Though stainless steel in highly resistant to corrosion and rust, however they require regular maintenance to ensure that the instrument will not stain or rust.
Most Durrani & Co. instruments are manufactured using stainless steel type 420 for scissors and 410 for forceps, while the hollowware is manufactured using stainless type 304.
Stainless steel differs from carbon steel by the amount of chromium present. Unprotected carbon
steel rusts readily when exposed to air and moisture. This iron oxide film (the rust) is active and accelerates corrosion by forming more iron oxide. Stainless steels contain sufficient chromium to form a passive film of chromium oxide, which prevents further surface corrosion and blocks corrosion from spreading into the metal’s internal structure. Passivation only occurs if the proportion of chromium is high enough.
| Carbon | 0.17-0.25% |
| Silicon | ≤ 1.0% |
| Manganese | ≤ 1.0% |
| Phosphorous | ≤ 0.045% |
| Sulphur | ≤ 0.043% |
| Chromium | 12.0-14.0% |
During the manufacturing process, every effort is made to ensure that the instruments are corrosion resistant. However, if not properly maintained, stainless steel can rust and stain, reducing the life of the instrument or rendering it useless. For more detailed information on instrument care, see our Instrument Care & Cleaning instructions.
Heat Treatment
Heat treating makes the instruments hard and enables them to withstand rigorous use. Stainless steel is brought to a very high temperature and then cooled until it has reached the proper hardness. Hardness is measured in units called Rockwell Hardness (HRc). A typical hardness range for needle holders is HRc 40-48. For scissors, the range is HRc 50-58.
Heat treating and steel selection are just two of the more than 80 steps required to produce surgical instruments to Durrani & Co. surgical standards. We monitor and verify the accuracy of our manufacturing process through frequent audits.
See Making of a Surgical Instrument for some of the steps required.