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Metal / Stains - Silicates and Other Mineral Compounds

Type of Surface Change

Yellowish-brown to blue-violet discolorations of various forms, ranging from extended and rainbow-like tarnish to colored spots or droplet-shaped stains.

Origin & Causes        

  • Silicic acid leakage in the production of fully demineralized water when using ion exchangers and reverse-osmosis water treatment plants.
  • Carry-over of cleaner residues containing silicates into the final rinse in machine-based treatment processes.
  • Other mineral substances (e.g. copper) contained in the final rinse water of mechanical cleaning processes or in the steam condensate.

Treatment Recommendations        

  • Mineral deposits can be removed by acid-bases cleaning using special detergents as recommended by the manufacturer.
  • Stubborn deposits (silicate build-up) can be removed with agents containing hydrofluoric acid, or through mechanical surface treatment by the manufacturer or a qualified repair service provider.

Preventive Measures        

  • Use silicic acid-free, fully demineralized water for final rinse in machine-based processing.
  • Prevent cleaner carry-over by:
  • correct tray loading and proper positioning/fixation of items with hollow spaces in which liquids can accumulate (e.g. kidney-shaped bowls).
  • Ensure sufficient neutralization and intermediate rinsing in mechanical cleaning processes.
  • Use water quality as specified in EN 285 (Annex B, Table B.1) or DIN 58946, Part 6, for steam sterilization.
  • Ensure correct functioning of your dosing equipment.

Risk Assessment        

  • No corrosion, only aesthetic effect; no hygienic hazards.
  • The laser-lettered labels of instruments may be adversely affected (bleached) when treating them with acid-based cleaners. This may result in poor legibility, thus impairing or even destroying their coding function.