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Installing Screws into Galvanized Steel

Installing Screws into Galvanized Steel

Installing Screws into Galvanized Steel

(OP)
Is it okay to install galvanized screws into galvanized base metal?  Or does this cause potential corrosion issues?

I'm planning to do this with a small gasket between the screw head and the base metal in an attempt to limit moisture ingress into the screw hole.

I know this is a no-no for field drilling full sizee bolt holes into galvanized steel.  My gut tells me that some small screws would be okay though.

Any thoughts?

RE: Installing Screws into Galvanized Steel

Self tapping galvanized screws?
I have a publication here that states : "while chasing or retapping nuts after galvanizing results in an uncoated female thread, the coating on the engaged male thread will protect both components from corrosion".
In the case of a self tapping screw, however, my guess would be running the screw in will ruin the galvanizing on the male component also.   

RE: Installing Screws into Galvanized Steel

My point was, some claim that even if the threads on just one engaged part are galvanized, it should suffice for the protection of both parts.  

RE: Installing Screws into Galvanized Steel

The zinc coating on the screws is so malleable that it will smear on the threads and protect them somewhat...both male and female.

RE: Installing Screws into Galvanized Steel

(OP)
Thanks Toad.  Any chance you'd wanna share the title of that publication?

RE: Installing Screws into Galvanized Steel

"The Design of Products to be Hot-Dipped Galvanized After Fabrication"
American Galvanizers Association
I think it can be had for free on line.  

RE: Installing Screws into Galvanized Steel

see page 18

RE: Installing Screws into Galvanized Steel

(OP)
Thanks for the document toad.  It's a good resource in geneal.

RE: Installing Screws into Galvanized Steel

It's similar to cutting gavanised sheet with snips.
The theoretically ungalvanised edge doesn't seem to suffer from premature corrosion.

RE: Installing Screws into Galvanized Steel

Thanks, toady... have done a fair amount of research in the last couple of years on coating systems and corrosion protection.  The little article has a lot of useful information in just a few pages.

Much appreciated, Dik

RE: Installing Screws into Galvanized Steel

Glad I could help....the Galvanizeit.org website has been very helpful on a few recent jobs of mine.
There is a lot of little things to get right when you get to the detailing portion of a job involving galvanized assemblies.  

RE: Installing Screws into Galvanized Steel

galvanised and galvanised as Ronnie noted is OK... doesn't require 100% coating to provide cathodic protection... problems happen with stainless and galvanised or other things...

Dik

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