Most submarine seawater valves are made of an alloy of 70 percent copper and 30 percent of which substance?

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Multiple Choice

Most submarine seawater valves are made of an alloy of 70 percent copper and 30 percent of which substance?

Seawater valves need an alloy that stands up to chlorides and resists dezincification. An alloy with 70% copper and 30% nickel, known as cupronickel, fits this requirement because nickel markedly improves corrosion resistance in seawater and provides good strength while remaining ductile. That combination is why it’s widely used for submarine seawater valves. Tin would form bronze, which isn’t as resistant in seawater; zinc would form brass, which dezincifies in chloride environments; aluminum would corrode rapidly in seawater. So the 30% additive that makes this strong, corrosion-resistant alloy is nickel.

Seawater valves need an alloy that stands up to chlorides and resists dezincification. An alloy with 70% copper and 30% nickel, known as cupronickel, fits this requirement because nickel markedly improves corrosion resistance in seawater and provides good strength while remaining ductile. That combination is why it’s widely used for submarine seawater valves. Tin would form bronze, which isn’t as resistant in seawater; zinc would form brass, which dezincifies in chloride environments; aluminum would corrode rapidly in seawater. So the 30% additive that makes this strong, corrosion-resistant alloy is nickel.

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