Q. We are washing stainless medical devices in a washer and are getting water spots. We are using Solujet and Citrajet. What’s causing this problem?
A. Water spots typically occur because of two main reasons: the orientation of the parts in the washer is trapping dirty wash water and/or detergent dosing is insufficient.
If any items being washed have a shape that can retain dirty wash water, it can sometimes get carried into the next rinse cycle and spread all over all the items being washed. An example of a such a shape would be “U” shapes or cups. Then the parts gets dried and the residue from the dirty wash water leaves water spots. To solve this, load the items in a way to tilt them so they drain completely and do not carry dirty wash water from the wash cycle to the rinse cycle.
If this is not an issue, then consider detergent dosing. If you are washing with hard tap water (high in calcium, magnesium and iron), and you are under-dosing the detergent, then there may not be enough chelating agent to tie up the hardness ions. In this case, these ions will precipitate out as metal oxides/hyrdroxides/carbonates that then do not rinse easily and can lead to water spots.
Be sure to use at least a 1% Solujet® Low Foaming Phosphate Free Detergent wash solution (10 mL/L) and 1% Citrajet® Low Foaming Acid Cleaner rinse solution (10 mL/L). Also consider using deionized, RO, or distilled water for rinsing, and even washing, which can help completely avoid this problem. Note that high quality water is less important for the wash step.
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