connecting galvanized steel to weathering steel 1

[delagina]

i have an existing A242 weathering steel equipment structure,
i will add a new level and will be using A992 ksi galvanized steel.
anything wrong with this?

also end plate moment connection, base plate, etc..may fail later, havent checked yet.

anything wrong with retrofitting weathering plate connection with galvanized steel? say end plate made of weathering steel i will add stiffener or weld additional plate using galvanized steel.

thanks,

 

[csd72]

Look up sacrificial corrosion or sacrificial anode, once you have done this then realise that the galvanising is going to act like one of these. The bigger the piece of waethering steel, the faster the galvanising will diapear.

That is uless you can somehow electrically isolate one from the other. Neoprene washers work for bolts, similar may be available for the steel to steel contacts.

 

[delagina]

cs72, thanks. but i didnt understand well. what should i do? should i suggest using weathering steel also for new steel connecting to existing?

i have a column to column splice because i am adding new level. my original plan was to use A992 galvanized for the splice plate and column connecting to A242 existing column. also plan to use galvanized bolts.

 

[delagina]

also the existing weathering steel was painted black if it makes any difference.

 

[csd72]

A bit of reading:

http://galvanizeit.org/aga/designing-fabricating/design-considerations/dissimilar-metals-in-contact

http://www.galvanizeit.org/images/uploads/drGalv/GalvnizedSteelwithAluminum1995May19.pdf

If the weathering steel is fully painted and then corrosion will probably not be a problem unless there is a significant corrosive content to the atmosphere. It is hard to know for sure without knowing the full details but you need both ends of the corrosive cell to be connected by an ionic medium (moist air could do it) for sacrificial corrosion to take place.