Visually, there is no difference at all, 304 grade steel and 316 grade steel are polished, grained and finished in the exact same way. The only way to determine the difference is to request a material test report (MTR).
It’s in the material ‘make-up’ that the differences can be found and although the differences are very slight, they do alter the purpose for which each type of steel can be used.
In the simplest way I can muster, the difference between 304 grade stainless steel and 316 grade stainless steel is as follows:
· 304 – contains 18% chromium and 8% nickel
· 316 – contains 16% chromium, 10% nickel and 2% molybdenum
What Do These Differences Mean?
With the addition of molybdenum to 316 grade stainless steel, the resistance to corrosion is enhanced, particularly against chlorides [such as sea water and de-icing salts]. It is this enhanced corrosion protection that makes 316 different from 304 stainless steel. Top 10 Product
The case for 304 grade stainless steel
304 grade stainless steel is considered the most versatile and widely used of the austenitic stainless steels. The 304 steel type is capable of meeting a wide variety of physical requirements making it an ideal material to use for applications such as wheel covers, kitchen equipment and storage tanks.
304 steel provides good resistance against moderate acidic attack, but is considered inferior when compared to the 316 steel type.
The case for 316 grade stainless steel
When compared with 304, 316 is considered to be more heat-resistant and provides superior corrosion resistance, due to the presence of the molybdenum element.
316 is considered to be far more resistant to a number of chemical solutions such as sulphuric acid, bromides and iodides. Its ability to withstand such solutions make it the preferred material of use for applications to be installed in pharmaceutical facilities or medical environments.
In some pharmaceutical facilities grade 316 applications are required, by law, to be installed in order to prevent excessive metallic contamination.
So, Which Is Best?
The answer to this question is subjective, both steel types have their uses, it’s a matter of opinion. For instance, commentators within the security industry would argue the case for type 304 steel. A proportion of ‘experts’ across the security industry dispute the ‘superior’ corrosion resistant claims put forward for type 316 steel.