Which factor is identified as a concern for patch welds in corrosion-prone areas?

Which factor is identified as a concern for patch welds in corrosion-prone areas?

• A. Elastic Modulus
• B. Weld Strength
• C. Surface Finish
• D. Crevice Corrosion

Answer: (D)

Crevice formation at the interface of a patch weld creates a sheltered microenvironment where fluids can become trapped. In corrosion-prone areas, this trapping leads to crevice corrosion, a localized attack that thrives in narrow gaps and seams where solution stagnates and oxygen diffusion is limited. The crevice becomes a microcell: the metal inside the crevice tends to corrode anodically while the surrounding exposed metal remains relatively protected, and this effect accelerates in environments containing chlorides or other aggressive species. So, the main concern with patch welds in such areas is the susceptibility to crevice corrosion. Elastic modulus is about stiffness, not a corrosion mechanism. Weld strength concerns structural integrity but doesn’t identify how corrosion initiates at a patch. Surface finish can influence corrosion rate to some extent, but the specific, characteristic failure mode introduced by patching—in corrosion-prone zones—is crevice corrosion, driven by trapped fluids and differential aeration at the patch/interface.

Crevice formation at the interface of a patch weld creates a sheltered microenvironment where fluids can become trapped. In corrosion-prone areas, this trapping leads to crevice corrosion, a localized attack that thrives in narrow gaps and seams where solution stagnates and oxygen diffusion is limited. The crevice becomes a microcell: the metal inside the crevice tends to corrode anodically while the surrounding exposed metal remains relatively protected, and this effect accelerates in environments containing chlorides or other aggressive species. So, the main concern with patch welds in such areas is the susceptibility to crevice corrosion.

Elastic modulus is about stiffness, not a corrosion mechanism. Weld strength concerns structural integrity but doesn’t identify how corrosion initiates at a patch. Surface finish can influence corrosion rate to some extent, but the specific, characteristic failure mode introduced by patching—in corrosion-prone zones—is crevice corrosion, driven by trapped fluids and differential aeration at the patch/interface.