Tube Steel Inside Corrosion 9

[jcali]

Has anyone dealt with exterior painted structural steel tubes that have begun to corrode on the inside? I've been asked about a building in coastal NJ with exposed tube steel stair framing. It's painted outside, but it is corroding from the inside out. Is there any way to repair this?

-JCali

 

[quark]

I don't know whether that is a standard practice or not but we did exactly what L775 said for one of our piperacks. We also used PUF to fill the cavity.

Regards,

 

[eyec]

repair it = $200k
replace it = $100k
it fails & someone is injured = pricele$$ (but the lawyers will try to find the right price!)

remember, you are talking about "stairs". SAFETY FIRST!

in general channel stock should be used in the elements, tube on interiors.

 

[apetr26542]

Do you know the level of corrosion on the inside? Drill holes or remove a coupon section for investigation to determine section loss. I definately agree with eyec. It is usually much cheaper to replace than repair. The level of corrosion will determine your repair solutions. If there is any question, you do not want to stick your neck out.

 

[griffengm]

JCali,
I do not see a mention of how the tube is mounted so maybe we all assumed it is welded to a framework of some sort? If it is welded "permanently", you might consider cutting out the damaged area and replacing it with a sleeve/tube that can be bolted in place.
If it is embedded in concrete, you might cut out the section, fill the hole in the concrete and work with a sleeve assembly.
Time is on the side of corrosion. A poorly finished weld or pinhole might as well be a fist sized hole if given enough time. X-raying welds on a railing post seems like overkill but
I've built a number of railings and like to leave the bottom of any tubes open wherever possible so they can drain and dry. Galvanizing or adding asphalt will improve durability but there may be aethetic reasons for not using tar.
Didn't mean to go on this long.
Good luck.

Griffy

 

[flamby]

Filling with concrete is a prudent method. Some of the other methods mentioned above sound very cumbersome.

 

[griffengm]

Jcali,
Since you already have corrosion the likelihood of ending up with no metal at all is great whether you fill with concrete or coat with something. Since you give no dimension for the post diameter the usefullness of concrete can be questionable.
How exposed to mechanical damage is this post?
One other point to consider is insurance. If you repair/patch, your insurance carrier may have something to say about the method and extent. You might want to give them a call rather than possibly doing the job twice.

Griffy

 

[btrueblood]

Yes, the asphalt coating method is cumbersome, and only works with parts not welded to structures, and parts that can be manipulated/rotated with available equipment (and that can fit in available ovens).

Not sure how you can hot-dip galvanize the inside of a seal-welded cavity? Similarly for filling with concrete, or poly foam - these approaches all leave an unsealed port somewhere on the part, with the subsequent potential for water ingress along the seam between pipe & filler. At least the polyfoam is less likely to crack and allow water to migrate in. I could see using PU foam with a slow rise rate, & seal welding the port after filling, but you will have a gas pocket & possible uncoated part areas afterwards...

Tricky problem. Maybe just use corrosion-resistant alloy...

 

[HgTX]

If it's truly sealed, you wouldn't need to worry about it.

Hot-dip galvanizing is not a repair option but a fabrication option. It would come while the tube's still a tube, before it's fabricated into the rest of the member. You'd get some damage to the galvanizing inside right around the weld, but it's a good start.

Hg

 

[L775]

In general, in building construction, your steel member can fall under on of the two categories. Either exposed to the environmental elements or not (e.g. inside the building envelope)
If the steel member is exposed to the elements then I always specify hot-dip galvanization after fabrication and before delivery to the job site (obviously). In addition to that, I specify that damaged galvanized areas due to handling and field welds be touched up with zinc based rust inhibitive paint.
Regardless where the hallow section is used I always specify it to be filled solid with concrete or grout with high slump 5 to 7" minimum. So far, I have not seen any of my buildings rusting.

 

[HgTX]

Even for beams and arches??

Hg