That’s why ‘classroom’ learning for this profession beats the hell out of online learnin’ all day long!!
Marcel, that would make it look better and might slow or even help prevent future rust, but that sounds more like stabilization than repair.
It seems to me that the question is how much residual strength remains compared to the amount of safety margin designed into the post by whoever specified it.
If someone wanted to know the remaining wall thickness they could drill a few holes in different areas without compromising its structural integrity. By determining the approximate average wall thickness an engineer should be able to calculate whether or not it’s safe.
Need to verify first if it is concrete filled, if it is, than the rust can be removed and repaired by painting which stops the future rusting.
If it is not filled then you can drill a small hole to see if it is worth saving or not. If the wall thickness has been compromised, then it needs replacement.
Judgement call basically.
To much metal gone …
For anyone landing here, there are products out there that do not require this level of work to replace a rusting column with a new ICC code-compliant column. In fact one worker can replace a bad column, start to finish, in 4 hours.
As for rust blisters and rusting columns, there are also specific calculations that can be performed to determine whether the remaining steel can properly bear the vertical loads, and there are several paint prep and application specifications that can be used in a report narrative to ensure the work is performed properly.
If you saw this during a “home” inspection, what would you recommend? remember, it’s a visual inspection, you’re not drilling holes.
As I said to Roy… 
I responded to that post with this;
Need to verify first if it is concrete filled, if it is, than the rust can be removed and repaired by painting which stops the future rusting.
If it is not filled then you can drill a small hole to see if it is worth saving or not. If the wall thickness has been compromised, then it needs replacement.
Judgement call basically
Feel free to explain the procedure.
In fact one worker can replace a bad column, start to finish, in 4 hours.
The photo above? That appears to be more than localized surface rust, but it’s unclear how much of the metal is gone. My advice to a home inspector would be to refer to an engineer. If this then fell in my lap, I’d use my UST meter and measure thickness, and then make a determination based on the load on the column. Safe thing, though, when you see heavy rust and delamination all the way around the circumference, is to recommend replacement. This is my preferred replacement product:
Not quite an item to refer to an engineer that finds procedures with Goggle.
This is a simple residential column.
I’ve removed H-columns under existing buildings without the use of what you are showing.
Did I miss it? Or, is the bottom of the column plate not secured to the concrete, Darren?
OMG Marcel! re earlier comment… lol
what are you referring to? all I saw was an adjustable metal column. Except no footing was shown, most slabs are not thick enough to just install a column on a slab like they showed.
If there was a column removed, there was a footing under it.
There are a couple of ways to install, but chem anchors are the preferred method.
In 4 hours?
I did not see them remove an old column. Should not a replacement column rest directly on top of a footing? even if there is one down below the slab. Are you saying it’s okay to slap a new one right where you cut the old one out at the slab?
The installation instructions that come with the product show that the device is to be installed directly over the sawed off column. This has been approved by the ICC for residential use for almost 10 years.
So, they are secured to the concrete slab and hopefully footing?
That’s the way they were approved for use.