Avoiding corrosion of galvanized steel structures with aluminum parts and SS washers 2

[EnergyProfessional]

For solar systems (and other roof structures) there typically is a galvanized steel substructure and the panels and standup legs of solar panels are of aluminum. Typically we require stainless steel screws and washers etc. for all connections.

now I read this galvanic chart and it seems Stainless steel may make aluminum corrode. not sure if in practice this actually is a problem. typically we have problem with non-SS parts to corrode.

what would be a proper method to connect galvanized steel and aluminum? There typically is a bolt, screw, and washer. The bolt, unless it would have a plastic sleeve always will touch both metals somewhat. So galvanic separation seems impractical (this must be structurally sound) Or am I over-thinking this?

 

[moltenmetal]

Using stainless fastener parts in this transition is about as good as you're going to get. The fastener (which is physically small and under stress) is less likely to corrode away, which is important to the joint remaining strong. There's more aluminum around, and unless the part is immersed continuously, you're unlikely to see the aluminum corrode through.

A through bolting arrangement can be electrically isolated with plastic washers and sleeves but I'd personally consider that to be overkill in a service which is wetted by rainwater only.

 

[TVP]

Stainless steel fasteners are the standard for this type of application:

http://www.ejot-usa.com/assets/files/EJOT Solar Fastening Systems_Catalog.pdf

http://www.elcoconstruction.com/Products/Flex-Technology/Metal/AllFlex2

 

[EnergyProfessional]

thanks so much, really helpful