Stainless steel equipment and furniture are often used in cleanroom environments due to their ability to meet the stringent hygiene requirements. Not only is stainless steel robust, but it is also able to withstand even the most rigorous cleaning procedures. However, just because its name has the word stainless in it does not mean that it cannot be stained.

Are you seeing stains show up on your stainless-steel after it’s been cleaned? Chances are that those stains are caused by a corrosive cleaning agent you are using in the cleaning process. So, you may ask, “Then how do I clean my stainless steel equipment and furniture while also keeping my cleanroom clean?” Hopefully, by the time you finish this article, you will have a better idea of how to properly care and clean your stainless-steel equipment in your cleanroom.

Stainless Steel needs to be kept clean for many reasons some of which are:

1. To preserve the appearance
2. Cleanroom or controlled environment disinfection
3. To preserve corrosion resistance

Stainless steel is coated with a thick layer of chromium oxide which protects the material from corrosion - but this protective layer still needs some protecting. You can safeguard this protective film by cleaning your stainless steel frequently. If you don’t clean it regularly, contamination from dirt and debris will trap corrosive agents and reduce the shield that prevents corrosion. Since stainless steel can’t be “worn down” by excessive cleaning, the more you clean the better. The key is to clean using the right cleaning agents.

First, it is important that you follow any site and standard operating procedures when cleaning your cleanroom. You should also follow the four step cleaning process for hazardous materials if you are working in an hazardous drug environment (for more information on this four step cleaning process, see Guardian’s blog article The Four Step Cleaning Process).

There are many different methods to cleaning stainless steel some of which depend on the area in which you are cleaning. Stainless steel can be cleaned with water, detergent, or solvents. For a basic clean, warm water with a gentle neutral detergent is enough for cleaning stainless steel tables, benches, stools and equipment. Use a soft lint-free cloth and warm water mixed with detergent. Disinfection can be done with either a sterile or non-sterile 70% isopropyl alcohol (IPA) depending on your cleanroom’s requirements and SOP. Cleaning and disinfecting should always be followed by a rinse with clean hot water. This will remove all oxidizing or corrosive agents from the stainless steel.

Chlorine solutions (which can cause corrosion) can remove the protective chromium oxide layer from your stainless steel surfaces. But in a cleanroom, it might be difficult to avoid using a chlorine-based cleaning agent when deactivating and decontaminating your stainless steel surfaces. That is why it is important to complete the next two steps to the four step cleaning system; cleaning and disinfecting. If you do see rust show up on your stainless steel, it is most likely because you forgot these last two steps after using a chlorine solution during decontamination.

Once rust sets in, it is not the end of the world. This can be fixed through passivation, the process of treating stainless steel with a mild oxidant such as a nitric or citric acid solution. This will remove the rust and cause the protective layer of chromium oxide to form again.

A good idea is to add passivation to your regularly scheduled cleaning routine as a preventative measure. This will help in preventing rust from forming and protect your investment in the stainless steel equipment.