How to identify cor ten (weathering steel) in the field 1

[frogit22]

I am looking at an existing pedestrian bridge.

How do I know if the bridge is constructed using weathering steel or if it is just rusting?

Overall the level of corrosion does not appear alarming.

A secondary question is if it is weathering steel and I need to do some repairs, what are the durability issues with drilling holes or welding the existing weathering steel. Would I be compelled to use weathering steel for any steel repairs or supplementary structural members?

thanks,
Garry

 

[HgTX]

When was it built? Where is it located (dry/humid)?

Hg

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[frogit22]

located over a stream in Connecticut (humid). I do not know the construction date, but it looks an awful lot like a pre-engineered pedestrian bridge - so it may not be too terribly old.

see attached photo.

 

[PEinc]

Look on the bridge for an identification plate or plaque. If it identifies the manufacturer, call and ask questions. I know Continental pedestrian bridges have plates on an end post at each end of the bridge.

 

[PEinc]

The attached file is an example of an identification plate from a pedestrian bridge.

 

[HeavyCivil]

It looks like unpainted steel to me.

 

[TehMightyEngineer]

I also want to say it looks like unpainted steel but it's really hard to tell just from looks. I would suggest having a sample cut from the bridge and sending it away for a metallurgical analysis which should be able to tell you what it's composed of. If it has a large amount of copper (2%) than it's weathering steel, probably ASTM A588 if it's recent.

EIT with BS in Civil/Structural engineering.

 

[HgTX]

It's unpainted, the question is what kind of unpainted.

I would find it hard to believe that a modern "pre-engineered" ped bridge manufacturer would ship an unpainted nonweathering bridge.

If it is weathering steel, then yes, you need to have similar corrosion protection for the rest of the bridge. You *could* replace parts with painted nonweathering steel, but I don't see why you would do that. Use weathering steel and weathering fasteners (A 325 Type 3 bolts, etc.), weathering welding electrodes (AWS D1.1 Table 3.3).

Hg

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[Robertmet]

Looks like weathering steel.That usually had rust that is fairly tightly adhering.
Our bridge across the Delaware here has Cor-Ten griders but the outside, visible parts are painted because the public doesn't want to see a new bridge rusting !!!!

 

[PEinc]

Your bridge looks like a Continental Bridge. I worked on a similar bridge. It was a bit heavier in order to carry golf carts but the details look very similar. It was weathering steel.

 

[PEinc]

And another picture.

 

[Ron]

It appears to be a weathering steel that is not very old...still has a mill scale-like texture. The pattern is too consistent to be typical steel. Unpainted plain steel will exhibit preferential corrosion as well as general corrosion, depending on various conditions. This appears to be all general corrosion as would be expected of weathering steel.

Weathering steel, when its surface is fully developed, exhibits an almost "fuzzy" appearance of light, general corrosion, very uniform in texture and appearance. Some streaking occurs on vertical members, but the corrosion is fairly uniform and protective to the underlying steel.

 

[hokie66]

The pictures PEinc posted certainly look like
CorTen, but the ones Garry posted have a mottled appearance which is to me more like rusting uncoated steel. But I agree with HgTx, it is hard to believe that it would have been shipped unpainted.

 

[frogit22]

One more picture.

I agree it looks like a Continental Bridge - maybe I should call them and see if they have any info.

 

[PEinc]

Every Continental pedestrian bridge I have seen or worked on had the identification plate with a bridge serial number.

 

[HgTX]

The mottling could be because they didn't blast off the mill scale, like Ron said. Blasted WS makes a nice fuzzy brown or maybe orange. WS with mill scale looks pretty crummy, and you can even get pitting where the mill scale flakes off in localized areas; it's just like having a paint defect, for which WS is no better protected than regular steel.

I think ordinary unpainted steel would look a lot nastier than that.

If you pet it, does your hand get rusty?

Hg

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[bridgebuster]

In the first picture everything looks like weathering steel except the bottom chord. IN the second picture the vertical face of the bottom chord has the appearance of WS.

 

[Ron]

HgTX...agree completely.

 

[PEinc]

How can you see the vertical face of the bottom chord in the second picture? It is in a very dark shadow.

 

[bridgebuster]

I got new glasses recently; everything is so much clearer.

Play around with brightness & contrast - you won't get a perfect image but you should be able to see the pattern of the WS patina.