Corrosion Protection of Fasteners

[cruzinbear]

I am installing some lightgauge steel studs (architectural) on top of an existing gas station roof (exposed). My concern is corrosion of the cold-formed steel members and fasteners. The location of the structure is in Southern California, however it is inland and in a very hot and dry climate.

For the cold-formed members I am going to hot-dip galvanize for corrosion protection.

For the fasteners I am using the following:

1) Hilti X-U low velocity fasteners (icc report 2269) they are zinc coated. This will connect the support structure to existing steel framing.

2) Buildex TEKS screws (icc report 1976) also zinc coated. This will be used to connect the lighter cold-formed framing to one another.


My question is how good are these fasteners over time? Will this stuff hold and will I have corrosion issues in the future? If so, how long before there is a structural issue? Any comments or recommendations would be much appreciated. Thank you.

 

[Signious]

Given that you are in a dry climate, and assuming the fasters come in little to no contact with liquid water I wouldn't be terrified - but there is definitely enough galvanic potential between zinc and cold formed steel for the zinc in the fasteners to be eaten away over the course of the buildings life.

I would call the steel stud manufacture and see what fasteners they suggest in regards to galvanic corrosion. They will probably ask for rubber washers at minimum.

 

[Guastavino]

Cruzinbear,

Do you have the Hilti Direct Fastening book #1. It has some great corrosion information in chapter 2. It's a free download from their website. Also, Hilti reps should be good to talk with you about that. Just because they are "zinc-coated" doesn't mean they will hold up. If you look at the hilit book, section 2.3.3.1 in my version, you can see some salt spray testing they did on some "zinc plated" fasteners. Some didn't do that well.

My advice, think long and hard about this and ask lots of different people. Don't take any manufacturer's word for it, but whatever you do say with the manufacturer, try to get them to email you it in writing. I'm always disappointed when I get a call back from a rep instead of an email. Emails are eternal, words are well, easily forgotten.

Best of luck