Correctly evaluating surface changes – today: water stains caused by limescale

In practice, changes can occur on the Surface of medical devices over time due to mechanical, chemical, and/or physical (e.g. thermal) influences. The causes of these surface changes, if they have not already been caused during use, are usually to be found in the reprocessing process. If surface changes occur, it may be necessary to proceed in a systematic sequence to eliminate and avoid them:

• Determine the type, origin, and cause

• Assess the risks

• Implement the manufacturer's recommendations for elimination, if necessary

• Initiate preventative measures, followed by a requalification if necessary

The above-mentioned systematic approach is used to describe the most common surface changes in metallic instruments made of stainless steel (SR steel) and/or plastic or rubber products.

Water stains caused by limescale on metal surfaces

This type of coating or discoloration appears milky white to gray. Depending on the situation, these stains can be flat or irregularly shaped with sharply defined edges on the surface of the instrument and distributed throughout the washer-disinfector.

Type of surface changes origin and causes

Water stains often indicate that the water used in the cleaning step or the final rinse water has an excessively high lime content.

Recommendations for removal

One way to remove the stains is to rub them with a clean, lint-free cloth. Acidic basic cleaning can also be carried out using a special cleaner recommended by the manufacturer of the instruments/ W&D concerned.

Preventative measures

These water stains caused by lime can be largely avoided by using softened water in the cleaning step and, if necessary, intermediate rinses. The final rinse must be carried out with fully desalinated water to prevent stains from forming during machine preparation.

Assessment of possible risks

Depending on the water composition, the formation of deposits can lead to corrosion damage.

Discover more? Then read today in chapter 12 of the current red brochure:

https://www.a-k-i.org/product-page/test-pdf-brosch%C3%BCre

About the author

Aaron Papadopoulos has been a member of the AKI since 2018 and is one of the representatives of process chemical manufacturers in the group. He works within Ecolab Germany GmbH in Strategic Marketing for endoscopy and instrument reprocessing in the Healthcare Division.