Surgical steel, most commonly the 316L grade of stainless steel, is an alloy relied upon heavily in medical settings for its strength and resistance to corrosion. Since it is fundamentally a metal, the answer to whether surgical steel conducts electricity is unequivocally yes. The true complexity lies not in its ability to conduct, but in the specific degree of that conduction and the implications this has for its use in the human body.
Composition and the Mechanism of Metallic Conduction
Metals conduct electricity due to metallic bonding, which involves a “sea” of delocalized electrons. These outer-shell electrons are not bound to any single atom and are free to move throughout the metallic structure. When a voltage is applied, these free electrons flow easily, creating an electric current.
Surgical steel is an alloy composed primarily of iron, mixed with significant amounts of chromium, nickel, and molybdenum. The specific proportions of these elements, such as 16% to 18% chromium and 10% to 14% nickel in 316L steel, dictate its properties.
These alloying atoms disrupt the highly ordered crystalline lattice structure of pure iron. This disruption interferes with the smooth flow of delocalized electrons, causing them to frequently collide with the foreign atoms. This resistance to electrical flow is known as resistivity, and the presence of alloying agents significantly increases the resistivity of surgical steel compared to a pure metal.
How Surgical Steel Compares to Other Conductors
Despite its ability to conduct electricity, surgical steel ranks near the lower end of the scale compared to pure metals used in electrical applications. The electrical conductivity of 316L stainless steel is typically in the range of 1.3 x 10^6 to 1.8 x 10^6 Siemens per meter. In comparison, a highly conductive metal like copper has a conductivity of approximately 5.96 x 10^7 Siemens per meter.
This means copper is roughly 30 to 45 times more conductive than surgical steel. The high resistivity of surgical steel is a direct result of the complex alloy structure necessary to achieve corrosion resistance.
Pure iron, the primary component of steel, is significantly more conductive than its alloyed counterpart, stainless steel. The intentional addition of chromium and nickel sacrifices electrical conductivity to gain superior resistance to rust and pitting. This makes surgical steel a poor choice for efficient electrical transmission, but its relatively high resistivity is beneficial in medical contexts.
Practical Implications in Medical and Body Applications
The moderate conductivity of surgical steel has significant consequences in medical procedures, particularly those involving high-frequency electrical currents. In electrosurgery, the metal tip of the instrument acts as the active electrode, conducting an alternating current to the tissue to cut or coagulate.
The instrument’s relatively high electrical resistivity prevents it from heating up excessively compared to the tissue itself. The current density is concentrated at the tip of the electrode, causing the tissue to heat up rapidly. This allows for precise and localized tissue effects without overheating the entire surgical tool.
In the context of piercings and body jewelry, conductivity presents a localized burn risk during procedures like defibrillation or electrocautery. If an electric current passes through the body, jewelry can become an unintended pathway. The small surface area of a piercing concentrates the electrical energy, which can cause severe localized heating and burns at the contact point with the skin.
The concern with surgical steel implants during Magnetic Resonance Imaging (MRI) is less about electrical conductivity and more about magnetism. While 316L surgical steel is generally considered non-magnetic, cold-working can induce slight magnetism. The metallic nature of the implant is the root cause of potential issues like image distortion or the rare risk of movement or heating due to the powerful magnetic field.