Corrosion performance check — Aluminium bronze Evaluate the statement for materials selection: “Aluminium bronze exhibits high resistance to corrosion (including many marine environments).” Is this generally true?

Introduction / Context:Aluminium bronze (Cu–Al, often with Ni/Fe) is a premier corrosion-resistant copper alloy used in seawater valves, pump components, and propellers. Designers frequently pick it over plain brasses due to improved resistance to biofouling, stress corrosion, and general attack in chloride-bearing waters.

Given Data / Assumptions:

• Typical compositions: 8–12% Al with possible Ni/Fe additions.
• Service: seawater, brine, and industrial cooling waters.
• Correct heat treatment and cleanliness assumed for best performance.

Concept / Approach:Al additions promote formation of a tough, adherent alumina-rich passive film on the copper surface. This film stabilizes in aqueous chloride environments better than the films on most brasses, giving aluminium bronze superior general corrosion and erosion-corrosion resistance. Nickel aluminium bronzes further enhance strength and cavitation resistance, making them a standard choice for propellers and seawater pumps.

Step-by-Step Solution:

Verification / Alternative check:Marine material standards list nickel aluminium bronze grades (e.g., for propellers) because of their superior seawater resistance compared to brasses; dezincification is not a concern as Zn content is minimal.

Why Other Options Are Wrong:

• Temperature and plating restrictions are unnecessary generalizations.
• Anodising is not required; natural passivation suffices when alloyed and processed correctly.

Common Pitfalls:Confusing aluminium bronze with high-zinc brasses that suffer dezincification; neglecting weld procedure control which can affect corrosion locally.

Final Answer: