Weathering steel 6

[CivilEngineerUK]

I have a weathering steel column.

1) How to calculate corrosion after 120 years? Any standards to use?

 

[HTURKAK]

You will add C.A.

This quote from SCI .

for a design life of 120 years.]

and the link ,

https://www.steelconstruction.info/Weathering_steel

 

[dik]

A couple of cautions with weathering steel... In an physically active environment where the oxide coating can be abraided, weathering steel can corrode faster than normal steel (I think it oxidizes faster). Also rain on weathering steel can cause rust that will drip to the base below. One tall masonry building had weathering steel for mechanical louvres about 8' from sidewalk level... The rust discoloured the concrete; the louvres were replaced with normal coated steel. I've also seen 'sculptures' made of weathering steel with the same effect.

Dik

 

[CivilEngineerUK]

To avoid abrasion, could it be an idea to weld a stainless steel plate on the weathering profile, where it has contact with other construction parts which moves back and forth?

 

[dik]

These were heavy 24" deep S shapes for the cylinder guides of a floodway control structure in Winnipeg... the abrasion likely came from particles in the water flow.

Dik

 

[kingnero]

Outside? Inside? Exposed to wear/abrasion/impact? Exposed to road salts? Galvanic corrosion (eg. stainless steel bolts)? ...
In 120 yrs, a whole lot can go wrong.

I certainly would not weld SS on a S355W column unless other alternatives (sacrificial wear plates in same/similar material/plastics like ertalon, ...) have been explored.

 

Successful long term weathering of this steel all depends on effective draining of liquid. There are examples of bridges where this has gone horribly wrong.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[dik]

It's not a panacea... and there are a few issues that I've encountered over the years... Bridge problems related to the removal of the 'tight' oxide surfacing?

Dik

 

[dik]

I don't even use SS bolts for HDG material... but, I've seen it done.

Dik

 

[kingnero]

I didn't say it was a good idea...

 

[CivilEngineerUK]

It is outdoor, a post for a noise barriere. Why would you not weld on weathering steel?

 

[kingnero]

I said I wouldn't weld stainless steel on weathering steel, especially not overlap welds to protect the base metal. Not if it is supposed to last for 120 years.

 

[r13]

UK,

I think this is a good reading material maybe you've read already. Pay attention to disadvantages near the end of the article. For its short history from invention to date, 120 years life expectancy is quite a long shot, however, I guess it can be, if you can take proper precautions into your design/application. Link

 

[CivilEngineerUK]

Why is it a bad idea to weld stainless steel on weathering steel? Would you instead weld another weathering steel plate on the main steel column, where the column has contact with another construction part going back and forth?

 

[r13]

I think there is no prohibition on welding stainless steel to the weathering steel, if the proper electrode and welding method/procedure are used. But I wonder why you would consider weld these two metals that having completely different appearance.

 

[EdStainless]

Welding SS to weathering steel is a bad idea for a couple of reasons.
First weathering steels shed a lot of rust, this will wash onto the SS, and in most places this will combine with airborne pollutants and result in attack of the SS. Another reason is that if moisture is ever trapped where the materials meet the steel will suffer accelerated galvanic corrosion attack.
For weathering steels the most critical phase is the first few months. If a good patina forms then things are usually going to work out, but if this gets upset then all bets are off.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[dik]

It's generally a bad idea due to the difference in the metallurgy. Also stainless has different thermal characteristics which makes heating and cooling different leading to cracking. The only time I use stainless and carbon steel is for welding grounding tabs to steel structures used for electrical operations... switch yards, etc. Likely some of the stainless steel whizzes here can add more information.

Dik

 

[r13]

It is may not be a good idea as stated above, but the welding of SS to carbon steel is quite common, with the care of proper welding process/procedures for the mating materials. So that's why I said it is not "prohibited".

 

[r13]

Another reason is that if moisture is ever trapped where the materials meet the steel will suffer accelerated galvanic corrosion attack.

It is a typical concern of welding on weathering steel, not SS only phenomenon, am I wrong?

 

[CivilEngineerUK]

The concrete panel (see figure) will move back and forth, and grind against the weathering column. How would you make that connection, so that abrasion of the steel column will not occur.