HSS corrosion prevention

[RabitPete]

What is typically done to prevent corrosion on the inside of HSS columns? Structure is not exposed to elements, and top ends are uncapped. Client is concerned they will rust from inside out.

 

[HTURKAK]

You may consider the options of capping the HSS elemnts or may be better filling with concrete ?

 

[SlideRuleEra]

RabitPete - Hot dip galvanize.
I agree with your client, there are certain applications where I would not and did not use them, even with HDG. Examples are are high corrosion areas such as coastal (salt air), industrial where long life is important, and high loads where inability to easily verify internal condition can lead to sudden, unexpected consequences because of loss of section.

 

[RabitPete]

It is in industrial environment and the reason for no end caps in a 1st place is client's desire to look inside the columns to inspect their condition. He was surprised to see the fabricator has not primed them all the way down, just a little overspray.

 

[Settingsun]

Not exposed but industrial. Is it a benign environment for corrosion?

This is an old document but matches my own experience. Sealing prevents corrosion. Galvanising is fine in the right environments. Inspectability of open sections is a virtue only if maintenance is actually done, otherwise you're just watching two surfaces corrode instead of one. I see the situation as analogous to reinforced concrete.

https://www.aisc.org/globalassets/a...osion-of-structural-steel-closed-sections.pdf

 

[RabitPete]

yes, its pretty benign environment, inside of an air conditioned plant. The owner is just being really picky and comes up with all sort of weird requests and complaints. Not really feasible/cost effective to HDG those at this point (they are already primed and erected), so I am thinking of suggesting concrete/grout fill. Columns are 8x8x3/8. It will probably take over a century for those to rust through even outdoors.

 

[bugbus]

Painting the inside is an option.

I job I was involved in recently was a HDG frame made of circular hollow sections. Unfortunately, after the galvanising was inspected, there were some ungalvanised areas on the insides of the tubes that needed to be repaired.

Instead of galvanising a second time, the fabricator opted to paint the inside surfaces of the tubes with a zinc rich epoxy paint. As the tubes were several metres long, they had to insert a special sprayer on rollers through an access hole, and sprayed the inside while pulling it back out. It seemed to be quite effective.

Concrete/grout filling seems like it could trap water in the small gap that would form between the tube and the concrete/grout as it shrinks. This may be even worse than leaving it unfilled as there is no opportunity for it to dry.

 

[GGedge]

"......its pretty benign environment, inside of an air conditioned plant...."

In that case the corrosion risk is negligible because the likely time of wetness of the surface will be zero or very close to it. No need to do anything.

Cheers
GG