Certified Ophthalmic Medical Technologist (COMT) Practice Exam

Which of the following metals is NOT commonly used in the composition of stainless steel instruments?

1. Molybdenum

2. Aluminum

3. Nickel

4. Chromium

The correct answer is: Aluminum

Stainless steel is an alloy predominantly composed of iron, along with varying amounts of other metals that enhance its properties. In the case of stainless steel instruments, nickel, chromium, and molybdenum are commonly included because they contribute to the alloy's resistance to corrosion and overall strength. Nickel improves the ductility and toughness of stainless steel, while chromium adds to its corrosion resistance and helps form a protective oxide layer on the surface. Molybdenum is included for its ability to enhance strength at high temperatures and further improve corrosion resistance, particularly against chloride environments. Aluminum, however, is not typically found in stainless steel compositions. While it is a well-known metal used in other alloys such as aluminum alloys — due to its lightweight and corrosion-resistant properties — it does not contribute to the formation or enhancement of stainless steel. As a result, aluminum is not commonly used in the production of stainless steel instruments, whereas the other metals listed play significant roles in defining the characteristics and usability of stainless steel.