Surgical instruments and other reusable devices must be effectively reprocessed so they are safe and functional for patient use. Before an instrument can go through sterilization or high-level disinfection, it must be cleaned. To ensure quality outcomes for the patient, the cleaning process requires consistency and standardization.
Before reviewing the details of the process, it’s important to understand the distinction between “cleaning” and “disinfection.” Here are a few key definitions to know:
WHAT IS STAINLESS STEEL?
Two main criteria to be considered when choosing the instruments are the quality of the steel and the manufacturing process itself. Manufacturing quality instruments involves standards for various aspects of the manufacturing process, including the basic requirements for quality steel, as well as vigorous inspection for every step on the process.
Stainless steel (Inox in Europe) is a mixture of metals, all playing different roles in the final alloy. Common elements found in steel composition includes:
- Pure Iron (Fe) is highly corrosive and soft, but when combined with othermetals, it becomes by far one of the most commonly used industrial materials.
- Carbon added to the iron gives it hardness, adds consistency when the metal is welded and provides ductility. Ductility defines how a solid material stretchesunder tensile stress.
- Chromium adds resistance to corrosion, and in combination with the oxygenin the air, creates a more adherent surface film that resist further oxidation.
- Nickel, magnesium, silicon, molybedum and sulfur are called residual elements and are retained from the raw material. Unless the chemical composition of steel calls for a minimum or maximum of this elements, theymay be present in the composition.The degree to which the steel become “stainless” is determined by all these metals, by the heat treatment applied and by the final rinsing process. The additives increase the metal’s capacity to resist highly corrosive environments such as blood, body fluids, salt solutions, cleaning solutions and sterilization methods.Based on the mechanical properties and composition, the American Iron and Steel Institute (AISI) differentiate all steel, about 80 types, by using 3-digits numbers. The most used types of steel, when making surgical instruments, are the 300 and 400 series described below . This types of steel is rust and corrosion resistant, has good tensile strength and will provide a sharp edge for repetitive use. The 300 series steels are manufactured from the austenic steel class and cannot be hardened by heat treatment. 400 series steels are manufactured from the martensenic steel class series and can be hardened by heat treatment.
- Stainless Steel 304 is the most popular variety of steel and is composed of 18% chromium and 8% nickel. This type cannot be hardened by heat treatments. Sometimes this steel is referred to as 18-8.
- Stainless Steel 316 is the second most popular steel. For this type, the amount of chromium decreases to 16%, the nickel content goes up to 10% and molybedum is added in a concentration of 2%.This combination gives the steel an increased resistance to salt water corrosion.
- Stainless Steel 410 is an alloy with a chromium composition of 11.5%. Because it has less chromium, it has better corrosion resistance.
- Stainless Steel 409 has the lowest concentration of chromium, 10.5%.The corrosion resistance is similar to Stainless Steel 410.
