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Metal / Corrosion - Stress Corrosion Cracking

Type of Surface Change

The so-called electrolytic/anodic stress-crack corrosion (or stress corrosion cracking) usually leads to visible cracks and fractures. In some cases, however, the crack - its origin and/or propagation - cannot be seen because it is hidden (in the joint of a pair of scissors, for example). Very frequently, the non-deformed (and possibly hidden) fracture surfaces are indicative of the growth of the crack (typically associated with corrosion products).

Origin & Causes        

  • This type of corrosion often affects product areas or components subject to high tensile stresses due to design and/or manufacturing reasons (such as rivet or screw connections, welded or soldered connections or so-called press/force fit connections).
  • Stress corrosion cracking can also be caused by improper repair (e.g. application of inadmissibly high straightening forces) or by
  • cleaning/processing the item in a state of high tension (e.g. when the ratchet is fully pressed down, i.e. closed).
  • The same applies to overstressed or strained instruments that are subsequently treated in a corrosion-promoting environment, especially at higher temperatures. (The main corrosion initiator is water containing chlorides, but surgical residues, drugs and the like must also be taken into account.)

Treatment Recommendations

None (cannot be corrected).

Preventive Measures        

  • Clean jointed instruments in an open condition and sterilize them with the ratchet locked in the first tooth at a maximum.
  • Reduce the chloride load to a minimum (for example, reduce surgical and drug residues; use only suitable water for cleaning, final rinse and sterilization).
  • Avoid overstressing as a result of improper handling.
  • Have your instruments repaired only by the manufacturer or a qualified and specially authorized repair service provider.

Risk Assessment        

  • For reasons of patient and user safety, withdraw affected instruments from service (and the instrument processing cycle) at once!
  • To retain the value of your instruments, eliminate the cause of corrosion!