be an indispensable material due to its resistance to corrosion and wear and tear, yet you are sure to have an item that is stainless steel but over time has corroded or rusted. Even so, surely you have some item that is made of stainless steel but over time it has corroded or rusted. Why has this happened if it is supposed to be resistant to rust?

Here the explanation. When an item is said to be stainless or stainless steel, what is meant is that it is made of a steel containing between 10% and 12% chromium. Chromium when exposed to oxygen forms an invisible thin layer of oxide that prevents corrosion. But if this thin layer is damaged or broken, then the protection disappears, and oxygen can reach the underlying steel, leading to rust and corrosion of the material.

How can this oxide layer deteriorate? This protective layer can be damaged by contact with water, moisture, salt, abrasive or chemical substances. So, for example, if you live in a maritime area, your household appliances can corrode or rust if they are in an environment where humidity and salt predominate.

Now, there are stainless steels that are more resistant to these exposures, such as stainless steels 304 and 316.

CLASSIFICATION OF TYPES OF STAINLESS STEELS

Stainless steels can be classified in four groups according to the metals they are made of and the quantity of each one of them: martensitic, ferritic, austenitic and duplex.

The austenitic stainless steels have austenite as their primary crystalline structure. This austenite crystal structure is achieved through additions of nickel, manganese and nitrogen, which serve as austenite stabilisers.

Within the family of austenitic stainless steels, two series can be distinguished: the 200 series and the 300 series. The main difference between the two series is that the 300 series contains a higher concentration of nickel than the 200 series.

So we already have something clear. Stainless steel 304 and stainless steel 316 have a high nickel and chromium content, which makes them very resistant to corrosion.

STAINLESS STEEL 304 versus STAINLESS STEEL 316

INOX 304 is an optimal solution for standard applications where corrosion resistance is important but not critical. On the other hand, 316 stainless steel is used when higher corrosion resistance is required, especially when the items or products are to be used or installed in aggressive environments, marine environments, or environments subject to extreme temperatures, both hot and cold.

The key is to carefully assess the operating conditions, environmental exposure, and the specific requirements of each project.

At EOS Ibérica we have interactive terminals designed and manufactured in stainless steel 304 and 316, providing the necessary flexibility to adapt them to a wide range of industrial sectors and specialised applications.

Contact now with our sales department team, they will advise you personally according to the particularities of your project or sector. The choice between 304 and 316 stainless steel is ultimately the key to ensuring optimum performance and durability in your specific applications.