Fayed surfaces are concerning in chemical cleaning due to the risk of:

Fayed surfaces, which are the interface between two materials that are in contact, can lead to issues during chemical cleaning because they have the potential to trap contaminants and corrosive materials. When these surfaces are not properly cleaned, the entrapped substances can lead to corrosion, which can compromise the integrity of the materials involved and cause further degradation over time. This is particularly concerning in systems where chemical reactions or processes can produce harmful by-products that would exacerbate corrosion if not adequately removed.

In the context of the cleaning procedures, it is critical to ensure that all surfaces, especially fayed surfaces, are thoroughly cleaned to prevent contaminants from being trapped. Failure to address this can lead to longer-term maintenance issues and increased risk of failure in the equipment. The other options, while related to material interactions, do not directly address the specific risks associated with fayed surfaces in the context of chemical cleaning.