What’s Your Instrument Made Of? The Science Behind Stainless Steel Tools

There are over 400 types of stainless steel. Stainless steel is an alloy and is man-made. Most surgical instruments are made from 4/20 (four twenty) grade stainless.  

Its salient characteristics are its 14% chromium content which gives it its “stainless” properties. 4/20 is magnetic, due to its iron content which can of course rust.  

A process called passivation (a nitric acid mix) is used to etch away the surface iron molecules, until the chromium molecules arrive at the surface. This ultra-thin layer of chromium prevents moisture coming into contact with the iron molecules – preventing surface rusting – this is also why you should not engrave instruments. This would break the passivated layer, therefore causing rusting at the engraving site. 

Joints are more likely to produce rust deposits since the joint action wears away the passivated layers especially if not lubricated. The passivation treatment is also less likely to deeply penetrate the joint crevasses. 

For lubrication, Bailey Instruments recommend Premixslip as it is steam penetrable and steam sterilizable. Premixslip is also a rust inhibitor and can be used to free stiffened joints. 

You can find it here: Premixslip Spray 500ml – Bailey Instruments