What is the percentage of zinc below which copper-based alloys are generally not subject to dezincification?

In the context of marine corrosion, dezincification refers to the selective leaching of zinc from brass, which is an alloy of copper and zinc. This process is particularly of concern in marine environments where the presence of saltwater can exacerbate corrosion. The generally accepted threshold for the percentage of zinc in copper-based alloys to mitigate the risk of dezincification is below 15%.

When the zinc content is kept below this percentage, the likelihood of the alloy undergoing dezincification diminishes significantly. This is because a lower zinc concentration allows for greater copper stability, making the alloy less susceptible to corrosion processes that lead to dezincification.

Higher percentages of zinc, as reflected in the other options, increase the risk of repassivation of the copper matrix and subsequent corrosion, leading to the degradation of the metal performance. This is critical for materials used in marine applications where longevity and resistance to corrosion are paramount. Understanding this balance is essential for selecting appropriate materials for boat fittings and components exposed to seawater.