Judging by the name, you might assume that stainless steel never stains—but you’d be wrong.

Stainless steel stains less easily than other iron-based metals, but it’s not literally “stainless”. Just like standard steel, stainless can get marked up by fingerprints and grease, discolor, and eventually rust. The difference is resilience. Stainless steel can withstand much more time and abuse before showing signs of wear.

WHAT IS STAINLESS STEEL?

All steels have the same basic iron and carbon composition, but stainless steel also contains a healthy dose of chromium—the alloy that gives stainless steel its famous corrosion resistance.

There are multiple grades, each with slightly different alloy composition, and therefore slightly different physical characteristics.

Stainless steel must contain at least 10.5 percent chromium. Depending on the grade, it may contain much higher chromium levels, and additional alloying ingredients like molybdenum, nickel, titanium, aluminum, copper, nitrogen, phosphorous or selenium.

304 STAINLESS STEEL

304 stainless steel is the most common form of stainless steel used around the world, due to its excellent corrosion resistance and value. It contains between 16 and 24 percent chromium and up to 35 percent nickel, as well as small amounts of carbon and manganese.

The most common form of  304 stainless steel (18/8) stainless steel, which contains 18 percent chromium and 8 percent nickel.

304 can withstand corrosion from most oxidizing acids. That durability makes 304 easy to sanitize, and therefore ideal for kitchen and food applications. It is also common in buildings, décor, and site furnishings.

304 stainless steel does have one weakness: it is susceptible to corrosion from chloride solutions, or from saline environments like the coast. Chloride ions can create localized areas of corrosion, called “pitting,” which can spread beneath protective chromium barriers to compromise internal structures. Solutions with as little as 25 ppm of sodium chloride can begin to have a corrosive effect.

COMMON USES FOR 304 STAINLESS STEEL:

• Storage tanks
• Fasteners and finishing hardware (screws, nuts, bolts, plates, handles)
• Pots and pans
• Residential sinks and sink parts
• Indoor architectural/decorative hardware (panels, sculptures, sconces)
• Equipment tubing
• Residential appliances

316 STAINLESS STEEL

316 grade is the second-most common form of stainless steel. It has almost the same physical and mechanical properties as 304 stainless steel, and contains a similar material make-up. The key difference is that 316 stainless steel incorporates about 2 to 3 percent molybdenum. The addition increases corrosion resistance, particularly against chlorides and other industrial solvents.

Alternative 300-series grades can contain up to 7 percent molybdenum. They provide even better chloride resistance, but such heavy-duty resistance is only necessary in industrial or high concentration exposure conditions.

COMMON USES FOR 316 STAINLESS STEEL:

• Industrial equipment as used in:
  • Pharmaceutical manufacturing
  • Chemical manufacturing
• Industrial and chemical transportation
• Pressure vessels
• Cisterns and pipes for chemical applications
• Medical equipment where non-surgical steel
• Marine equipment
• Outdoor site furnishings
• Commercial kitchens
• Food production and processing in saline environments
• Commercial appliances

Both 304 and 316 stainless steels (as well as other 300-series grades) use nickel to maintain an austenitic composition at lower temperatures. Austenitic steels ensure a versatile balance of strength, workability, and corrosion resistance, making them ideal for outdoor architectural features, surgical instrumentation, and food processing equipment.