Cadmium Plated Bolts 1

[JAE]

Anyone ever use cadmium plated bolts? What are the structural design ramifications of using this?

 

[UcfSE]

This is a link to another forum inquiry that is similar to yours. It's a forum and so information should be taken with a grain of salt, so to speak. I'm sure you know that though .

http://www.finishing.com/4000-4199/4144.shtml

This is another article describing some basic behavior of cadmium plated bolts. Is takes a military point of view but has some good information.

http://www.pfonline.com/articles/029905.html

This article has some more properties of coatings, specifically about 1/5th of the way down the page is a section called "Properties of the Deposited Metal Coatings
"

http://www.enthone.com/resources_detail.aspx?Page=zccoatings.ascx

It appears to me that a big difference between cadmium plating ans zinc plating is the ability of the plating to resist corrosion, one metal being better than the other for a given environment. The other difference I've noticed most is the different torque requirements for tightening nuts for each metal plating type.

I'm by no means an expert, though, so others will actually have experience with this. Did you find the same links I did? ;-)

 

[Bagman2524]

I believe we used cadmium bolts in the nuclear power industry. As stated above, the difference is the ability to resist corrosion. There should be no affect on the structural properties of the bolt.

 

[JAE]

Thanks to you two. I was reviewing a specification requirement for a new project (warehouse) and saw where they were requiring cadmium coatings on all fasteners and I'd never seen that application before in "normal" buildings.

 

[Ron]

JAE...as you're aware, cadmium plating is just another form of corrosion inhibition, but a bit unusual for "building bolts", as you noted. I haven't seen any in years in that application.

One thing to be aware of is the difference in their ability to be tensioned to certain torque values relative to either HDG or uncoated bolts. They are a bit more "slippery" than either of the others, so if you torque them using a calibrated wrench method you will typically achieve required tension at lower torque values. If the testing lab is only using a torque wrench and not calibrating with a Skidmore-Wilhelm device, then they will often require torque values that they see using HDG or plain bolts, which will result in a fastener that might be overtensioned.

 

[kenvlach]

Cadmium plating resists corrosion better in most, real-world applications. However, it is frowned upon for environmental reasons.

In terms of bolting, corroded zinc-plated bolts often snap when trying to undo nuts that are seized due to formation of a voluminous white corrosion product (ZnO + Zn(OH)₂ plus sometimes carbonate) on the threads.
Never heard of this happening with cad plated.