Which three elements are the principal constituents of marine grade stainless steel, in descending order?

Marine grade stainless steel primarily consists of iron, chromium, and nickel. This composition is crucial because each of these elements plays a specific role in enhancing the material's resistance to corrosion and improving its overall mechanical properties.

Iron serves as the base metal, providing structure and stability. Chromium is key to the corrosion resistance of stainless steel; it forms a protective oxide layer on the surface when exposed to oxygen, preventing rust and corrosion from developing. The presence of nickel further enhances the corrosion resistance and improves the toughness and ductility of stainless steel, making it suitable for the demanding conditions in marine environments.

This combination of iron, chromium, and nickel is what characterizes marine grade stainless steel, allowing it to withstand the harsh conditions such as saltwater exposure that can lead to corrosion in other materials.