In a previous post, we talked about some broad groups of stainless steels, how they’re named and how they’re different. Here, we’re going to explore the most commonly used series of stainless steel and the two most common types stainless steel in the world.
The 300 Series
The high levels of chromium and nickel in 300 series stainless steel make the metals resistant to rust. Coupled with natural weldability, formability and strength, the 300 series is the most widely used family of stainless steel in the world. Sanitary industries like foodservice and medicine heavily prefer and, sometimes, legally demand that equipment is made of Type 304 or Type 316 stainless steel exclusively. Let’s put these two metals under a molecular microscope.
304 stainless steel, sometimes referred to as A2 Stainless Steel, is the most commonly used stainless steel in the world. It’s used for everything from screws and car and machinery parts to foodservice equipment. The typical 300 series stainless steel, it’s characterized by strength, weldability, formability and decent rust-resistance.
304 stainless steel can protect itself from water and oxidizing acids like sulfuric or nitric acid but cannot protect itself from Chlorides or saline environments. This metal won’t rust when exposed to humidity and most common acids but will rust in salty environments like ones near the sea or ocean or when exposed to industrial solvents.
316 stainless steel, also known as marine grade steel, is the second most commonly used stainless steel. Chemically and molecularly, this steel is nearly identical to Type 304 with one exception: Type 316 contains small amounts of an alloy called molybdenum.
Type 316 has all the same qualities as Type 304 with increased rust-resistance. Molybdenum provides the metal added rust protection against chlorides and saline environments. Conveniently solving the problems with Type 304.
Type 316 is essentially an upgraded version of Type 304 but it also comes with an upgraded price. Because of how expensive it is, it’s only used in environments that Type 304 wouldn’t survive –often in saline environments, boats and medical equipment. Type 316 stainless steel is one of few metals that are considered “Surgical Steel.”
The two most common types of stainless steel have very similar properties and fall within the same broad family of stainless steels. Picked mainly for their corrosion resistance, it really shows how dangerous rust can be!