Steam steriliser guide to removing stainless steel corrosion during aseptic processing
The Sterile Processing Department (SPD) must inevitably deal with stainless steel corrosion, also known as rust. Corrosion in steam sterilisers is caused by a chemical reaction between moisture and stainless steel. Although corrosion is often a poorly understood problem by many, it is important to remove it to prevent costly repairs.
If left unaddressed, steam steriliser corrosion can
Cause contamination and lead to load failures
Increase equipment downtime and unscheduled repairs
Require costly replacement earlier than planned
What is stainless steel corrosion (rust)?
Did you know? The fact is that stainless steel can still get dirty. It would be more true to its name if it were called stain-resistant steel. When the passivation layer on its surface is damaged, eroded or interrupted, the iron underneath can begin to oxidise causing staining.
Stainless steel corrosion, also known as "rust", describes the various discolourations of the surface. The colour depends on the amount of oxygen to which the surface is exposed. Corrosion inside steam pipes is usually black, while corrosion in autoclave chambers is more commonly a reddish brown colour on the walls. Whether it is pure water, ultra-pure water, steam or simply tap water, rust can occur from any water or moisture that accumulates on the surface.
As corrosion is caused by a chemical reaction between moisture and stainless steel, this is an unavoidable effect. Enhancing the corrosion resistance of stainless steel equipment and removing rust at the outset should be an important part of any preventive maintenance programme in the aseptic processing sector.
What is the best way to reduce the formation of stainless steel rust?
Minimise contact with water and moisture. Although this may sound difficult, remember that autoclaves use dry steam in their cycles. "Wet steam" may indicate a problem with your equipment and, if left unaddressed, may lead to load failure.
Avoid using chemicals that may affect the passivation layer of stainless steel. Abrasive chemicals can scratch the surface, while harsh cleaning products such as bleach can damage the protective layer
Implement routine maintenance procedures for rust removal and passivation of steam generation system components. Regular removal and corrosion prevention will ensure that equipment downtime is minimised.
How to tackle stainless steel corrosion
As corrosion is inevitable over time, it should be addressed quickly once it has occurred to prevent further corrosion and to keep the equipment operating efficiently. Typical procedures for descaling and passivating stainless steel equipment include
Determining the cause of corrosion by obtaining a laboratory-based assessment. Depending on the cause, a water quality analysis can provide insight into how to prevent future corrosion.
Cleaning with an alkaline solution to remove organic residues Acid treatment can be used to remove iron oxide
Adding a protective layer to prevent further corrosion
Removal of rust and rust stains from stainless steel
As rust is a form of iron oxide, chemicals that break down iron oxide will remove the rust. This process, known as deodorisation, should be tailored to the specific type of corrosion and may involve chemicals that require personal protective equipment, so it is recommended that proven professional methods are used for successful deodorisation.
