MAGNETIC STAINLESS STEEL?
Info or intox: should stainless steel magnetize? If it is common to hear that the magnet test can determine the quality of stainless steel, it turns out that this statement is not necessarily true. It is a misconception to think that the magnetized stainless steel is a pledge of poor quality, in fact it is quite the opposite…. Stainless steel includes several variations, which can be classified into different categories: martensitic stainless steel and austenitic stainless steel. One is magnetic and the other is not, yet both are quality stainless steel.
Austenitic stainless steel (not magnetic)
So-called austenitic stainless steels are non-magnetic or very little. They are often used in the field of design and furniture. They are sold much more expensive (understand here with much more margin) than their ferritic or martensitic (magnetic) equivalents which are however used in nuclear and oil platforms, hence the confusion. Austenitic stainless steel is the only stainless steel to be non-magnetic.
This characteristic is explained by nickel or manganese which modifies the stacking of chromium and iron atoms, and therefore removes its magnetic character, unlike ferritic stainless steel. These two types of stainless steel adapt to food contact, are hygienic and resist corrosion, shock and high temperature.
Ferritic or martensitic (magnetic) stainless steel
Ferritic or martensitic stainless steels are magnetic. Contrary to popular belief, there is no correlation between magnetism and corrosion resistance. Whether it is austenitic, ferritic or martensitic, stainless steel is a stainless and therefore resists corrosion, thanks to the chromium present in its composition. The magnet test therefore does not determine the quality and resistance of the stainless steel to corrosion. As a reminder, 316 or 316L stainless steel (for low carbon, lightened carbon version designed for TIG or MIG welding), is composed of more than 65% magnetic iron, 12% magnetic nickel and only 18% of non-magnetic chrome.
Ferritic and martensitic stainless steels are therefore not poor quality stainless steels, quite the contrary. They protect continuously and have better price stability, unlike austenitic stainless steel. In addition, they are harder and stiffer and are therefore more resistant.
The magnet test is therefore not significant and therefore does not alone make it possible to determine whether or not the stainless steel will be resistant to corrosion.