Selecting Stainless Steel for Your Sterile Cleanroom

Before we delve into what stainless steel to use in your cleanroom and why, we want to give some basics about what stainless steel is which will help you better understand why the grade of stainless steel matters when choosing cleanroom equipment.

Steel is iron combined with carbon. It is stronger and has better tensile strength than iron. To turn steel into stainless steel, you must add at least 10% chromium. This makes the steel more resistant to corrosion. The chromium results in a thin layer of chromium oxide that protects the steel from rust, corrosion, and other effects of exposure to air better than raw steel. Through a natural occurrence, oxygen in the air combines with the chromium to form this chromium oxide film that passively protects it. Note that contamination of the surface with dirt, oils, or other materials reduce the protection and can and trap corrosive solutions making it less corrosion resistant. Because of this, frequent cleaning can improve corrosion resistance.

Stainless steel is most often a complex alloy of not only iron, carbon, and chromium, but also, small quantities of nickel, molybdenum, and other elements. In fact, there are more than 100 grades of stainless steel.

These stainless steel materials are categorized based on composition and internal structure into 5 general types:

• • excellent form-ability
  • notable cryogenic properties
  • good hygiene factor
  • the most common type of stainless steel produced is 304 for kitchen and food processing use
  • typical applications: medical implements, razor blade components, jet engine components, power generation,
  • learn more about austenitic stainless steel

• ferritic
  • contain 12-18% chromium without nickel, low carbon
  • ferro-magnetic
  • good corrosion resistance
  • fair weld-ability
  • not harden-able by heat treatment
  • less ductile than austenitic steels
  • typical applications: kitchenware, industrial equipment, automotive fasteners, heater and furnace parts
  • learn more about ferritic stainless steel
• duplex
  • contain 18-28% chromium and 4-8% nickel which gives a mix of austenitic and ferritic structure (hence “duplex”)
  • generally twice as hard as austenitic or ferritic
  • stronger and more ductile
  • superior corrosion resistance even in oxidizing and acidic solutions
  • good pitting resistance
  • good weld-ability
  • typical applications: pressurized process plant equipment, oil and gas piping, cargo tanks, food processing equipment
• martensitic
  • contain 11-14% Chromium without nickel with a slightly higher carbon content compared to the austenitic and ferritic
  • ferro-magnetic
  • harden-able by heat treatment
  • high strength
  • moderate corrosion resistance
  • poor weld-ability, tempering improves
  • lower carbon versions are less form-able
  • typical applications: cutlery, surgical instruments, bearings
  • learn more about martensitic stainless steel
• precipitation hardened
  • similar to other stainless steel and nickel-based alloys except they contain small amounts of copper, aluminum, phosphorus, or titanium.
  • stainless steel manufactured to address tradeoffs between the properties needed for manufacturing and end use. When cost or performance challenge an application, precipitation hardening stainless steel (PH) can offer solutions
  • Typical applications: strip and wire components that must be extensively formed or drawn during manufacturing, that then must have high strength and toughness.
  • learn more about precipitation hardened stainless steels

• 316 is austenitic steel containing molybdenum to increase resistance to various types of deterioration and corrosion.
• 410 is the most commonly used martensitic stainless steel because of it is economical, high strength, and heat-treatable, but only for applications that are not highly corrosive.
• 430 is the most widely used ferritic stainless steel, offering standard corrosion resistance. It is often used in decorative applications.

• 316 – (16% chromium, 10% nickel, and 2% molybdenum) the second most common stainless steel produced. It is popular in cleanrooms because the molybdenum increases corrosion resistance and strengthens it against pitting that can be caused by solutions such as solvents and cleaners. It is superior to 304 in its resistance to chloride corrosion and harsh chemicals. Referred to as A4 by ISO.

Stainless steel cleanroom furniture and fixtures in sterile areas must be disinfected frequently so corrosion and pitting resistance against harsh cleanroom disinfectants and sterilants is vital. So most sterile cleanroom furniture such as work benches are 316 grade stainless steel. As a material, it is more expensive than the other grades, but necessary as it can withstand harsh cleaning chemicals and chemical spills.

Type 316 stainless steel is the most used grade in the pharmaceutical and medical industries.

At Cleanroom Connection, we can help you select the right stainless steel furniture and equipment with confidence that it will withstand your cleaning procedures and hazardous drug spills. We offer stainless steel trolleys, stainless steel tables, and other furniture such as our custom cleanroom chairs. Try our cleanroom chair design tool to select the features you want then simply order.