Stainless bushings in mild steel (corrosion?) 1

[MetalArtMan]

Hello,
I am the designer of a deck railing which uses stainless steel cables (cable railing)and mid steel posts which are laser cut, welded and powder coated (zinc rich epoxy primer followed by polyester top coat). Powder coating has difficulty getting into small holes (where the cable passes thru the post) so I was thinking about sleeving the holes with stainless prior to powder coating. Question is would galvanic corrosion be a problem? See pictures of the rail at:

http://keuka-studios.com/cable_railing.html

Ant hlpe would be appreciated.
Dan

 

[unclesyd]

Galvanic corrosion shouldn't be problem as the bushing doen't stay wet all the time.
I've used stainless steel/cs all around the docks and boats without any problem. I normally try to use 316 SS.
Why not powder coat an aluminum bushing?

The only problem I see with a SS bushing is that the movement/vibration of the cable hanger threaded area will tend to keep the stainless very active and you could see some minor rust, 316 SS will mediate this to some extent.

The dock part might be corroding now as Ivan (hurricane)put it under water, the boat parts will be allright as they are a 1/2 mile from any water.

 

[MetalArtMan]

Thanks for responding.
Is your recommendation of aluminum because it is less noble than CS and would become the Anode? Should I worry about the fact that stainles steel cable passes thru this aluminum bushing?
Thanks
Dan

 

[EdStainless]

The bushings just need to resist corrosion and be easy to work with. SS is overkill for them. Al will cost less and be easier to work with.
If this was going to be seeing splashing seawater all of the time then things might be different, but for this case don't worry.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[unclesyd]

EdStainless got the message I've been try to get out for an hour but IE is giving me problems.
I'll try to add more when I get things straightened out.

Great looking deck.

 

[unclesyd]

Looking at the pictures one thing I noticed was the carriage bolts that you used. They appear to be galvanized and of the mechanically galvanized type.
Your's maybe fine, but recently I've been privy to some problems with mechanically galvanized bolts and nuts. The problem was the zinc coating didn't last very long. Cursory examination revealed that some sort of binder/adhesive had been used in the mechanical galvanizing process. This made the coating more like a paint than true zinc galvanize coating. The problem with this was that the adhesive apparently wasn't UV resistant.
If they are hot dipped galvanized or SS no problem.