Dissimilar Metals Touch at an Exterior Duct Support
Verify the specified isolation material and support detail before allowing incompatible metals to remain in direct contact, especially where moisture can collect.
This aluminum duct is bearing directly on a galvanized support and the detail shows an isolation layer that is missing. Can we verify the approved pad and fastener arrangement before final tightening?
Watch out
Do not improvise isolation with cardboard, random tape, or material that absorbs water or degrades outdoors.
Check
Identify both metals and their coatings.
Inspect for existing staining, coating damage, and trapped water.
Check the support detail for pads, sleeves, washers, or barriers.
Verify compatible fasteners and sealants.
Steps
Identify both metals and their coatings.
Inspect for existing staining, coating damage, and trapped water.
Check the support detail for pads, sleeves, washers, or barriers.
Verify compatible fasteners and sealants.
Say this to your foreman
This aluminum duct is bearing directly on a galvanized support and the detail shows an isolation layer that is missing. Can we verify the approved pad and fastener arrangement before final tightening?