As a top stainless steel sphere supplier, I’ve been asked what is the difference between regular and food grade stainless steel. Here, I’d like to help you make it clear.
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Simple definition about stainless steel
“Stainless steel” covers an entire family of alloys mostly defined as “iron alloys with more than 12% chromium so they’re relatively resistant to corrosion.” That range from high strength alloys like 13–8Mo and 440C that only pay lip service to corrosion resistance, to common, mid-grade alloys like “18/10” you see in cookware and kitchen sinks. (You may want to know full knowledge about stainless steel)
Why stainless steel called stainless
Plain steel forms an oxide – rust – that is porous, flaky, and open to exposing more metal to further attack by oxygen. Stainless steels get their corrosion resistance from chromium (for the most part), which quickly forms an oxide barrier that protects the metal from further corrosion. It’s like a built-in layer of paint that heals itself. Scratch stainless steel and you expose more chromium to oxygen.
Some stainless steel grades are highly stain resistant, but not entirely stainless. If the chromium content is not enough, a uniform Cr2O3 coating is not formed on the steel surface and the steel is susceptible to localised corrosion (pitting corrosion) under some circumstances. (You may want to know whether stainless steel is really anti rust)
Why not all stainless steel can be called food grade stainless steel
Common acids and alkaline substances in food can attack cheap stainless steels, the ones with low chromium, nickel, and molybdenum contents. Further, many cleaning chemicals contain chlorine compounds (bleach, acid) that are happy to attack the oxide layer of cheap stainless steels.
What is food-grade stainless steel
Hence food-grade stainless steels are higher-end stainless steels that can handle heavier corrosive agents found in food and kitchen cleaning chemicals. Maybe not AL6XN, but variations of the 300 series with that extra attention to resistance to pitting attack and chlorides.
Is food-grade stainless steel related to stainless steel 304#
304 stainless steel is a very common stainless steel. Its corrosion resistance is better than 430 stainless iron, boasting its corrosion resistance and high temperature resistance, and good processing performance. Therefore, it is widely used in industry and furniture decoration industry and food and medical industry, such as stainless steel decoration balls, some high-end stainless steel tableware, bathroom and kitchen utensils.
304 is a versatile stainless steel, which is widely used to make equipment and parts that require good overall performance (corrosion resistance and formability).
In order to maintain the inherent corrosion resistance of stainless steel, steel must contain more than 17% chromium and more than 8% nickel.
Generally, stainless steel 304# is not food grade, but if it is processed specially, it can be food grade.
Stainless steel 304 and 316 are used for stainless steel products that are related to “edible” or “food”. 316 stainless steel has a high price and is mostly used in high-end equipment, such as aerospace, food machinery and other fields. Food grade stainless steel used in daily necessities is mostly 304 stainless steel, which has good acid and alkali resistance and strong corrosion resistance.
Is stainless steel 201# also related to food-grade stainless steel?
No.
In comparison, 201 and 202 stainless steel (commonly known as high manganese steel) are generally used for industrial products and cannot be used for tableware because they:
● Nickel content is not up to standard, poor acid and alkali resistance, and easy to rust;
● Excessive manganese content, excessive intake of manganese in the human body will cause damage to the nervous system.
201 stainless steel contains less nickel and chromium which shows weak corrosion resistance, and contains more manganese which boasts good acid and alkali resistance, all of which makes it cheap. (You may want to know How to identify stainless steel grade 201 304 and 316 or you may want to recognize it based on its chemical Composition)