There is no single answer to the question “what is the best stainless steel?” in the food service and food industry sectors. Making candy is not the same as making cheese: the temperatures used and, more importantly, the chemical composition of the processed foods change. In the canning industry, the most widely used alloys are AISI 316 and AISI 430.
AISI 316 Stainless Steel
316 is an austenitic stainless steel with a high chromium and nickel content. Like almost all metals, it has a use temperature range far beyond what is required for food preparation. This steel is particularly suitable for food contact because it has high resistance to acids, bases, and chlorides, such as salt. Other austenitic stainless steels (such as aisr) can develop strong pitting. 316 is immune to this type of corrosion and is therefore suitable for almost all applications.
AISI 430 Stainless Steel
Metallurgically, AISI 430 stainless steel is very similar to 316. It has the same chromium content but a much lower nickel content, making it less expensive. Another important difference is that AISI 430 is a ferritic alloy, meaning it is magnetic. Ferritic alloys have very high resistance to stress corrosion cracking, which is the formation of cracks under mechanical stress in corrosive environments. Stainless steel 430 also has very good resistance to organic acids and nitric acid and is therefore used in contact with acidic foods. Resistance to oxidation and sulfur-containing substances is also excellent.
On the other hand, because of the low nickel content, this alloy is not very resistant to reducing acids contained in some foods.
So?
In general, AISI 316 is the best choice for machinery and containers for the canning and food service industry. Its ability to resist salt and acidic foods such as tomatoes and citrus makes it an excellent material. For less critical applications, AISI 430 may be a cheaper but equally good compromise. Regardless of the alloy used, it is important to use a low roughness finish, such as that obtained by polishing or electropolishing. Removing micro-roughness reduces the risk of cracking and corrosion, and facilitates cleaning.
Freely excerpted and translated from https://www.gasparini.com/