What type of plating is restricted in components without purchaser consent due to concerns over hydrogen embrittlement?

• A. Nickel plating
• B. Gold plating
• C. Cadmium plated
• D. Zinc plating

Answer: (C)

Hydrogen embrittlement is a significant concern in metallurgy, particularly when it comes to plated materials that are intended for use in structural or load-bearing applications. Cadmium plating is restricted in components without the purchaser's consent because this type of plating can release hydrogen during the plating process. The trapped hydrogen can lead to cracking and embrittlement of the substrate material, especially under stress.

In the context of API 650, which addresses the standards for welded tanks for oil storage, avoiding the risk of hydrogen embrittlement is critical to ensuring the integrity and longevity of storage tanks. The need for purchaser consent highlights the importance of making informed decisions about the materials and surface treatments used, particularly in environments that may involve pressure or stress to the structures.

The other plating types listed, such as nickel, gold, and zinc, do not have the same level of risk associated with hydrogen embrittlement, which is why they are not similarly restricted. This demonstrates the unique risks attributed to cadmium plating in contexts that require high reliability under cyclic or sustained loads.