（3）Copper and Copper Alloys

Copper is highly corrosion resistant to fresh and sea waters. But many copper alloys have been developed to supplement copper's physical properties and shortcomings such as impact corrosions by corrosion resistant surface layer being destroyed from being exposed to high speed sea/fresh water flow.

Brass

A copper alloy with zinc added, used on condensers for power generating stations. There are many different copper alloys.

Red-brass

A brass alloy with 15% zinc added. Impact resistance is relatively low.

7-3 Brass

A brass alloy with 30% zinc. Impact resistance improves as the zinc content increases, but dezincification (lost zinc) corrosions occur in sea/fresh waters

Naval Brass

A copper alloy with 1% tin added to prevent dezincification corrosion. There are some variants with minute amount of arsenic, antimony, and phosphorus.

Muntz Metal

An alloy with 40% zinc. Impact corrosion resistance is high but dezincification corrosion resistance is low.

Aluminum Brass

Zinc 22%, copper 76%, aluminum 2%, minute amount of arsenic

Cupronickel

An alloy with 10~30% nickel added. High in sea water corrosion resistance.

Copper, muntz metal, naval brass are used for fresh water condensers. For sea water condensers, aluminum brass (zinc 22%, copper 76%, aluminum 2% with a small amount of arsenic, and cupronickel are used.

(4) Aluminum and Aluminum Alloys

In aluminum and AL alloy usage environments, pure aluminum shows the highest corrosion resistance. However, pure aluminum is soft and has low strength thus variety of aluminum alloys are developed for improved physical strength. But higher strength aluminum alloys are low in corrosion resistance performances.

There are high strength aluminum alloys for the strength and corrosion resistance focused anti-corrosion aluminum alloys. The anti-corrosion aluminum alloys have alloying elements such as magnesium to suppress the corrosion resistance from degrading.