Weathering Steel (Corten, COR-TEN) Fasteners 2

[Michel_Str]

Hi to all

Can you please advise what kind of fasteners (bolts) are applicable to weathering steel (corten, COR-TEN)?
The case is we have some exhaust parts (stack, ducts) to be bolted together and I am aware of proper bolt type selection.

I found that in US, bolt type A325 are designated to weathering steel, but I am in Europe.
The suggestion is to use A4 or A2 bolts. HDG bolts are not in concern because they will corrode for sure.

What is your experiance?

 

[kingnero]

Do you have the possibility of (electrically) isolating the bolts from the mating parts?
If you say exhausts, are there significant temperature changes?
Is this an outside (wet) environment?
Will the corten steel be able to dry, of will there be continuous wet spots (especially at the bolting locations, but anywhere else would also be a bad idea)?

 

[Michel_Str]

thanks for answering

Isolating bolts is not predicted
Temp changes of medium are 50-250 Celsius degrees, but not all the time. Duct can be empty for some time.
It is outside, Norway - by the sea shore. Wet/dry alternately.
If this is outside it can dry after rain, but I assume a bit of water can be trapped between flanges.

 

[kingnero]

With this additional piece of information, I'd advice strongly against A2/A4 bolts and go for a higher grade of stainless (or perhaps a different material all together).

 

[Michel_Str]

Thank you. I will go for A4.
What is interesting... Client says they used DIN 933 St8.8 in a previous projekts and nothing bad happened.

 

[XL83NL]

kingnero has given you sound advice.

8.8 is (low) carbon steel, A4 is stainless steel. You mentioned a seashore environment, yet you don’t seem to understand the impact of stainless fasteners for such applications?

Huub
- You never get what you expect, you only get what you inspect.

 

[dauwerda]

I've never heard good things for weathering steel next to a coastal region either.

 

[Michel_Str]

Ups. Sorry. I misread kingnero post and missed word "against".
Now idea of using A4 has gone.

They are using weathering steel in this plant (costal area) for 15 years with good results. Have no argument against their experience.

 

[TugboatEng]

It is generally not recommended to use cor-ten steel within 2km of coastal regions but there are exceptions. Provided the chloride content of the air is low enough and that varies based on region, the cor-ten can be adequate. With 15 years of good experience I'd say the environment must be suitable.

If you don't want to wait 15 years to determine suitability, there is also this:

airborne chloride levels do not exceed the salinity classification of S2 (i.e. cl < 300mg/m2/day) to BS EN ISO 9223.

 

[TugboatEng]

I also want to add, class 8.8 fasteners usually have a thin zinc coating and the 8.8 steel would also be anodic to the alloyed corten steel. A325 type 3 is specifically for fastening corten. Otherwise, a hot dip galvanized fastener with thick coating can also work.

https://www.cisc-icca.ca/galvanized-bolts-on-weathering-steel/

Fasteners with an inorganic zinc-aluminum coating should also work well and may last longer than the HDG fasteners.