Can pressure-treated wood be used in contact with bare and prepainted Galvalume® sheet?

Contact with pressure-treated wood or, for that matter, any wet lumber is not recommended for either bare or prepainted Galvalume® sheet. Treated lumber contains chemicals that protect the wood when buried in soils. Direct contact between wet treated lumber and Galvalume® sheet creates a corrosion cell and the corrosive chemicals leaching out of from the wood accelerates this process. All rooftop ancillaries, such as air conditioners, should be mounted with factory-made mounting accessories compatible with Galvalume® sheet (roof curbs, for example). Some HVAC contractors commonly mount rooftop air conditioners on pressure treated landscape ties. Direct contact of these ties with the Galvalume® roof causes corrosion of the aluminum-zinc coating. Even drainage from pressure treated lumber onto Galvalume® sheet should be avoided.  more