API 571 Certification Practice Test 2025 – Complete Exam Prep for Corrosion & Materials

Phosphorus-inhibited alloys are specifically designed to improve their resistance to dealloying, a form of corrosion where one metal is leached from the alloy, potentially leading to structural weakening. The addition of phosphorus modifies the microstructure and enhances the corrosion resistance of the alloy, particularly in environments where dealloying might occur, such as in certain chloride-rich environments.

In comparison, while chromium nickel alloys can offer good corrosion resistance, they are not specifically tailored for dealloying resistance as phosphorus-inhibited alloys are. Ceramic alloys primarily focus on different properties, such as high heat stability and hardness, rather than dealloying resistance. Silicon-containing alloys can have some desirable properties, but they are also not primarily developed for dealloying resistance. Thus, phosphorus-inhibited alloys are the most effective choice for enhancing resistance to this particular type of corrosion.