API 571 Certification (Corrosion & Materials) Practice Test

Which corrosion method is described as "removal of Sn" from tin bronze?

1. Dealloying

2. Decarburization

3. Corrosion fatigue

4. Stress corrosion cracking

The correct answer is: Dealloying

The described corrosion method of "removal of Sn" from tin bronze refers to dealloying. This process occurs when one metal within an alloy is preferentially leached or corroded out, leading to a substantial change in the microstructure of the material. In the case of tin bronze, tin (Sn) is the component being removed, which can significantly weaken the alloy. Dealloying typically occurs in environments that promote a specific ion's dissolution, often resulting in the formation of a porous structure that can greatly reduce the mechanical integrity and corrosion resistance of the metal. This phenomenon is particularly critical in applications involving bronze, where maintaining the alloy's properties is essential for performance. Other corrosion methods like decarburization, corrosion fatigue, and stress corrosion cracking relate to different mechanisms and materials and do not focus on the selective removal of one component from an alloy. Decarburization involves the loss of carbon from steels during high-temperature processing, while corrosion fatigue refers to the combined effects of cyclic loading and corrosion that result in material failure. Stress corrosion cracking occurs when tensile stresses and corrosive environments interact to cause cracking in susceptible materials over time. Thus, these processes are distinct from the dealloying effect described in the question.