When selecting stainless steel hardware, it is important to understand the differences between the variety of grades and finishes available so you can choose the products that will work most safely and effectively for your purposes.
It’s difficult to distinguish between these two types of steel visually, but significant differences between the two steel types do exist and are important to understand. Below is a basic guide to the similarities and differences of 304 grade and 316 grade stainless steel.
1. Composition The first key difference between 304 grade stainless steel and 316 grade stainless steel relates to composition. Steels are classified in part based on chromium and alloy content and crystalline structure. Austenitic steel – also known as 300 series steel – contains 18% chromium and 8% nickel. This type of steel is incredibly common; about 70% of stainless steel products are composed of austenitic steel. 304 grade stainless steel is considered to be austenitic, while 316 grade stainless steel is considered to be superaustenitic – meaning it contains a higher content of molybdenum, nitrogen and nickel, making it more resistant to corrosion and stress.
2. Resistance to Corrosion While both 304 and 316 grade stainless steels are resistant to corrosion, 316 grade stainless steel provides a higher degree of corrosion resistance than 304 grade steel because it includes molybdenum in its composition. As a result, 316 grade stainless steel is better suited for resisting extreme environmental conditions like salt water, de-icing salts, brine solutions and exposure to chemicals. Though 304 grade stainless steel will resist corrosion for a time, it will eventually begin to tarnish.
3. Cost Typically, 316 grade stainless steel costs slightly more than 304 grade steel because of its enhanced chemical and production properties. The extra cost can be justified, however, because hardware made of type 316 stainless steel is extra resistant to tarnish and corrosion, enabling it to last a very long time.