We have begun to notice an iridescent bluish/grey staining on our surgical instruments. What would cause that, and how can we fix this problem?
First off, have your water quality checked, the culprit of that bluish/grey stain is most likely a high silica level in your water. Silicates are one of the most common minerals found on earth,(quartz, sand and glass are all silicon dioxide) and with water being a “universal solvent” it is no wonder that water running over the earth’s surface can contain high levels of silica. The deposits it leaves on surgical instruments is usually, as you described, an iridescent bluish/grey or snake skin pattern and are most common with neutral pH wash cycles or alkaline wash cycles with no or insufficient neutralization in the rinse cycle of the Washer/Disinfector. If you are already using Deionized water throughout your W/D wash cycle, the silicates can come from silicic acid slippage from an overused, exhausted DI system that probably needs to be changed more frequently. If you are only using DI water in your final thermal rinse, you might try adding an acid rinse cycle prior to the final thermal rinse to help stop these silicate deposits. (no, the acid will not harm your instruments if dosed properly, please see http://www.potomaclabs.com/education/2011/12/we-use-only-neutral-ph-enzymatic-detergent-in-our-facility-why-would-we-want-to-use-an-acid-rinse-in-our-washer-disinfector-if-we-are-not-washing-with-an-alkaline-won%e2%80%99t-the-acid-rinse-harm-o/)
If you do not use DI water at all in any part of your wash cycle, I suggest you somehow convince your institution to invest in a Deionizing system. Silica and other mineral deposits are a common cause of the corrosion of surgical instrumentation. If the process is not “nipped in the bud” your facility will constantly be investing in instrumentation that could have been in service much longer.
Silica deposits on instrumentation