Corrosion rates for dry galvanized pipe? Please Help!

[paulryan]

Hello,

I am wondering if someone can help, does anyone know where or how I can figure out approximately how much longer Black sch.40 galvanized pipe would last compared to regular Black sch.40 pipe not galvanized. This pipe will almost always be dry?

I have found some information on mm of steel lost per year per 100 liner ft but only for sch 40 water filled pipe but un able to find corrosion rates for dry or galvanized
for dry or galvanized.

 

[gr2vessels]

Paul,
There is no corrosion in terms of metal loss in dry environment, hence the zinc coating does not make any difference. It does make some difference however, in wet or moist environment, in presence of unlimited oxygen. The bare carbon steel may react with the available oxygen to produce the "rust", but the zinc will act as a barrier to the oxygen. The topic is very complex and I encourage you to take some time read about it on the internet and also on this forum, by using the search facility on top of this page.
cheers,
gr2vessels

 

[PEDARRIN2]

What is your application?

What do you mean by "almost always be dry"?

If this is a dry sprinkler pipe - almost always dry might be worse than always wet.

Galvanized pipe works wonders - as long as the the protection doesn't flake - as it might with bad coating or with bad installation.

 

[paulryan]

Thank you for the feedback, the application is a dry sprinkler system. And our client is wondering how much longer a galvanized system would last rather then just installing pipe that is not galvanized, I understand there are many variables that affect the corrosion rate of pipe and I have seen first hand dry systems be subject to corrosion, I am just trying to give them an approximation of the life of the pipe. The system will be tripped once a year for testing, then the water will be drained and other then the condensation that usually occurs on and in the pipe it should remain relatively dry. The type of pipe will be sch 40 black steel. I have done some reading and I do understand the advantages and disadvantages of galvanized pipe. This pipe will be installed in an outdoor parking structure so much of the pipe will be exposed to the elements i.e precipitation ect.

Thanks Paul

 

[strider6]

try this:

Service Life Chart for Hot-Dip Galvanized Coatings

http://www.galvanizeit.org/resources/files/AGA_root/pdf_files/pubs/PR-SLC-05.pdf

http://www.galvanizeit.org/resources/files/AGA_root/pdf_files/pubs/Z-ZC-06.pdf

hope this help u

S

http://www.mindmeister.com/maps/show/6213919

Corrosion Protection & Corrosion Control