In the pharmaceutical industry, stainless steel is used primarily for its resistance to corrosion. High temperature and chloride environments are the most common causes of corrosion, but materials in pharmaceutical production face other challenging conditions such as high pressure, high-purity water environments and fierce cleaning regimes. Exposure to these conditions can result in various types of material degradation such as chloride stress-corrosion cracking, pitting corrosion, crevice corrosion, corrosion of weld heat-affected zones, and corrosion of welds. Any kind of corrosion can lead to drug contamination which in turn would necessitate the discarding of an entire batch of the final product, causing a considerable financial loss to the manufacturer. To avoid such scenarios, let alone those involving health risks for drug consumers, regulating authorities around the world are implementing demanding performance requirements. In the U.S., for example, Title 21 of the Code of Federal Regulation, which governs the rules for food and drugs, states:
“Equipment shall be constructed so that surfaces that contact components, in-process materials, or drug products shall not be reactive, additive, or absorptive so as to alter the safety, identity, strength, quality, or purity of the drug product beyond the official or other established requirements.”
Regulations like this one have typically led to the specification of grade 316L stainless steel for most pharmaceutical and biotechnology applications. However, specific conditions and environments oftentimes require corrosion resistance higher than that exhibited by 316L. The latest issue of Stainless Steel World News (January/February 2016) features two interesting and highly informative articles** on high-performance stainless steel grades containing either or both molybdenum and nickel and capable of withstanding harsh environments of the (bio)pharmaceutical industry. Both chemical elements are well-known for their high corrosion resistance, among other beneficial properties, and are used in many stainless steel alloys. The two articles are contributions from the International Molybdenum Association (IMOA) and the Nickel Institute (NI), two global and non-profit associations promoting the use of molybdenum and nickel, respectively, in appropriate applications.
Among the alloys discussed are 2205 duplex stainless steel, 6Mo, Alloys 22, C-276 and 625 as well as 317L and 904L. To learn more about their properties and benefits for pharmaceutical applications, read the full articles: Duplex Stainless Steel in Pharmaceutical Industry by IMOA and What the Doctor Ordered by NI.
Feature photo: Duplex stainless steel equipment in a pharmaceutical clean room. Photo by istockphoto/xxapril