About Barrier Tape
When using dissimilar materials in roofing and cladding it is necessary to use barrier tape to prevent galvanic corrosion or electrolytic reaction.
Barrier tape should be applied to the supporting structure before the sheets are fixed and should have a thickness of at least 0.12mm.
Most barrier tapes are self adhesive and to ensure good adhesion it may be necessary to dry the purlin flanges.
Barrier Tape General Information
The tape should be approximately 10mm wider than the flange so as to overlap each side by some 5mm and should be overlapped at joints to ensure continuity of protection.
https://www.cladco.co.uk/how-install-your-roofing-sheets
http://www.fao.org/3/s1250e/S1250E0l.htm
https://www.nationalboard.org/Index.aspx?pageID=184
https://en.wikipedia.org/wiki/Metal_fabrication
See also Portfolio outdoor lighting and affordable glass