Installing Screws into Galvanized Steel 1

[KootK]

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?

 

[ToadJones]

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.

 

[ToadJones]

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.

 

[Ron]

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

 

[KootK]

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

 

[ToadJones]

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

 

[ToadJones]

in fact.....

http://www.galvanizeit.org/images/uploads/publicationPDFs/D-PGAF-05.pdf

 

[ToadJones]

see page 18

 

[KootK]

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

 

[apsix]

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

 

[dik]

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

 

[ToadJones]

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.

 

[dik]

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