Not all stainless steels are created equal. There are several grades, with varying levels of durability and resistance to heat and corrosion. Each type is made from a mixture of metal alloys that typically includes at least 10.5% chromium and more than 50% iron. Stainless steel is classified according to its composition, with four types of classification:
Austenitic, which contains high levels of nickel, chromium and molybdenum to provide optimum strength and ductility. It is the most common type of stainless steel used for cooking.
ferritic, which contains more than 10.5% but less than 30% chromium. (These options are usually magnetic, which may lead some buyers to think the cookware isn’t actually stainless steel, but in fact, they’re best if your priority is to prevent corrosion cracking underneath. stress and high temperature oxidation.)
Duplex, which is a combination of austenitic and ferritic stainless steel. This option offers the best of both worlds in terms of durability and corrosion resistance, but is better suited for industrial and underwater use than for culinary purposes.
martensitic, which is similar in composition to ferritic, except that it has increased levels of carbon. This is typically used for medical and surgical grade instruments.
Grade 304 is the most common food grade austenitic stainless steel, meaning it meets all the criteria necessary for use in food preparation, storage and consumption. (You may also see it on the packaging as 18/8 and 18/10.) Unlike 316-grade stainless steel (more on that below), it does not contain molybdenum, which means that it does not hold up as well over time. prolonged and repeated exposure to certain ingredients such as salt or acidic foods such as lemon or tomato juice.
Grade 316 is another excellent food grade stainless steel, but it is expensive. The added molybdenum helps prevent corrosion and pitting while providing greater heat tolerance (hence the price premium).