Stainless Steel for Pharmaceutical Applications: Grades, Properties, and Best Practices

Selecting appropriate material of construction is critical for product quality, safety, and regulatory compliance, in the manufacturing industry. For the pharma industry, it must comply with various factors such as product requirements, chemical characteristics, cleanliness level, and resistance against material degradation.

Stainless Steel is a widely used material in the pharmaceutical industry for various applications. It provides an excellent option against product degradation, corrosion, and contamination. It capabilities make it an excellent choice for use it in sterile environment, preventing product contamination, and ensuring durable equipment performance. 

Different categories of stainless steel are used in the pharma industry, including SS316 and SS304. For the SS316, the low carbon content type represented as SS316L is the most common type used for pharma applications. It is mainly used in applications where the product directly touches the surface. Less critical variants are used in external layers of equipment.

Stainless Steel advantages for pharma applications

Let’s discuss some advantages of stainless steel for pharma applications

Resistance to corrosion 

Stainless steel is highly resistant to corrosion due to many chemicals, fluids, and water used in pharmaceutical applications. It also prevents metal degradation of equipment or machines used during processing, protecting equipment and products. 

The corrosion resistance is due to the presence of Chromium in the SS alloy, which forms a protective layer on the surface. The protective layer protects the surface beneath it, protecting the entire stainless steel equipment. 

Easy to clean and hygienic

Stainless steel surfaces have good surface smoothness and roughness properties. These features prevent the buildup of contaminants and bacteria on the metal’s surface, enabling efficient and easy cleaning. These features help prevent contamination in the area, product, and equipment. 

Resistance to chemical reactions

Pharma products combine different grades of chemicals with varying chemical properties. During manufacturing, these chemicals undergo different reactions with various intensities. These chemical reactions could also affect equipment such as vessels and associated piping. For these reasons, these components must withstand chemical reactions during product manufacturing. 

Stainless Steel provides good resistance to many chemical reactions associated with product manufacturing. It can withstand the effect of chemical reaction, such as color alteration and change in metallic properties, making it stable and reliable for several product manufacturing processes.

Temperature resistance 

High-temperature applications are common in the pharmaceutical industry. Examples include steam sterilization and endothermic chemical reactions during product manufacturing. High temperature processes also effects the associated equipment or its part.

Metals are sensitive to high temperatures and can affect their mechanical properties if the temperature goes beyond their acceptable range. It can deform the metallic structure or decrease its tolerance to corrosion or chemical reactions.

Stainless Steels is highly effective in resisting the effects of high temperatures. This is due to addition of 2% Magnesium, which increases the acceptable limit of temperature to higher level. This allows stainless steel to be easily used for high temperature pharmaceutical processes without material deformation and alteration. 

Stainless Steel types for pharma applications

There are different types of stainless steel used in the metal industry. However, not every kind of stainless steel can be used in pharmaceuticals.  

For the pharma industry, the 300 series of austenitic stainless steel are used for various purposes. 

300 series of austenitic stainless steel

The 300 series of austenitic stainless steel have different types, each with its specific material composition. As discussed earlier in this article, every type of stainless steel has it unique advantages and designed for specific applications.

The type of stainless steel used in the pharma industry is SS 304 and SS316.

SS 304

SS 304 is a stainless steel variant containing about 18% chromium and 8% Nickel. It is mainly resistant to the majority of chemicals. However, against some strong chemicals, such as concentrated acids or chlorine bases, the SS304 lack effectiveness. 

Another variant of SS304, 304L, is the common type used in the pharma industry. It is a low-carbon variant of SS304 that effectively reduces carbide precipitation. It is phenomenon during welding, that reduces the corrosion ability of a stainless steel.

SS 304 is used in applications where the product does not come in direct contact with the metal surface. Example of SS304 application includes outer body of the autoclave and vessels. 

SS 316

SS 316 is a class of austenitic stainless steel containing Chromium, Nickel, and Molybdenum. It is characterized by enhanced resistance to corrosion compared to other stainless steels, particularly SS 304. 

Adding Molybdenum to SS316 increases its resistance, which is not included in other forms of stainless steel. It is also best against localized corrosion, a common resistance phenomenon in chemical-related applications, where small holes or pits appear on the metal’s surface. 

Another variant of SS316, called SS316L, is widely adopted in critical pharma applications. The low-carbon variant of SS316 prevents carbide precipitation during the welding process. It is a harmful metallic effect that occurs due to carbon in metals caused by the welding process. Carbide precipitation can result in sensitization and inter-granular corrosion that can reduce the ability of the metal to resist corrosive environments. 

Due to its features, SS316L is used in critical pharma applications and areas. These metals are used in applications where the product comes in direct contact with the metal. They are also used in product manufacturing, where a chemical reaction occurs to produce the required product. Due to their high surface finish characteristics, they are also used in sterile environments.

Stainless Steel Applications in Pharmaceutical Equipment and Systems

Let’s discuss some applications of stainless steel in the pharma industry

Mixing and Blending Equipment

Mixing and blending equipment is used to mix the ingredients of pharmaceutical drugs and convert them into a product. The ingredients are in raw form with varying chemical properties, and the active is the central component that develops the required properties in the drug.

The mixer, along with other parts such as walls, ports & valves aggressively come in direct contact with these chemical ingredients during the mixing process. It is possible that these raw materials can react with the equipment body, altering the raw materials’ properties and degrading the equipment’s surface. 

Using Stainless Steel to construct mixing and blending equipment helps prevent problems related to the product’s chemical reaction and metal degradation. Stainless Steel offers resistance to various negative effects developed as a result of material and metal interaction. 

Piping and Tubing

Piping and tubing are especially useful in the pharmaceutical industry. They are used to interconnect different components of equipment, supply utility to a particular area or machine, and interconnect multiple machines with each other

The piping for pharma applications must resist corrosion, provide the material’s strength to prevent degradation, and maintain sterility. A small problem in the piping or tubing section can damage the entire network and create problems for the product and production process.

For pharma applications, piping and tubing are constructed with stainless steel since it is resistant to corrosion, thereby increasing the piping’s life. SS also offers easy cleaning without any specialized cleaning agents and maintains product purity levels.

Storage Tanks

Storage tanks store liquid products, raw materials, and water for different purposes. They are used for

• Storage during holding stage, where products await results of quality tests.

• When a filling machine is unavailable.

• Storing purified water before it is distributed in the relevant department or area. 

These applications require storage tanks to preserve product characteristics until they are filled in the containers or used by the relevant process. After storage, the tank requires cleaning to prepare for the next product or batch in order to prevent product mix-up. Lastly, the tank should show resistance to different chemical raw materials & products and prevent material degradation.

By incorporating stainless steel for storage tanks, manufacturing will solve all problems related to metallurgy. It can prevent the product’s effect of degrading metal’s surface, provide easy and effective cleavability, and prevent corrosive impact on the metal’s surface.

Some tips to improve your stainless steel component for pharma applications

Although stainless steel offers distinctive features that make it an ideal choice for pharma applications, care must also be taken to increase its life and performance. Because, like other, they do have limits and testing these limits will degrade & reduce its capabilities

Below are some tips that help to enhance the performance of stainless steel-related components in the pharma industry.

• Clean stainless steel components regularly to prevent the buildup of dirt and dust. These particles, combined with moisture, can decrease the material’s strength against corrosion and degradation.

• Always avoid strong chemicals and abrasive brushes when cleaning. These can damage the metal’s passive layer. Instead, use warm water, a soft cloth, and mild dish soap.

• After clearing, ensure no residual water, moisture, chemicals, or cleaning agent remains on the surface. 

• Mind the direction of the grain during polishing.

• Keep an eye on the early stages of degradation, such as coloration and pitting. Specifically, for areas near connections and joints

• Ensure all seals and gaskets are intact and in good condition to prevent leakage of strong solution, chemicals, moisture, dirt, and debris from outside the      equipment.

About the Author

Muhammad Asim Niazi has a vast experience of about 11 years in a Pharmaceutical company. During his tenure he worked in their different departments and had been part of many initiatives within the company. He now uses his experience and skill to write interested content for audiences at PharmaSources.com.