Galvanized stud bolt

[rocio74]

Hi all,

I have a material specification where the stud bolt used for steam, condensate and hot-water at 300 ºC and 20 barg is CK35 galvanized.

I would like to know if the stud bolt material given is ok for these services.

On the other hand, is it possible used the galvanized piping, fittings, bolts, for high temperature services??



Thank you very much,

Regards,
Rocio

 

[ColonelSanders83]

According to the attached file Zinc plating becomes rather useless above 120 C max, it would seem another protective coating may be more usefull.

 

[danbaile]

I would contact your local galvanisers association as a reference point.

I use hot dipped galvanised bolting without any problem at 192 deg c, not sure about 300 though.

http://www.hdg.org.uk/?cms_id=94

 

[SJones]

If the temperature quoted is the fluid temperature, the stud bolt will be at a somewhat lower temperature. Use of galvanised items for corrosion control in a high temperature, say >60 deg C, aqueous environment is not recommended owing to the change in the electrode potential of zinc causing it to become a cathode with respect to steel leading to accelerated corrosion of the steel substrate.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[rocio74]

The temperature quoted is the fluid temperature. The problem is that the material specification says that the bolts used must be CK35 galvanized, however, people of the yard say that the black carbon steel bolts (without any protection) are better than galvanized.

But, is not it better to use galvanized bolts than black carbon steel bolts for this service? and, is not it better the behaviour of the galvanized bolts than black carbon steel under the same environment conditions?

On the other hand, I would like to know if the bolts whose material is A 193 B7 is carbon steel or alloy steel because I don´t understand well the ASTM rule.



Thank you very much,
Rocio

 

[unclesyd]

Yes, A193 B7 is an alloy steel bolt.
Your temperature would normally require an alloy bolt like the A193 B7 or a A193 B16.

What piping code are you installing this piping under?