Galvanic Worries?

[Krustynuts]

I'm planning on through bolting some stainless chain to some plain steel pipe bollards outside. There will be some stainless parts, washers and shouldered eye-bolts (probably 304) in direct contact with the steel pipe. The whole pipe setup will also be concrete filled.

Will the pipe tend to corrode where the stainless is in contact? We are also hanging some signs onto the stainless chain with brass S-hooks. Will those also corrode?

This is in the Tampa area, close to the coast, so will have humid, possibly salty air. We'd like these things to last 20+ years if possible. Not so worried about the sign hook, those will need replaced due to simple damage before corroding, but I'd hate for the bollards to look like crap after a few years.

 

[EdStainless]

Your steel pipe will not like this. Yes, the threads will corrode and you will loose your chains.
If this is near the water (can you see it from there?) 304 will not cut it for long term service.

Do you really care what it looks like? If it bleeds rust is it OK? If so then all galvanized steel might be a better bet. Just let it rust. If you make it heavy enough it will last.

Often ballards that you see are plastic or stainless caps over filled steel pipe. This keeps the total cost down. If you make stainless caps do not make the tops flat. They need to be domed enought for water to run off and for birds to not like to land on them.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[Krustynuts]

OOps, the stainless is 316! The site is not right on the water, but it is probably within 2 miles of it. The stainless threads will corrode, or the steel pipe?

 

[Metalguy]

The steel pipe is likely to corrode close to the SS--it's the anode. 304 SS MIGHT develop pits, while 316 has more resistance to such pitting.

 

[Krustynuts]

Any way to prevent this? Some type of non-metallic washer between the CS pipe and SS?

 

[EdStainless]

How are you going to keep the steel pipe from rusting? You could weld a 316L ring or stud to the pipe. You would have to make sure that the weld was painted like the rest of the pipe or it would corrode easily.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[Krustynuts]

The pipe is a safety bollard, so the whole exterior will be painted yellow. Inside is filled with concrete. I bascially have a threaded stainless rod going through both sides of the pipe. On the inside of the pipe, there will be stainless washers and nuts snugged against the inside of the pipe to keep the rod in place. A non-metallic washer could be placed between the stainless washer and CS pipe.

On the outside, a shouldered lifting eye-bolt will be threaded onto the exposed stainless rod. The paint will help on the outside, but I thought another non-metallic washer could be used between the eye-bolt and CS pipe.

 

[EdStainless]

In order for isolation to work there can be no contact between the two metals. You will need a non-metalic washers with flanges and over sized holes. You will need to seal all of the crevices also.

Do you really want to use threads? Do these need to be removable?

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[Krustynuts]

The chains, etc., will get beat up over time, so we figured that something completely removable would be better. We could even remove the threaded rod and replace it if we tried hard enough!

 

[ENEPPA]

Can you get pipe or threads Electroless nickle plated. You could EN plate any welds and you would not have a plodlem with threads corroding, And maybe you should try passivating your threaded rod will electropolish first to pull any remaining iron out of the steal.